EnergyPlus Input Output Reference

This document is intended to be an encyclopedic reference for the EnergyPlus Input Data Dictionary (IDD), Input Data File (IDF) and potential resultant outputs (various output files).

The following descriptions are “grouped” by the elements in the IDD (ref: Getting Started Document and the IDD Conventions). In some cases, the descriptions of reporting will be done for an object (e.g. Lighting electrical consumption or thermal comfort value for a group of people) and in some cases for the entire group (e.g., ambient condition reports).

What’s different about EnergyPlus Input and Output?

The usual procedure for non-interactive programs is to process all the input necessary to “do the job”, perform the actions required by the input, and somewhere along the way produce reports on the actions. Usually, there will be error messages on incorrect input statements and/or incorrect conditions detected during processing. Usually, the input is echoed in its entirety so that the context of errors is shown clearly.

Results are typically output into reports as well as a compilation of various inputs reformatted into different groupings than were originally entered (defaults filled in, etc.)

EnergyPlus does all the above. However, some nuances are different from the usual actions.

EnergyPlus Input Processing

1) EnergyPlus reads the data dictionary (Energy+.idd) and the input data file (in.idf) prior to doing anything else. Only after this is done does processing start. HOWEVER, the input processor only knows as much as the data dictionary has told it. It knows which fields should be alpha and which should be numeric. All of this information (including the IDD) is echoed to the audit file (audit.out) in case errors occur. Most of the errors show up (out of context) in the standard error file (eplusout.err) – there might be enough information to decipher where the error is or you may have to look at the more inclusive audit file. Invalid numeric fields are detected during this processing and default numeric fields are filled. For more information on the IDD, its structure and implications, please see the IDD Conventions discussion below.

2) The biggest difference between EnergyPlus and more traditional input processing is that EnergyPlus is modular in its actual filling in the details for the simulation. Because of the modular structure of EnergyPlus, each module is responsible for “getting” its own input. It receives this input from the input processor in the form of alpha and numeric fields. Each module typically gets all its input the first time it is called. The implication for the user is that error messages may show up in somewhat peculiar places. A further implication is that no order is needed in the input data file! Data that is not needed by a particular simulation is not processed.

3) The data dictionary has the capability to do “automatic” range checking on numeric fields as well as fill in numeric defaults. Both filling in defaults and “automatic” range checking are done when the data is read. Other checks may need a combination of fields and won’t be done until the data is “processed” (after the simulation starts).

4) A couple of other differences that might not be true in other programs: Blanks are significant in alpha fields SO DesignDay is not the same as Design Day (1 space between Design and Day) nor Design Day (2 spaces between Design and Day). Alpha objects, however, are case insensitive SO DesignDay is the same as ‘designday’ or ‘SizingPeriod:DesignDay’.

EnergyPlus Output Processing

1) Unlike the usual formatted output text formatted reports, EnergyPlus usual output is either at the summary or at the detailed (variable) level. Summary reports exist for many inputs as well as sizing results. The more detailed variable level reporting is produced as “stream of consciousness” (as the simulation happens) and must be post-processed for more sensible viewing.

2) Most EnergyPlus reporting can be readily viewed in current spreadsheet programs – or other software that can process “delimited variable” reports. In these kind of reports, each “column” is separated from the next by a “delimiter”. Typical delimiters are “comma” and “tab”. Gradually, EnergyPlus reporting is moving from all comma separated reports to allow the user to select the delimiter via “style” objects.

3) Styled reports allow for more selectable output reporting but also increase the number of output files as we have chosen to create the report names with extensions that typify the actual reporting. Depending on the reporting, these can be:

ü Tab – reports with a .tab extension have tabs as the delimiter. These report files (directly from EnergyPlus) will be named something like “eplus<xxx>.tab” where the <xxx> is a short name of the kind of report (e.g. Zsz for Zone Sizing, Map for Daylighting Map)

ü Csv – reports with a .csv extension have commas as the delimiter. These are also specially formatted for use in spreadsheets (such as the compilation of results from the eplusout.eso file into the eplusout.csv file using the default post-processor program).

ü Txt – reports with a .txt extension have spaces as the “delimiter” but only certain of these are really formatted the way you might expect: where multiple spaces make printing with a non-proportional font would produce readable output.

IDD Conventions

The following is a basic description of the structure of the IDD (it’s actually taken directly from the IDD file). As noted within, ! signifies a comment character as does the \. \ has also been adopted as a convention for including more specific comments about each field in an object. These have been used with success in the IDFEditor and it is hoped the flexibility will provide other interface developers with useful information.

!IDD_Version VERSION NUMBER

! **************************************************************************

! This file is the Input Data Dictionary (IDD) for EnergyPlus.

! The IDD defines the syntax and data model for each type of input "Object."

! Lines in EnergyPlus input files (and IDD) are limited to 500 characters.

! Object Description

! ------------------

! To define an object (a record with data), develop a key word that is unique

! Each data item to the object can be A (Alphanumeric string) or N (numeric)

! Number each A and N. This will show how the data items will be put into the

! arrays that are passed to the Input Processor "Get" (GetObjectItem) routines.

! All alpha fields are limited to 100 characters. Numeric fields should be

! valid numerics (can include such as 1.0E+05) and are placed into double

! precision variables.

! NOTE: Even though a field may be optional, a comma representing that field

! must be included (unless it is the last field in the object). Since the

! entire input is "field-oriented" and not "keyword-oriented", the EnergyPlus

! Input Processor must have some representation (even if blank) for each

! field.

! Object Documentation

! --------------------

! In addition, the following special comments appear one per line and

! most are followed by a value. Comments may apply to a field or the object

! or a group of objects.

! Field-level comments:

! \field Name of field

! (should be succinct and readable, blanks are encouraged)

! \note Note describing the field and its valid values

! \required-field To flag fields which may not be left blank

! (this comment has no "value")

! \begin-extensible Marks the first field at which the object accepts an extensible

! field set. A fixed number of fields from this marker define the

! extensible field set, see the object code \extensible for

! more information.

! \units Units (must be from EnergyPlus standard units list)

! EnergyPlus units are standard SI units

! \ip-units IP-Units (for use by input processors with IP units)

! This is only used if the default conversion is not

! appropriate.

! \unitsBasedOnField For fields that may have multiple possible units, indicates

! the field in the object that can be used to determine

! the units. The field reference is in the A2 form.

! \minimum Minimum that includes the following value

! \minimum> Minimum that must be > than the following value

! \maximum Maximum that includes the following value

! \maximum< Maximum that must be < than the following value

! \default Default for the field (if N/A then omit entire line)

! \deprecated This field is not really used and will be deleted from the object.

! The information is gotten internally within the program.

! \autosizable Flag to indicate that this field can be used with the Auto

! Sizing routines to produce calculated results for the

! field. If a value follows this, then that will be used

! when the "Autosize" feature is flagged. To trigger

! autosizing for a field, enter Autosize as the field's

! value. Only applicable to numeric fields.

! \autocalculatable Flag to indicate that this field can be automatically

! calculated. To trigger auto calculation for a field, enter

! Autocalculate as the field's value. Only applicable to

! numeric fields.

! \type Type of data for the field -

! integer

! real

! alpha (arbitrary string),

! choice (alpha with specific list of choices, see

! \key)

! object-list (link to a list of objects defined elsewhere,

! see \object-list and \reference)

! node (name used in connecting HVAC components)

! \retaincase Retains the alphabetic case for alpha type fields

! \key Possible value for "\type choice" (blanks are significant)

! use multiple \key lines to indicate all valid choices

! \object-list Name of a list of user-provided object names that are valid

! entries for this field (used with "\reference")

! see Zone and BuildingSurface:Detailed objects below for

! examples.

! ** Note that a field may have multiple \object-list commands.

! \reference Name of a list of names to which this object belongs

! used with "\type object-list" and with "\object-list"

! see Zone and BuildingSurface:Detailed objects below for

! examples:

! Zone,

! A1 , \field Name

! \type alpha

! \reference ZoneNames

! BuildingSurface:Detailed,

! A4 , \field Zone Name

! \note Zone the surface is a part of

! \type object-list

! \object-list ZoneNames

! For each zone, the field "Name" may be referenced

! by other objects, such as BuildingSurface:Detailed, so it is

! commented with "\reference ZoneNames"

! Fields that reference a zone name, such as BuildingSurface:Detailed's

! "Zone Name", are commented as

! "\type object-list" and "\object-list ZoneNames"

! ** Note that a field may have multiple \reference commands.

! ** This is useful if the object belongs to a small specific

! object-list as well as a larger more general object-list.

! Object-level comments:

! \memo Memo describing the object

! \unique-object To flag objects which should appear only once in an idf

! (this comment has no "value")

! \required-object To flag objects which are required in every idf

! (this comment has no "value")

! \min-fields Minimum number of fields that should be included in the

! object. If appropriate, the Input Processor will fill

! any missing fields with defaults (for numeric fields).

! It will also supply that number of fields to the "get"

! routines using blanks for alpha fields (note -- blanks

! may not be allowable for some alpha fields).

! \obsolete This object has been replaced though is kept (and is read)

! in the current version. Please refer to documentation as

! to the dispersal of the object. If this object is

! encountered in an IDF, the InputProcessor will post an

! appropriate message to the error file.

! usage: \obsolete New=>[New object name]

! \extensible:<#> This object is dynamically extensible -- meaning, if you

! change the IDD appropriately (if the object has a simple list

! structure -- just add items to the list arguments (i.e. BRANCH

! LIST). These will be automatically redimensioned and used during

! the simulation. <#> should be entered by the developer to signify

! how many of the last fields are needed to be extended (and EnergyPlus

! will attempt to auto-extend the object). The first field of the first

! instance of the extensible field set is marked with \begin-extensible.

! \begin-extensible See previous item, marks beginning of extensible fields in

! an object.

! \format The object should have a special format when saved in

! the IDF Editor with the special format option enabled.

! The options include SingleLine, Vertices, CompactSchedule,

! FluidProperties, ViewFactors, and Spectral.

! The SingleLine option puts all the fields for the object

! on a single line. The Vertices option is used in objects

! that use X, Y and Z fields to format those three fields

! on a single line.

! The CompactSchedule formats that specific object.

! The FluidProperty option formats long lists of fluid

! properties to ten values per line.

! The ViewFactor option formats three fields related to

! view factors per line.

! The Spectral option formats the four fields related to

! window glass spectral data per line.

! \reference-class-name Adds the name of the class to the reference list

! similar to \reference.

! Group-level comments:

! \group Name for a group of related objects

! Notes on comments

! -----------------

! 1. If a particular comment is not applicable (such as units, or default)

! then simply omit the comment rather than indicating N/A.

! 2. Memos and notes should be brief (recommend 5 lines or less per block).

! More extensive explanations are expected to be in the user documentation

IDD – IP Units

In addition, the IDD contains indications of IP (inch-pound) units for the EnergyPlus standard SI (Systems International) units. These may be used by input and output interfaces to display values in the IP system. As noted, if the IP units are “standard” (first block below), then no \ip-units is expected in the field. Note that for some fields – due to their multiple use (for example, schedule values) – there cannot be a ip-unit designation.

! Default IP conversions (no \ip-units necessary)

! m => ft 3.281

! W => Btu/h 3.412

! m3/s => ft3/min 2118.6438

! C => F 1.8 (plus 32)

! kg/J => lb/Btu 2325.83774250441

! Pa => psi 0.0001450377

! W/m-K => Btu-in/h-ft2-F 6.93481276005548

! W/K => Btu/h-F 1.8987

! deltaC => deltaF 1.8

! m2 => ft2 10.764961

! K => R 1.8

! 1/K => 1/R 0.555555556

! (kg/s)/W => (lbm/sec)/(Btu/hr) 0.646078115385742

! J/kg => Btu/lb 0.00042986 (plus 7.686)

! kg-H2O/kg-air => lb-H2O/lb-air 1

! kJ/kg => Btu/lb 0.429925

! lux => foot-candles 0.092902267

! kg/m3 => lb/ft3 0.062428

! kg/s => lb/s 2.2046

! kg/s-m => lb/s-ft 0.67194

! m3 => ft3 35.319837041

! m3 => gal 264.172

! W/m2-K => Btu/h-ft2-F 0.176110194261872

! 1/m => 1/ft 0.304785126485827

! J/kg-K => Btu/lb-F 0.000239005736137667

! J/m3-K => Btu/ft3-F 1.49237004739337E-05

! m/s => ft/min 196.86

! m/s => miles/hr 2.2369

! m2-K/W => ft2-F-hr/Btu 5.678263

! W/m2 => Btu/h-ft2 0.316957210776545

! A/K => A/F 0.555555555555556

! g/kg => grains/lb 7.00000

! g/m-s => lb/ft-s 0.000671968949659

! g/m-s-K => lb/ft-s-F 0.000373574867724868

! J/K => Btu/F 0.000526917584820558

! J/kg-K2 => Btu/lb-F2 0.000132889924714692

! J/m3 => Btu/ft3 2.68096514745308E-05

! kg/kg-K => lb/lb-F 0.555555555555556

! kPa => psi 0.145038

! kPa => inHg 0.29523

! m2/s => ft2/s 10.764961

! m3/kg => ft3/lb 16.018

! m3/m3 => ft3/ft3 1

! N-s/m2 => lbf-s/ft2 0.0208857913669065

! V/K => V/F 0.555555555555556

! W/m-K2 => Btu/h-F2-ft 0.321418310071648

! m3/s-m => ft3/min-ft 645.89

! J/m2-K => Btu/ft2-F 4.89224766847393E-05

! cycles/hr => cycles/hr 1

! kg/kg => lb/lb 1

! J/J => Btu/Btu 1

! g/GJ => lb/MWh 0.00793664091373665

! L/GJ => gal/kWh 0.000951022349025202

! m3/GJ => ft3/MWh 127.13292

! m3/s-m2 => ft3/min-ft2 196.85

! m3/s-person => ft3/min-person 2118.6438

! W/m2-K2 => Btu/h-ft2-F2 0.097826

! g/MJ => lb/MWh 7.93664091373665

! L/MJ => gal/kWh 0.951022349025202

! m3/MJ => ft3/kWh 127.13292

! W/W => Btuh/Btuh 1

! $/m2 => $/ft2 0.0928939733269818

! $ => $ 1

! $/kW => $/(kBtuh/h) 0.293083235638921

! $/m3 => $/ft3 0.0283127014102352

! years => years 1

! $/(W/K) => $/(Btu/h-F) 0.52667614683731

! $/(m3/s) => $/(ft3/min) 0.000472000059660808

! W/m => Btu/h-ft 1.04072

! K/m => F/ft 0.54861322767449

! W/s => W/s 1

! kmol => kmol 1

! J => Wh 0.000277777777777778

! GJ => ton-hrs 78.9889415481832

! kg/m2 => lb/ft2 0.204794053596664

! kg => lb 2.2046

! percent/K => percent/F 0.555555555555556

! kg/s2 => lb/s2 2.2046

! g/mol => lb/mol 0.0022046

! deltaJ/kg => deltaBtu/lb 0.0004299

! person/m2 => person/ft2 0.0928939733269818

! m2/person => ft2/person 10.764961

! W/person => Btu/h-person 3.412

! m3/person => ft3/person 35.319837041

! m3/hr-person => ft3/hr-person 35.319837041

! m3/m2 => ft3/ft2 3.281

! m3/hr-m2 => ft3/hr-ft2 3.281

! m3/hr => ft3/hr 35.319837041

! s/m => s/ft 0.304785126485827

! m2/m => ft2/ft 3.281

! L/day => pint/day 2.11337629827348

! L/kWh => pint/kWh 2.11337629827348

! kg/Pa-s-m2 => lb/psi-s-ft2 1412.00523459398

! m/hr => ft/hr 3.281

! Mode => Mode 1

! Control => Control 1

! Availability => Availability 1

! rev/min => rev/min 1

! W/(m3/s) => W/(ft3/min) 0.0004719475

! VA => VA 1

! N-m => lbf-in 8.85074900525547

! m3/s-W => ft3-h/min-Btu 621.099127332943

! cm2 => inch2 0.15500031000062

! kg/m => lb/ft 0.67196893069637

! m/yr => inch/yr 39.37

! Other conversions supported (needs the \ip-units code)

! m => in 39.37

! W => W 1

! m3/s => gal/min 15852

! m3/s => lbH2O/hr 7936289.998

! Pa => inHg 0.00029613

! Pa => inH2O 0.00401463

! Pa => ftH2O 0.00033455

! W/person => W/person 1

! W/m2 => W/m2 1

! W/m2 => W/ft2 0.0928939733269818

! W/m-K => Btu/h-ft-F 0.577796066000163

! Units fields that are not translated

! deg

! hr

! A

! dimensionless

! V

! ohms

! A/V

! eV

! percent

! s

! W/m2 or deg C

! W/m2, W or deg C

! minutes

! 1/hr

! **************************************************************************

Input – Output Descriptions (Document)

Input Descriptions

In the descriptions below, the fields for each input object will be described. Refer to the Energy+.idd for complete specifications. Energy+.idd is a text file that can be viewed with many text editors or word processors. The Site:Location object will serve as an example.

First, the object name is given. (Site:Location) This is followed by a comma in both the definition (IDD) and in an input file (IDF). In fact, all fields except the terminating field of an IDD class object and IDF object are followed by commas. The final field in an IDD class object or in an IDF object is terminated by a semi-colon.

Next is an alpha field, the location name. As noted above, for input, spaces are significant in this field. The main inputs for Site:Location are numeric fields. These are numbered (as is the alpha field) for convenience. The \ designations will show various information about the objects as described above in the IDD conventions discussion. Of importance for reading this document are the units and possible minimum and maximum values for a field.

There is automatic processing of the \minimum, \maximum and \default data for numeric fields. Any infractions of the \minimum, \maximum fields are automatically detected and messages will appear in the standard error file. After all the input is checked, infractions will cause program termination (before the bulk of the simulation is completed). Defaults are also enforced if you leave the numeric field blank.

Some objects need all the parameters listed by the definition; some do not. In the descriptions that follow, we will try to indicate which parts are optional. Usually, these will be the last fields in the object input or definition. Even if items are not used for a particular object (e.g. Multiplier in the FenestrationSurface:Detailed and type=Door), the field must be included unless it is the last field in the object. So, for this instance, one must include a multiplier field (must be numeric and would need to obey any \minimum, \maximum rules) for doors.

n ExampleFiles.xls – shows many details about the included example files including highlights of features.

n ExampleFiles-ObjectsLink.xls – shows, for each object, the first three occurrences of that object in an example file.

Output Descriptions

In the descriptions below, we will endeavor to have each object’s output displayed as well as each of the outputs described. The output variables for a run are selected by choosing the Output:VariableDictionary object. This object displays the available output variables for a run on the eplusout.rdd (regular variables) and eplusout.mdd (meter variables) files. Two significant styles are available for these displays and the descriptions below may have one for some objects and another for other objects. The variables are the same but will look a bit different. For clarity, the two displays are shown below:

Note that the IDF-Editor can interpret both sets of files and assist you in getting output variables into your input files. But you will have to successfully run your input file first.

The Simple (or regular) display looks like the following figure and is interpreted:

Zone/HVAC – when the output is produced at the “Zone” timestep (ref: number of timesteps in each hour) or at the “HVAC” aka System timestep (which can vary for each hour).

Average/Sum – whether this is a averaged value over the reporting period (such as a temperature or rate) or whether this is a summed value over the reporting period. Reporting periods are specified in the Output:Variable or Output:Meter objects.

<Variable Name> -- The variable name one uses for reporting is displayed (e.g., Outdoor Dry Bulb) along with the units (e.g., [C]).

Note that the eplusout.mdd file is similar, but meters are only available at the Zone timestep.

The IDF display has all the same information in an IDF-ready form (i.e., you could copy and paste it into your input file using a text editor).

All of the same information appears in a slightly different form and defaults to “hourly” reporting frequency (which, of course, can be changed when you put it into your input file). The “*” is preselected so that you would be reporting for all those items.

Group -- Simulation Parameters

Version

Field: Version Identifier

The Version object allows you to enter the proper version that your IDF was created for. This is checked against the current version of EnergyPlus and a Severe error issued (non-terminating) if it does not match the current version string. Note that versions are often significant and there is no guarantee that the older file will run in the newer versions of the program. See IDF Version Updater (Auxiliary Programs Document) for methods of changing the older files to newer versions.

Timestep

Field: Number of Timesteps per Hour

The Timestep object specifies the "basic" timestep for the simulation. The value entered here is usually known as the Zone Timestep. This is used in the Zone Heat Balance Model calculation as the driving timestep for heat transfer and load calculations. The value entered here is the number of timesteps to use within an hour. Longer length timesteps have lower values for Number of Timesteps per Hour. For example a value of 6 entered here directs the program to use a zone timestep of 10 minutes and a value of 60 means a 1 minute timestep. The user’s choice for Number of Timesteps per Hour must be evenly divisible into 60; the allowable choices are 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60.

The choice made for this field has important implications for modeling accuracy and the overall time it takes to run a simulation. Here are some considerations when choosing a value:

· The solution technique used in EnergyPlus has been designed to be stable with zone timesteps of up to sixty minutes (Number Timesteps in Hour = 1). However, 60 minutes is considered a “long” timestep and it should only be used in rare occasions where there is no HVAC system, accuracy is not a concern, and short run times are critical. Such long timesteps are not recommended to use because simulation results are more accurate for shorter timesteps, of say 10 minutes or less (Number of Timesteps per Hour of 6 or more). Shorter zone timesteps improve the numerical solution of the Zone Heat Balance Model because they improve how models for surface temperature and zone air temperature are coupled together. Longer timesteps introduce more lag and lead to more a dampened dynamic response.

· Simulation run time increases with shorter timesteps or larger values for Number of Timesteps per Hour. The effect varies with the nature of the model. The user can test out different values on their particular model to understand the implications for his or her particular case. Sometimes large models with multizone HVAC and Plant systems execute nearly as fast with 15 minute timesteps as with 60 minute timesteps because fewer iterations are required in the system modeling since the prior timestep’s results are close to the final outcome of next timestep.

· The weather data files usually have 60-minute (or hourly) data. However, it does not follow that this should be used as the basis for choosing the zone timestep because:

o EnergyPlus carefully interpolates the weather data between data points for use at shorter timesteps. This is discussed in a later section: Weather Data Hourly Interpolation

o Many aspects of a model have time scales that differ from the that of the weather data. A goal of the modeling is to predict how the building will respond to the weather. However, the building’s response is not governed by the time scale that the weather data are available at, but rather the time scales of the dynamic performance of the thermal envelope as well as things like schedules for internal gains, thermostats, and equipment availability.

· If the model will include calculating the cost of electricity, then the user should be aware that many electric utility tariffs base charges on demand windows of a specified length of time. If the choice of Number of Timesteps per Hour is not consistent with the demand window, then unexpected results may be obtained. For reasonable prediction of the maximum rates for electricity use for in calculating demand charges, the length of the zone timestep needs to be consistent with the tariff’s demand window. The following table lists what values are consistent with various demand windows.

There is also second type of timestep inside EnergyPlus that is known as the System Timestep. This is a variable-length timestep that governs the driving timestep for HVAC and Plant system modeling. The user cannot directly control the system timestep (except by use of the ConvergenceLimits object). When the HVAC portion of the simulation begins its solution for the current zone timestep, it uses the zone timestep as its maximum length but then can reduce the timestep, as necessary, to improve the solution. The technical details of the approach are explained in the Engineering Documentation under "Integrated Solution Manager".

Users can see the system timestep used if they select the "detailed" frequency option on an HVAC report variable (e.g. Zone/Sys Air Temperature). To contrast, the "Zone" variables will only be reported on the zone timestep (e.g. Zone Mean Air Temperature).

Suggested defaults are 4 for non-HVAC simulations, 6 for simulations with HVAC, 20 is the minimum for ConductionFiniteDifference and HeatAndMoistureFiniteElement simulations. Green roof (ref: Material:RoofVegetation) also may require more timesteps.

ConvergenceLimits

This item is an “advanced” feature that should be used only with caution. It is specifically included to assist some users “speed up” calculations while not overly compromising accuracy. The user must judge for him/herself whether the reduced run time is useful.

Field: Minimum System Timestep

Usually the minimum system timestep is allowed to vary from the zone timestep (as maximum) to a minimum timestep of 1 minute during certain system calculations. This might be when the system turns on or off, for example. Entering 0 in this field sets the minimum system timestep to be the same as the zone timestep. Otherwise the units of the field are minutes. It’s probably a good idea to have any minimum entered be a divisor of the zone timestep.

Field: Maximum HVAC Iterations

The HVAC Manager will iterate to a solution or up to a set number of iterations. If not “converged”, then a warning error appears:

In order to reduce time used in simulating your building, you may choose to enter a lesser number than the default of 20 for the maximum number of iterations to be used. Or, you may wish to enter a bigger number for certain buildings. To get more information printed with a “max iteration” message, you need to enter a “Output:Diagnostics, DisplayExtraWarnings;” command (which may also generate other warnings than just this one).

Building

The Building object describes parameters that are used during the simulation of the building. There are necessary correlations between the entries for this object and some entries in the Site:WeatherStation and Site:HeightVariation objects, specifically the Terrain field.

Field: Building Name

Field: North Axis

The Building North Axis is specifiedrelative to true North. Buildings frequently do not line up with true north. For convenience, one may enter surfaces in a “regular” coordinate system and then shift them via the use of the North Axis. The value is specified in degrees from “true north” (clockwise is positive).

The figure below shows how the building north axis can be rotated to correspond with one of the major axes of an actual building. The relevance of this field is described more completely under “GlobalGeometryRules”; in particular, the value of “North Axis” is ignored if a coordinate system other than “relative” is used.

Field: Terrain

The site’s terrain affects how the wind hits the building – as does the building height. In addition, the external conduction method usually has its own parameters for the calculation. Please see the Engineering Documentation, External Conduction section for particulars. The legal values for this field are shown in the following table.

Warmup Convergence

The following two fields along with the minimum and maximum number of warmup days (also in this object) define the user specified criteria for when EnergyPlus will “converge” at each environment (each sizing period or run period set as Yes in the SimulationControl object). EnergyPlus “runs” the first day of the environment (starting with a set of hard-coded initial conditions) until the loads/temperature convergence tolerance values are satisfied (next two fields) or until it reaches “maximum number of warmup days”. Note that setting the convergence tolerance values too loose will cause the program to be satisifed too early and you may not get the results you expect from the actual simulation.

Field: Loads Convergence Tolerance Value

This value represents the number at which the loads values must agree before “convergence” is reached. Loads tolerance value is a fraction of the load.

Field: Temperature Convergence Tolerance Value

This value represents the number at which the zone temperatures must agree (from previous iteration) before “convergence” is reached. (Units for this field is delta C).

Convergence of the simultaneous heat balance/HVAC solution is reached when either the loads or temperature criterion is satisfied.

All tolerances have units so the temperature tolerance is in degrees C (or degrees K) and the loads tolerance is in Watts. Both tolerances work the same way, just one looks at temperatures and one looks at heating and cooling loads. After the second warm-up day, the program compares the maximum temperature experienced in a space with the maximum temperature from the previous day. If those two temperatures are within the tolerance, then it has passed the first warm-up check.

It does a similar comparison with lowest temperatures experience within all the zones. If the current simulation day and the previous day values are within the tolerance, then it has passed the second warm-up check. Similar things are done with the loads tolerance and the maximum heating and cooling loads that are experienced within the spaces. Those are compared individually to the values for the previous day. If they are both in tolerance, then the simulation has passed the third and fourth warm-up check. The simulation stays in the warm-up period until ALL FOUR checks have been passed.

Please note--other "convergence tolerance" inputs are required for certain HVAC equipment (unit ventilator, unit heater, window AC, etc.). The purpose and units of these parameters are different from "load convergence tolerance" and "temperature convergence tolerance" in the BUILDING object.

Field: Solar Distribution

Setting this value determines how EnergyPlus treats beam solar radiation and reflectances from exterior surfaces that strike the building and, ultimately, enter the zone. There are five choices: MinimalShadowing, FullExterior and FullInteriorAndExterior, FullExteriorWithReflections, FullInteriorAndExteriorWithReflections.

In this case, there is no exterior shadowing except from window and door reveals. All beam solar radiation entering the zone is assumed to fall on the floor, where it is absorbed according to the floor's solar absorptance. Any reflected by the floor is added to the transmitted diffuse radiation, which is assumed to be uniformly distributed on all interior surfaces. If no floor is present in the zone, the incident beam solar radiation is absorbed on all interior surfaces according to their absorptances. The zone heat balance is then applied at each surface and on the zone's air with the absorbed radiation being treated as a flux on the surface.

In this case, shadow patterns on exterior surfaces caused by detached shading, wings, overhangs, and exterior surfaces of all zones are computed. As for MinimalShadowing, shadowing by window and door reveals is also calculated. Beam solar radiation entering the zone is treated as for MinimalShadowing -- All beam solar radiation entering the zone is assumed to fall on the floor, where it is absorbed according to the floor's solar absorptance. Any reflected by the floor is added to the transmitted diffuse radiation, which is assumed to be uniformly distributed on all interior surfaces. If no floor is present in the zone, the incident beam solar radiation is absorbed on all interior surfaces according to their absorptances. The zone heat balance is then applied at each surface and on the zone's air with the absorbed radiation being treated as a flux on the surface.

This is the same as FullExterior except that instead of assuming all transmitted beam solar falls on the floor the program calculates the amount of beam radiation falling on each surface in the zone, including floor, walls and windows, by projecting the sun's rays through the exterior windows, taking into account the effect of exterior shadowing surfaces and window shading devices.

If this option is used, you should be sure that the surfaces of the zone totally enclose a space. This can be determined by viewing the eplusout.dxf file with a program like AutoDesk’s Volo View Express. You should also be sure that the zone is convex. Examples of convex and non-convex zones are shown in Figure 2. The most common non-convex zone is an L-shaped zone. (A formal definition of convex is that any straight line passing through the zone intercepts at most two surfaces.) If the zone’s surfaces do not enclose a space or if the zone is not convex you should use Solar Distribution = FullExterior instead of FullInteriorAndExterior.

If you use FullInteriorAndExterior the program will also calculate how much beam radiation falling on the inside of an exterior window (from other windows in the zone) is absorbed by the window, how much is reflected back into the zone, and how much is transmitted to the outside. In this calculation the effect of a shading device, if present, is accounted for.

If using reflections, the program calculates beam and sky solar radiation that is reflected from exterior surfaces and then strikes the building. These reflecting surfaces fall into three categories:

1) Shadowing surfaces. These are surfaces like overhangs or neighboring buildings entered with Surface Shading:Site:Detailed, Shading:Building:Detailed, or Shading:Zone:Detailed. See Figure 3.

2) These surfaces can have diffuse and/or specular (beam-to-beam) reflectance values that are specified with the Shading Surface Reflectance object (ref: ShadingProperty:Reflectance).

3) Exterior building surfaces. In this case one section of the building reflects solar radiation onto another section (and vice-versa). See Figure 4.

4) The building surfaces are assumed to be diffusely reflecting if they are opaque (walls, for example) and specularly reflecting if they are windows or glass doors. The reflectance values for opaque surfaces are calculated by the program from the Solar Absorptance and Visible Absorptance values of the outer material layer of the surface’s construction (ref: Material properties). The reflectance values for windows and glass doors are calculated by the program from the reflectance properties of the individual glass layers that make up surface’s construction assuming no shading device is present and taking into account inter-reflections among the layers (ref: Window Properties).

5) The ground surface. Reflection from the ground is calculated even if reflections option is not used. But in this case the ground plane is considered unobstructed, i.e., the shadowing of the ground by the building itself or by obstructions such as neighboring buildings is ignored. This shadowing is taken into account if the reflections option is used.[1] This is shown in Figure 5.

Figure 3. Solar reflection from shadowing surfaces. Solid arrows are beam solar radiation; dashed arrows are diffuse solar radiation. (a) Diffuse reflection of beam solar radiation from the top of an overhang. (b) Diffuse reflection of sky solar radiation from the top of an overhang. (c) Beam-to-beam (specular) reflection from the façade of an adjacent highly-glazed building represented by a vertical shadowing surface.

Figure 4. Solar reflection from building surfaces onto other building surfaces. In this example beam solar reflects from a vertical section of the building onto a roof section. The reflection from the window is specular. The reflection from the wall is diffuse.

Figure 5. Shadowing from building affects beam solar reflection from the ground. Beam-to-diffuse reflection from the ground onto the building occurs only for sunlit areas, A and C, not from shaded area, B.

Field: Maximum Number of Warmup Days

This field specifies the number of “warmup” days that might be used in the simulation before “convergence” is achieved. The default number, 25, is usually more than sufficient for this task; however, some complex buildings (with complex constructions) may require more days. An error message will occur when the simulation “runs” out of days, fort each zone:

As noted in the message, there will be more information in the .eio file. (Refer to Output Details document as well for examples.)

You may be able to increase the Maximum Number of Warmup Days and get convergence, but some anomalous buildings may still not converge. Simulation proceeds for x warmup days until “convergence” is reached (see the discussion under the Temperature Convergence Tolerance Value field in this object, just above).

Field: Minimum Number of Warmup Days

The minimum number of warmup days that produce enough temperature and flux history to start EnergyPlus simulation for all reference buildings was suggested to be 6. When this field is greater than the maximum warmup days defined previous field the maximum number of warmup days will be reset to the minimum value entered here. Warmup days will be set to be the value you entered when it is less than the default 6. The selection of 6 as a minimum was done after careful study using the 400+ test suite files that we use in development.

SurfaceConvectionAlgorithm:Inside

This input object is used control the choice of models used for surface convection at the inside face of all the heat transfer surfaces in the model. This object sets the selection for convection correlations in a global way. The Zone Inside Convection Algorithm input field in the Zone object may be used to selectively override this value on a zone-by-zone basis. Further, individual surfaces can refine the choice by each surface or surface lists – see object SurfaceProperty:ConvectionCoefficients and object SurfaceProperty:ConvectionCoefficients:MultipleSurface.

Field: Algorithm

The model specified in this field is the default algorithm for the inside face all the surfaces.. The key choices are Simple, TARP, CeilingDiffuser, and AdaptiveConvectionAlgorithm.

The Simple model applies constant heat transfer coefficients depending on the surface orientation.

The TARP model correlates the heat transfer coefficient to the temperature difference for various orientations. This model is based on flat plate experiments.

The CeilingDiffuser model is a mixed and forced convection model for ceiling diffuser configurations. The model correlates the heat transfer coefficient to the air change rate for ceilings, walls and floors. These correlations are based on experiments performed in an isothermal room with a cold ceiling jet. To avoid discontinuities in surface heat transfer rate calculations, all of correlations have been extrapolated beyond the lower limit of the data set (3 ACH) to a natural convection limit that is applied during the hours when the system is off.

The AdaptiveConvectionAlgorithm model is an dynamic algorithm that organizes a large number of different convection models and automatically selects the one that best applies. The adaptive convection algorithm can also be customized using the SurfaceConvectionAlgorithm:Inside:AdaptiveModelSelections input object. These models are explained in detail in the EnergyPlus Engineering Reference Document. The default is AdaptiveConvectionAlgorithm.

SurfaceConvectionAlgorithm:Outside

Various exterior convection models may be selected for global use. The optional Zone Outside Convection Algorithm input field in the Zone object may be used to selectively override this value on a zone-by-zone basis. Further, individual surfaces can refine the choice by each surface or surface lists – see object SurfaceProperty:ConvectionCoefficients and object SurfaceProperty:ConvectionCoefficients:MultipleSurface.

Field: Algorithm

The available key choices are SimpleCombined, TARP, MoWiTT, DOE-2, and AdaptiveConvectionAlgorithm.

The Simple convection model applies heat transfer coefficients depending on the roughness and windspeed. This is a combined heat transfer coefficient that includes radiation to sky, ground, and air. The correlation is based on Figure 1, Page 25.1 (Thermal and Water Vapor Transmission Data), 2001 ASHRAE Handbook of Fundamentals. Note that if Simple is chosen here or in the Zone field and a SurfaceProperty:ConvectionCoefficients object attempts to override the caulcation with a different choice, the action will still be one of combined calculation. To change this, you must select one of the other methods for the global default.

All other convection models apply heat transfer coefficients depending on the roughness, windspeed, and terrain of the building’s location. These are convection only heat transfer coefficients; radiation heat transfer coefficients are calculated automatically by the program.

The TARP algorithm was developed for the TARP software and combines natural and wind-driven convection correlations from laboratory measurements on flat plates.

The DOE-2 and MoWiTT were derived from field measurements. DOE-2 uses a correlation from measurements by Klems and Yazdanian for rough surfaces. MoWitt uses a correlation from measurements by Klems and Yazdanian for smooth surfaces and, therefore, is most appropriate for windows (see SurfaceProperty:ConvectionCoefficients:MultipleSurface for how to apply to only windows).

The AdaptiveConvectionAlgorithm model is an dynamic algorithm that organizes a large number of different convection models and automatically selects the one that best applies. The adaptive convection algorithm can also be customized using the SurfaceConvectionAlgorithm:Outside:AdaptiveModelSelections input object. All algorithms are described more fully in the Engineering Reference.

HeatBalanceAlgorithm

The HeatBalanceAlgorithm object provides a way to select what type of heat and moisture transfer algorithm will be used across the building construction calculations.

Field: Algorithm

n The ConductionTransferFunction selection is a sensible heat only solution and does not take into account moisture storage or diffusion in the construction elements.

n The MoisturePenetrationDepthConductionTransferFunction selection is a sensible heat diffusion and an inside surface moisture storage algorithm that also needs additional moisture material property information. Sometimes, this is referred to as the Effective Moisture Penetration Depth or EMPD. See the moisture material property object for additional information and description of outputs:

n Advanced/Research usage: The ConductionFiniteDifference selection is a sensible heat only solution and does not take into account moisture storage or diffusion in the construction elements. This solution technique uses a 1-D finite difference solution in the construction elements. Outputs for the surfaces are described with the material property objects. The Conduction Finite Difference (aka CondFD) property objects are:

n Advanced/Research usage: The ConductionFiniteDifferenceSimplified selection is a sensible heat only solution and does not take into account moisture storage or diffusion in the construction elements. This solution technique uses a 1-D finite difference solution in the construction elements – representing only two nodes per construction. Outputs for the surfaces are described with the material property objects. The Conduction Finite Difference Simplified property objects are:

n Advanced/Research usage: The CombinedHeatAndMoistureFiniteElement is a coupled heat and moisture transfer and storage solution. The solution technique uses a one dimensional finite difference solution in the construction elements and requires further material properties described in the Heat and Moisture Transfer material properties objects. Outputs from the algorithm are described with these objects. The Heat and Moisture Transfer property objects are:

Field: Surface Temperature Upper Limit

This field is a bit “advanced”. It should only be used when the simulation fails AND you cannot determine a cause for the failure. That is, you receive an error similar to:

And, after careful perusal, you cannot find a solution as suggested in the error description. You may then want to enter a higher number than the default for this field.

Field: Minimum Surface Convection Heat Transfer Coefficient Value

This optional field is used to set an overall minimum for the value of the coefficient for surface convection heat transfer (Hc) in W/m2-K. A minimum is necessary for numerical robustness because some correlations for Hc can result in zero values and create numerical problems. This field can be used to support specialized validation testing to suppress convection heat transfer and to investigate the implications of different minimum Hc values. The default is 0.1.

Field: Maximum Surface Convection Heat Transfer Coefficient Value

This optional field is used to set an overall maximum for the value of the coefficient for surface convection heat transfer (Hc) in W/m2-K. High Hc values are used in EnergyPlus to approximate fixed surface temperature boundary conditions. This field can be used to alter the accepted range of user-defined Hc values.

HeatBalanceSettings:ConductionFiniteDifference

This object is used to control the behavior of the Conduction Finite Difference algorithm for surface heat transfer. The settings are global and affect how the model behaves for all the surfaces.

Field: Difference Scheme

This field determines the solution scheme used by the Conduction Finite Difference model. There are two options CrankNicholsonSecondOrder and FullyImplicitFirstOrder. The CrankNicholsonSecondOrder scheme is second order in time and may be faster. But it can be unstable over time when boundary conditions change abruptly and severely. The FullyImplicitFirstOrder scheme is first order in time and is more stable over time. But it may be slower.

Field: Space Discretization Constant

This field controls the how the model determines spatial discretization, or the count of nodes across each material layer in the construction. The model calculates the nominal distance associated with a node,

, using

The default is 3. Typical values are from 1 to 3. Lower values for this constant lead to more nodes and finer-grained space discretization.

Field: Relaxation Factor

The finite difference solver includes under-relaxation for improved stability for interactions with the other surfaces. This input field can optionally be used to modify the starting value for the relaxation factor. Larger numbers may solve faster, while smaller numbers may be more stable. The default is 1.0. If the program detects numerical instability, it may reduce the value entered here to something lower and more stable.

Field: Inside Face Surface Temperature Convergence Criteria

The surface heat balance model at the inside face has a numerical solver that uses a convergence parameter for a maximum allowable differences in surface temperature. This field can optionally be used to modify this convergence criteria. The default value is 0.002 and was selected for stability. Lower values may further increase stability at the expense of longer runtimes, while higher values may decrease runtimes but lead to possible instabilities. The units are in degrees Celsius.

ZoneAirHeatBalanceAlgorithm

The ZoneAirHeatBalanceAlgorithm object provides a way to select what type of solution algorithm will be used to calculate zone air temperatures and humidity ratios. This object is an optional object. If the default algorithm is used, this object is not required in an input file.

Field: Algorithm

Three choices are allowed to select which solution algorithm will be used. The ThirdOrderBackwardDifference selection is the default selection and uses the third order finite difference approximation to solve the zone air energy and moisture balance equations. The AnalyticalSolution selection uses the integration approach to solve the zone air energy and moisture balance equations. The EulerMethod selection uses the first order finite backward difference approximation to solve the zone air energy and moisture balance equations.

ZoneAirContaminantBalance

The ZoneAirContaminantBalance object provides a way to select which contaminant type will be simulated. Currently the only available contaminant is carbon dioxide. The ability to model other contaminants will be added later. This object is optional, only required in the input data file if the user wishes to model contaminant concentration levels as part of their simulation.

Field: Carbon Dioxide Concentration

Input is Yes or No. The default is No. If Yes, simulation of carbon dioxide concentration levels will be performed. If No, simulation of carbon dioxide concentration levels will not be performed.

Field: Outdoor Carbon Dioxide Schedule Name

This field specifies the name of a schedule that contains outdoor air carbon dioxide level values in units of ppm. One source of monthly average CO₂ levels in the atmosphere is available at a NOAA ftpsite as ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt.

Carbon Dioxide Outputs

The following output variable is available when Carbon Dioxide Concentration = Yes.

Zone Air Carbon Dioxide Concentration [ppm]

This report variable represents the carbon dioxide concentration level in parts per million (ppm) for each zone. This is calculated and reported from the Correct step in the Zone Air Contaminant Predictor-Corrector module.

ShadowCalculation

In order to speed up the calculations, shadowing calculations (sun position, etc.) are performed over a period of days. Note that this value may be very important for determining the amount of sun entering your building and by inference the amount of cooling or heating load needed for maintaining the building. Though termed “shadowing” calculations, it in affect determines the sun position for a particular day in a weather file period simulation. (Each design day will use the date of the design day object). Even though weather file data contains the amount of solar radiation, the internal calculation of sun position will govern how that affect various parts of the building. By default, this is every 20 days throughout a weather run period.

Field: Calculation Frequency

This numeric field will cause the shadowing calculations to be done periodically using the number in the field as the number of days in each period. Using this field will allow you to synchronize the shadowing calculations with changes in shading devices. Using the default of 20 days in each period is the average number of days between significant changes in solar position angles. For these shadowing calculations, an “average” (over the time period) of solar angles, position, equation of time are also used.

Field: Maximum Figures in Shadow Overlap Calculations

This numeric field will allow you to increase the number of figures in shadow overlaps. Due to the shadowing algorithm, the number of shadows in a figure may grow quite large even with fairly reasonable looking structures. Of course, the inclusion of more allowed figures will increase calculation time. Likewise, too few figures may not result in as accurate calculations as you desire.

Field: Polygon Clipping Algorithm

This is an advanced feature. Prior to V7, the internal polygon clipping method was a special case of the Weiler-Atherton method. Now, two options are available: SutherlandHodgman (default) and ConvexWeilerAtherton. Theoretically, Sutherland-Hodgman is a simpler algorithm but it works well in cases where receiving surfaces (of shadows) are non-convex. The Weiler-Atherton implementation is only accurate where both casting and receiving surfaces are convex. Warnings/severe errors are displayed when necessary. More details on polygon clipping are contained in the Engineering Reference.

Field: Sky Diffuse Modeling Algorithm

Two choices are available here: SimpleSkyDiffuseModeling and DetailedSkyDiffuseModeling. SimpleSkyDiffuseModeling (default) performs a one-time calculation for sky diffuse properties. This has implications if you have shadowing surfaces with changing transmittance (i.e. not all opaque or not all transparent) during the year. The program checks to see if this might be the case and automatically selects DetailedSkyDiffuseModeling if the shading transmittance varies. Even if the transmittance doesn’t vary and the option for detailed modeling is used, that option is retained (though it will increase execution time) because you may be using EMS to vary the transmittance. When the detailed modeling is done, there will be a warning posted if the Calculation Frequency (above) is > 1.

In general (and you should also read the previous field description), if shadowing surfaces are used with the transmittance property, the user should be careful to synchronize this calculation with the scheduled occurrence of the transmittance (if any) (or use 1, which will be the most accurate but will cause more time in the calculations).

Output:Diagnostics

Sometimes, messages only confuse users – especially new users. Likewise, sometimes certain report variables exist for only a certain condition but some take them at face value/name. Some features may be very important but under certain instances cause problems. Thus, we have added the diagnostic output object to be able to turn on or off certain messages, variables, and features depending on conditions.

Both fields of the Output:Diagnostics command can accept all the applicable keys. More than one object may be entered.

Field: key1, key2

DisplayAllWarnings – use this to get all warnings (except the developer warnings “DisplayZoneAirHeatBalanceOffBalance”). This key sets all other display warning values to on.

DisplayExtraWarnings – use this to get all extra warnings. An example of an extra warning is when a user enters a ceiling height or volume with the Zone object and EnergyPlus calculates something significantly different based on the entered zone geometry.

DisplayUnusedSchedules – use this to have the unused schedules (by name) listed at the end of the simulation.

DisplayUnusedObjects – use this to have unused (orphan) objects (by name) listed at the end of the simulation.

DisplayAdvancedReportVariables – use this to be able to use the “Opaque Surface Inside Face Conduction” – the name may be misleading to some. If you put in this field, then you will be able to report on this variable.

DisplayZoneAirHeatBalanceOffBalance – this is a developer diagnostic which you can turn on, if you desire.

DoNotMirrorDetachedShading – use this to turn off the automatic mirroring of detached shading surfaces. These surfaces are automatically mirrored so that the user does not need to worry about facing direction of the surface and the shading surface will shade the building as appropriate. Note that Shading:Zone:Detailed surfaces are also mirrored and there is no way to turn that “off”.

DisplayWeatherMissingDataWarnings – use this to turn on the missing data warnings from the read of the weather file.

ReportDuringWarmup – use this to allow reporting during warmup days. This can show you exactly how your facility is converging (or not) during the initial “warmup” days of the simulation. Generally, only developers or expert simulation users would need this kind of detail.

Output:DebuggingData

There may be times when a particular input file requires additional debugging. The Output:DebuggingData object may be used to report all available node data (e.g., temperature, mass flow rate, set point, pressure, etc.). The debug data is reported to the DBG text file. The debug file first reports the node number and name, and then all available node information for each zone time step (Ref. Timestep).

The 2 fields of the Output:DebuggingData object can accept either a 1 (turn on) or any other value (turn off). Only one object may be entered.

Field: Report Debugging Data

This field turns on debug reporting when a value of 1 is entered. Any other value (usually 0) disables debug reporting.

Field: Report During Warmup

This field allows the debug data to be reported during the warmup period. When a value of 1 is entered the data is reported at all times, even during warmup. Any other value (usually 0) disables “reporting at all time” and debug data is only reported for each environment (RunPeriod or SizingPeriod:DesignDay).

Output:PreprocessorMessage

The Output:PreprocessorMessage object can be used by preprocessor programs to EnergyPlus for passing certain conditions/errors that might not be detected by scripts executing the EnergyPlus system of programs. This allows EnergyPlus to intercept problems and terminate gracefully rather than the user having to track down the exact conditions.

There is no reason for a user to enter an Output:PreprocessorMessage object but you should encourage interface developers to use this feature. More than one Output:PreprocessorMessage objects may be entered. Of course, no preprocessor message objects are necessary if there is no error information to be passed.

Field: Preprocessor Name

The preprocessor name (e.g. EPMacro, ExpandObjects) is entered here. Case is retained so that messages from EnergyPlus look very similar to what a preprocessor would produce.

Field: Error Severity

This is the error severity. If Fatal, EnergyPlus will terminate after showing all preprocessor messages.

Fields: Message Line 1 through Message Line 10

Each line is limited to 100 characters and an appropriate message can be composed.

ZoneCapacitanceMultiplier:ResearchSpecial

This object is an advanced feature that can be used to control the effective storage capacity of the zone. Capacitance multipliers of 1.0 indicate the capacitance is that of the (moist) air in the volume of the specified zone. This multiplier can be increased if the zone air capacitance needs to be increased for stability of the simulation or to allow modeling higher or lower levels of damping of behavior over time. The multipliers are applied to the base value corresponding to the total capacitance for the zone’s volume of air at current zone (moist) conditions.

Field: Sensible Heat Capacity Multiplier

This field is used to alter the effective heat capacitance of the zone air volume. This affects the transient calculations of zone air temperature. Values greater than 1.0 have the effect of smoothing or damping the rate of change in the temperature of zone air from timestep to timestep. Note that sensible heat capacity can also be modeled using internal mass surfaces.

Field: Humidity Capacity Multiplier

This field is used to alter the effective moisture capacitance of the zone air volume. This affects the transient calculations of zone air humidity ratio. Values greater than 1.0 have the effect of smoothing, or damping, the rate of change in the water content of zone air from timestep to timestep.

Field: Carbon Dioxide Capacity Multiplier

This field is used to alter the effective carbon dioxide capacitance of the zone air volume. This affects the transient calculations of zone air carbon dioxide concentration. Values greater than 1.0 have the effect of smoothing or damping the rate of change in the carbon dioxide level of zone air from timestep to timestep.

SimulationControl

The input for SimulationControl allows the user to specify what kind of calculations a given EnergyPlus simulation will perform. For instance the user may want to perform one or more of the sizing calculations but not proceed to an annual weather file simulation. Or the user might have all flow rates and equipment sizes already specified and desire an annual weather without any preceding sizing calculations. Sizing runs, even for large projects, are quickly run – they do not add much to the overall simulation time. The SimulationControl input allows all permutations of run selection by means of 5 yes/no inputs.

Field: Do Zone Sizing Calculation

Input is Yes or No. The default is No. Zone Sizing (see Sizing:Zone object) performs a special calculation, using a theoretical ideal zonal system, and determines the zone design heating and cooling flow rates and loads, saving the results in the zone sizing arrays.

Field: Do System Sizing Calculation

Input is Yes or No. The default is No. System Sizing (see Sizing:System object) also performs a special calculation that, to oversimplify, sums up the results of the zone sizing calculation and saves the results in the system sizing arrays for reporting on component size requirements. Thus, in order to perform the system sizing calculations, the zone sizing arrays need to be filled and hence the zone sizing calculations must be performed in the same run. (This requirement is enforced by the program).

Field: Do Plant Sizing Calculation

Input is Yes or No. The default is No. Unlike Zone and System Sizing, Plant Sizing does not use the Zone or System sizing arrays. Plant Sizing uses the Sizing:Plant object fields and data on the maximum component flow rates. The data on component (such as coil) flow rates is saved and made available to the Plant code whether or not component autosizing is performed and whether or not zone sizing and/or system sizing is performed. Therefore, you can specify Plant Sizing without also specifying to do Zone Sizing or System Sizing calculations.

Field: Run Simulation for Sizing Periods

Input is Yes or No. The default is Yes. Yes implies that the simulation will be run on all the included SizingPeriod objects (i.e., SizingPeriod:DesignDay, SizingPeriod:WeatherFileDays, and SizingPeriod:WeatherFileConditionType). Note that each SizingPeriod object constitutes an “environment” and warmup convergence (see earlier topic under the Building object) will occur for each.

Field: Run Simulation for Weather File Run Periods

Input is Yes or No. The default is Yes. Yes implies the simulation will be run on all the included RunPeriod objects. Note that each RunPeriod object constitutes an “environment” and warmup convergence (see earlier topic under the Building object) will occur for each.

Meter:Custom

A custom meter allows the user to group variables or meters onto a virtual meter that can be used just like a normal meter created by EnergyPlus. For consistency, the items being grouped must all be similar.

Field: Name

This is a user defined name for the custom meter. Names for custom meters cannot duplicate internal meter names.

Field: Fuel Type

A fuel type should be specified for the meter. All assignments to this meter will be checked to assure that the same fuel type is used. Additionally, this may be used in other objects (such as the Demand Limiting). Valid choices for this field are:

Fuel types are generally self-explanatory. Generic is included for convenience when a custom meter is defined that doesn’t quite fit the “fuel” categories. See the examples below.

Field: group(s) Key Name-Report Variable/Meter Name

The rest of the object is filled with parameters of the key name/report variable or meter names. When a meter name is used, the key name field is left blank.

Field: Key Name #

A key name field is used when the following field specifies a report variable. If the field is left blank, then all the report variables in the following field are assigned to the meter.

Field: Report Variable or Meter Name #

Meter:CustomDecrement

The decrement custom meter is very similar to the custom meter specification but additionally allows a predefined meter to be used as the “source” meter and the remaining items subtract from that predefined meter.

Field: Name

This is a user defined name for the custom meter. Names for custom meters cannot duplicate internal meter names.

Field: Fuel Type

Field: Source Meter Name

This name specifies the meter that will be used as the main source for the decrement custom meter. The remainder of the fields are subtracted from the value of this meter to create the meter value named above. The Source Meter is not changed in any way by including this custom meter.

Field: group(s) Key Name-Report Variable/Meter Name

The rest of the object is filled with parameters of the key name/report variable or meter names. When a meter name is used, the key name field is left blank.

Field: Key Name #

A key name field is used when the following field specifies a report variable. If the field is left blank, then all the report variables in the following field are assigned to the meter.

Field: Report Variable or Meter Name #

This field must be a valid report variable name or a valid meter name. Additionally, it must be contained on the Source Meter. Note that, if an error occurs, only the Variable in error will show – confusing things if what was entered was a meter name.

Details of the Meter:Custom/Meter:CustomDecrement are shown on the Meter Details file.

In the following examples, the custom meters are set up to illustrate the capabilities of custom meters. Custom meter “MyGeneralLights” duplicates the InteriorLights:Electricity meter. Custom meter “MyBuildingElectric” duplicates the Electricity:Building meter (by specifying that meter). Custom Meter (Decrement) “MyBuildingOther” uses the Electricity:Building meter as the source meter and subtracts out the values for MyGeneralLights (aka InteriorLights:Electricity). The resultant value for the MyBuildingOther meter should be equal to the value for the meters Electricity:Building – InteriorLights:Electricity.

For an example of “generic” fuel type, one might put the Building Infiltration Heat Loss & Heat Gain on a set of custom meters:

One can then report these values the same way one reports other standard meters.

Simulation Parameter Outputs

These appear in the eplusout.eio file. For details of the reporting, please see the Output Details and Examples document.

Group – Compliance Objects

Not necessarily related directly to simulation, the Compliance Object group provides a repository for a group of objects that can be used directly or indirectly in reporting compliance (such as ASHRAE 90.1) to building standards.

Compliance:Building

The Compliance:Building object describes parameters related to compliance to building standards, building codes, and beyond energy code programs.

Field: Building Rotation for Appendix G

Building Rotation for Appendix G allows for the building model to be rotated for use with compliance such as ASHRAE 90.1 Appendix G. Appendix G requires the building to be rotated 0, 90, 180 and 270 degrees and the values averaged to establish baseline energy use. This input works with relative or world coordinate systems.

Group -- Location – Climate – Weather File Access

Site:Location

The location class describes the parameters for the building’s location. Only one location is allowed. Weather data file location, if it exists, will override any location data in the IDF. Thus, for an annual simulation, a Location does not need to be entered.

Field: Name

Field: Latitude

This field represents the latitude (in degrees) of the facility. By convention, North Latitude is represented as positive; South Latitude as negative. Minutes should be represented in decimal fractions of 60. (15’ is 15/60 or .25)

Field: Longitude

This field represents the longitude (in degrees) of the facility. By convention, East Longitude is represented as positive; West Longitude as negative. Minutes should be represented in decimal fractions of 60. (15’ is 15/60 or .25)

Field: Time Zone

This field represents the time zone of the facility (relative to Greenwich Mean Time or the 0^th meridian). Time zones west of GMT (e.g. North America) are represented as negative; east of GMT as positive. Non-whole hours can be represented in decimal (e.g. 6:30 is 6.5).

Field: Elevation

This field represents the elevation of the facility in meters (relative to sea level).

Units with their abbreviations are shown in Appendix A. And, as shown in an IDF:

Most examples in this document include the comment lines that illustrate each data field’s value. However, this is not necessary (though it makes the IDF more readable). The previous example could also be:

SizingPeriod:DesignDay

The design day input describes the parameters to effect a “design day” simulation, often used for load calculations or sizing equipment. Using the values in these fields, EnergyPlus “creates” a complete days’ worth of weather data (air temperatures, solar radiation, etc.) Normal operation uses the default range multipliers as shown in Figure 6 though users may choose to input their own multiplier schedule. Likewise, normal operation specifies one “humidity indicating condition” which is used to calculate the humidity ratio at maximum temperature – this is used as the constant humidity ratio for the entire day. Again, this can be overridden by specifying a relative humidity schedule or requesting generation of an hourly wet-bulb temperature profile. Multiple design days may be specified.

Field: Name

This field, like the location name, is used simply for reporting and identification. This name must be unique among the SizingPeriod names entered.

Field: Maximum Dry-Bulb Temperature

This numeric field should contain the day’s maximum dry-bulb temperature in degrees Celsius. (Reference Appendix A of this document for EnergyPlus standard units and abbreviations). The MacroDataSets design day files show extreme temperature for locations as indicated in the ASHRAE HOF design condition tables.

Field: Daily Dry-bulb Temperature Range

A design day can have a “high” temperature and a “low” temperature (or can be a constant temperature for each hour of the day). If there is a difference between high and low temperatures, this field should contain the difference from the high to the low. EnergyPlus, by default, distributes this range over the 24 hours in the day as shown in the figure below:

The multipliers are taken from the ASHRAE 2009 HOF. More explicitly, EnergyPlus creates an air temperature for each timestep by using the entered maximum dry-bulb temperature in conjunction with the entered daily range and the above multiplier values. The actual equation used is shown below:

The range multiplier values represent typical conditions of diurnal temperatures (i.e. the low temperature for the day occurring about 5:00 AM and the maximum temperature for the day occurring about 3:00 PM. Note that EnergyPlus does not shift the profile based on the time of solar noon as is optionally allowed in ASHRAE procedures.

ASHRAE research indicates that dry-bulb and wet-bulb temperatures typically follow the same profile, so EnergyPlus can use the default profile to generate humidity conditions (see Humidity Indicating Type = WetBulbProfileDefaultMultipliers below).

Field: Humidity Indicating Conditions at Maximum Dry-Bulb

This numeric field represents the “humidity indicating” conditions that are coincident with the maximum temperature for the day. The value in this field is indicated by the key value in the field Humidity Indicating Type. This numeric value, along with the Maximum Dry-bulb Temperature and Barometric Pressure, is used to determine a humidity ratio and then used to calculate relative humidity, wet-bulb and dewpoint temperatures at each timestep. Note that this field is unnecessary when you put in a humidity indicating day schedule (described later in this section).

Field: Barometric Pressure

This numeric field is the constant barometric pressure (Pascals) for the entire day.

Field: Wind Speed

This numeric field is the wind speed in meters/second (constant throughout the day) for the day. The MacroDataSets design day files includes wind speed values (99.6% - heating, 1% cooling) as indicated in ASHRAE HOF design condition tables. But, you should be aware that traditional values for these are 6.7056 m/s (15 mph) for heating and 3.3528 m/s (7 mph) for cooling. A reminder is shown in the comments for the wind speed values. The comments also note the extreme wind speeds from the ASHRAE tables.

Field: Wind Direction

This numeric field is the source wind direction in degrees. By convention, winds from the North would have a value of 0., from the East a value of 90.

Field: Sky Clearness

This value represents the “clearness” value for the day. This value, along with the solar position as defined by the Location information and the date entered for the design day, help define the solar radiation values for each hour of the day. Traditionally, one uses 0.0 clearness for Winter Design Days.

Field: Rain Indicator

This numeric field indicates whether or not the building surfaces are wet. If the value is 1, then it is assumed that the building surfaces are wet. Wet surfaces may change the conduction of heat through the surface.

Field: Snow Indicator

This numeric field indicates whether or not there is snow on the ground. If the value is 1, then it is assumed there is snow on the ground. Snow on the ground changes the ground reflectance properties.

Field: Day of Month

This numeric field specifies the day of the month. That, in conjunction with the month and location information, determines the current solar position and solar radiation values for each hour of the day.

Field: Month

This numeric field specifies the month. That, in conjunction with the day of the month and location information, determines the current solar position and solar radiation values for each hour of the day.

Field: Day Type

This alpha field specifies the day type for the design day. This value indicates which day profile to use in schedules. For further information, see the Schedule discussion later in this document {Group -- Schedules}. Note that two of the possible day types are SummerDesignDay and WinterDesignDay – allowing the user to customize schedules for the design conditions.

Field: Daylight Saving Time Indicator

This numeric field specifies whether to consider this day to be a Daylight Saving Day. This essentially adds 1 hour to the scheduling times used in items with schedules.

Field: Humidity Indicating Type

Valid choices here are: WetBulb, WetBulbProfileDefaultMultipliers, WetBulbProfileDifferenceSchedule, WetBulbProfileMultiplierSchedule, DewPoint, HumidityRatio, Enthalpy, and Schedule. See just below.

Field: Humidity Indicating Day Schedule Name

Allows specification a day schedule of values for relative humidity or wet-bulb profile per Humidity Indicating Type field. See below.

The Humidity Indicating fields have interacting uses and units, summarized as follows:

These four methods assume constant absolute humidity over the day. Calculate W = humidity ratio at Maximum Dry-Bulb Temperature and Humidity Indicating Conditions. Derive hourly/timestep humidity conditions from W and hour/timestep dry-bulb temperature.

Generate the wet-bulb temperature profile using Default Daily Range Multiplier for Design Days (shown in Figure 6 above) and Daily Wet-Bulb Temperature Range (below). This method is analogous to DefaultMultiplier generation of the dry-bulb temperature profile and is the procedure recommended in Chapter 14 of ASHRAE 2009 HOF.

Generate the wet-bulb profile using multipliers from the Humidity Indicating Day Schedule and Daily Wet-Bulb Temperature Range (below). Analogous to dry-bulb MultiplierSchedule.

Generate the wet-bulb profile by subtracting Humidity Indicating Day Schedule values from the daily maximum wet-bulb temperature (specified in Humidity Indicating Conditions at Maximum Dry-Bulb). Analogous to dry-bulb DifferenceSchedule.

In all cases, the humidity ratio is limited to saturation at the hour/timestep dry-bulb (that is, the dry-bulb temperature is used as specified, but the humidity ratio is modified as needed to be physically possible). Once a valid air state is determined, a complete set of consistent hour/timestep psychrometric values (dewpoint, wet-bulb, and enthalpy) is derived.

Field: Dry-Bulb Temperature Range Modifier Type

If you are happy with lows at 5am and highs at 3pm, you can ignore this field. If you want to specify your own temperature range multipliers (see earlier discussion at the Temperature Range field description), you can specify a type here and create a day schedule which you reference in the next field.

If you specify MultiplierSchedule in this field, then you need to create a day schedule that specifies a multiplier applied to the temperature range field (above) to create the proper dry-bulb temperature range profile for your design day.

If you specify DifferenceSchedule in this field, then you need to create a day schedule that specifies a number to be subtracted from dry-bulb maximum temperature for each timestep in the day. Note that numbers in the delta schedules cannot be negative as that would result in a higher maximum than the maximum previously specified.

If you leave this field blank or enter DefaultMultipliers, then the default multipliers will be used as shown in the “temperature range” field above.

Field: Dry-Bulb Temperature Range Modifier Schedule Name

This field is the name of a day schedule with the values as specified in the Dry-Bulb Temperature Range Modifier Type field above.

Field: Solar Model Indicator

This field allows the user to select ASHRAEClearSky, ASHRAETau, ZhangHuang, or Schedule for solar modeling in the calculation of the solar radiation in the design day. ASHRAEClearSky and ZhangHuang use the Clearness value as part of their calculations. ASHRAETau invokes the revised model specified in Chapter 14 of the ASHRAE 2009 HOF and uses Taub and Taud values (below). Technical details of the models are described in the Engineering Reference. The Schedule choice allows you to enter schedule values for the day’s profile (use the next two fields for the names).

Field: Beam Solar Day Schedule Name

This field allows the option for you to put in your own day profile of beam solar values (wh/m2). These values will replace the calculated values during design day processing.

Field: Diffuse Solar Day Schedule Name

This field allows the option for you to put in your own day profile of diffuse solar values (wh/m2). These values will replace the calculated values during design day processing.

Field: ASHRAE Taub

Optical depth for beam radiation, used only when Solar Model Indicator is ASHRAETau. See next field.

Field: ASHRAE Taud

Optical depth for diffuse radiation, used only when Solar Model Indicator is ASHRAETau. Taub and Taud values are tabulated by month for 5564 locations worldwide on the CD that accompanies the ASHRAE 2009 HOF.

Field: Daily Wet-Bulb Temperature Range

The difference between the maximum and minimum wet-bulb temperatures on the design day (Celsius). Used for generating daily profiles of humidity conditions when Humidity Indicating Type (above) is WetBulbProfileDefaultMultipliers or WetBulbProfileMultiplierSchedule. Values for wet-bulb temperature range are tabulated by month for 5564 locations worldwide on the CD that accompanies the ASHRAE 2009 HOF.

Look at the example files 1ZoneUncontrolled_DDChanges.idf and 1ZoneUncontrolled_DD2009 for several examples of specifying Design Day inputs.

Longer Design Periods

Some features may benefit by using a longer design weather period for sizing or loads calculations. Longer design periods may be created by using the SizingPeriod:WeatherFileDays or SizingPeriod:WeatherFileConditionType objects. These two objects allow for selections from an attached weather file to be used in the sizing calculations.

SizingPeriod:WeatherFileDays

The SizingPeriod:WeatherFileDays object describes using a selected period from the “attached” weather file to be used in load calculations or sizing equipment. The period selected can be as small as a single day or larger. Multiple periods may be input.

Field: Name

This field allows for an assigned name for this run period so it can be tracked easily in sizing and other outputs.

Field: Begin Month

This numeric field should contain the starting month number (1=January, 2=February, etc.) for the annual run period desired.

Field: Begin Day of Month

This numeric field should contain the starting day of the starting month (must be valid for month) for the annual run period desired.

Field: End Month

This numeric field should contain the ending month number (1=January, 2=February, etc.) for the annual run period desired.

Field: End Day of Month

This numeric field should contain the ending day of the ending month (must be valid for month) for the annual run period desired.

Field: Day of Week for Start Day

For flexibility, the day of week indicated on the weather file can be overridden by this field’s value. Valid days of the week (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday) or special days (SummerDesignDay, WinterDesignDay, CustomDay1, CustomDay2) must be entered in this field. To clarify, this value will be used as the Start Day (type) for this sizing period. When weekdays are used, each subsequent day in the period will be incremented. When SummerDesignDay, WinterDesignDay, CustomDay1, CustomDay2 – are used, the day type will be applied for the entire period.

Field: Use Weather File Daylight Saving Period

Weather files can contain indicators of Daylight Saving Period days. For flexibility, you may want to ignore these designations on the weather file. This field should contain the word Yes if you will accept daylight saving period days as contained on the weather file (note: not all weather files may actually have this period) or No if you wish to ignore Daylight Saving Period days that may be on the weather file.

Field: Use Weather File Rain and Snow Indicators

Weather files can contain “rain” and “snow” indicators. (EPW field “Present Weather Codes” – described in the AuxiliaryPrograms document). In turn, rain indicates wet surfaces which changes the film convection coefficient for the surface. Other models may use rain as well (Ground Heat Exchangers). Snow indicators can change the ground reflectance if there is snow on the ground. Entering “Yes” in this field allows the weather file conditions to represent “Rain” and “Snow”; entering “No” in the field “turns off” the rain/snow indicators for this period. You might use this to be able to compare two “same location” weather files of different years, origins, etc.

SizingPeriod:WeatherFileConditionType

When the EPW files are created, a heuristic procedure identifies extreme and typical periods in the actual weather file. This object will allow one of those periods to be selected for sizing or load calculations (typically). Multiple objects may be input.

Field: Name

This field allows for an assigned name for this run period so it can be tracked easily in sizing and other outputs.

Field: Period Selection

This field allows the generic period calculated from the weather file to be selected for this run period. It is not completely generic as there may be extreme cold periods in some weather files but extreme wet periods (tropical) in others. Not all weather files have all of the valid choices. The choices for this field are:

Field: Day of Week for Start Day

Field: Use Weather File Daylight Saving Period

Field: Use Weather File Rain and Snow Indicators

RunPeriod

The RunPeriod object describes the elements necessary to create a weather file simulation. Multiple run periods may be input. EnergyPlus accepts weather files in the special EnergyPlus weather format (described below in this document). These files can describe Daylight Saving Time periods as well as holidays within their definitions. The RunPeriod object allows the user to override the use of both the Daylight Saving Period (i.e. use or ignore) and holidays that are embedded within the weather file. Note that the weather file also may contain design condition information, typical and extreme period information, ground temperatures based on air temperature calculations.

Field: Name

This optional field allows the RunPeriod to be named for output reporting. When left blank, the weather file location name is used.

Field: Begin Month

This numeric field should contain the starting month number (1=January, 2=February, etc.) for the annual run period desired.

Field: Begin Day of Month

This numeric field should contain the starting day of the starting month (must be valid for month) for the annual run period desired.

Field: End Month

This numeric field should contain the ending month number (1=January, 2=February, etc.) for the annual run period desired.

Field: End Day of Month

This numeric field should contain the ending day of the ending month (must be valid for month) for the annual run period desired.

Field: Day of Week for Start Day

For flexibility, the day of week indicated on the weather file can be overridden by this field’s value. Valid days of the week (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday) must be entered in this field. To clarify, this value will be used as the Start Day (type) for this run period and subsequent days will be implemented. If a blank or UseWeatherFile is entered here, then the starting day type will be calculated from the weather file (ref: Auxiliary Programs document about Data Periods).

Field: Use Weather File Holidays and Special Days

Weather files can contain holiday designations or other kinds of special days. These day types cause a corresponding day’s schedule (see SCHEDULE definitions below) to be used during that day. This field should contain the word Yes if holidays or other special days indicated directly on the weather file should retain their “day type” or No if holidays or other special days on the weather file should be ignored. Reference the RunPeriodControl:SpecialDays object below to enter your own special days and holidays.

Field: Use Weather File Daylight Saving Period

Weather files can contain indicators of Daylight Saving period days. For flexibility, you may want to ignore these designations on the weather file. This field should contain the word Yes if you will accept daylight saving period days as contained on the weather file (note: not all weather files may actually have this period) or No if you wish to ignore Daylight Saving period days that may be on the weather file.

Field: Apply Weekend Holiday Rule

In some countries (notably the US), when holidays fall on weekends, they are often observed on a weekday close to the holiday day. (Usually if the specific day falls on a Saturday, the observed day is Friday; if on a Sunday, the observed day is Monday). EnergyPlus will represent this custom using the value in this field. If the field is Yes, then specific date holidays that have a duration of one day, will be “observed” on the Monday after the day. (Specific day holidays are such as January 1 – a day-month combination). If the field is blank or No, then the holiday will be shown on the day-month as entered. As this option is listed at the RunPeriod, all applicable special days for the run will use the rule – there is no override for individual special days.

Field: Use Weather File Rain Indicators

Weather files can contain “rain” indicators. (EPW field “Present Weather Codes” – described in the AuxiliaryPrograms document). In turn, rain indicates wet surfaces which changes the film convection coefficient for the surface. Other models may use rain as well (Ground Heat Exchangers). Entering “Yes” in this field allows the weather file conditions to represent “Rain”; entering “No” in the field “turns off” the rain indicator for this period. You might use this to be able to compare two “same location” weather files of different years, origins, etc.

Field: Use Weather File Snow Indicators

Weather files can contain “snow” indicators. (EPW field “Snow Depth” > 0 indicates “Snow on the ground”). In turn, snow changes the reflectivity of the ground and cascades changes of this reflectivity. Entering “Yes” in this field allows the weather file conditions to represent “Snow”; entering “No” in the field “turns off” the snow indicator for this period. You might use this to be able to compare two “same location” weather files of different years, origins, etc.

Field: Number of Times Runperiod to be Repeated

This numeric field represents the number of times (usually years) the simulation has to be carried out in a multi runperiod simulation. The default value is set to 1. The number of years of simulation, in case of a Ground Loop Heat Exchanger (GLHE) simulation, should be equal to the length of simulation field in GLHE object. Note that you can specify a number of simulation years with a shorter run period (e.g. 1 week) and EnergyPlus will repeat the simulation of the shorter run period for that many times.

RunPeriodControl:SpecialDays

For weather file run periods, special day run periods can be described. These will always be in effect for the selected days in the run period. Depending on the Use Special Days value in the RunPeriod object, these can augment any special days included on the weather file.

Field: Name

This alpha field is the title for the special day period. It must be unique among all the special day period objects entered.

Field: Start Date

This field is the starting date for the special day period. Dates in this field can be entered in several ways as shown in the accompanying table:

In the table, Month can be one of (January, February, March, April, May, June, July, August, September, October, November, December). Abbreviations of the first three characters are also valid.

In the table, Weekday can be one of (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday). Abbreviations of the first three characters are also valid.

Field: Duration

This numeric field specifies how long (number of days) the special day period lasts.

Field: Special Day Type

This alpha field designates the “day type” for schedule use during the special period. It must be one of (Holiday, SummerDesignDay, WinterDesignDay, CustomDay1, CustomDay2).

RunPeriodControl-DaylightSavingTime

Similar to a special day period, a daylight saving period may be entered to be applied to weather file run periods. These will always be in effect, regardless of the value entered on the RunPeriod object. Note that this period will always override any daylight saving period specified in a weather file.

Field: Start Date

This is the starting date of the daylight saving period. Note that it can be entered in several formats as shown in Table 3. Date Field Interpretation.

Field: End Date

This is the ending date of the daylight saving period. Note that it can be entered in several formats as shown in Table 3. Date Field Interpretation.

Of course, these could not all appear in the same IDF as only one DaylightSavingPeriod object per input file is allowed. More information on Daylight Saving Periods can be seen on the web at: http://www.webexhibits.org/daylightsaving/ The ASHRAE Handbook of Fundamentals [ASHRAE 2005] also contains information about daylight saving periods and their climatic information now includes start and end dates for many locations.

WeatherProperty:SkyTemperature

Sky Temperature, or radiative sky temperature, is internally calculated by EnergyPlus using an algorithm using horizontal infrared radiation from sky, cloudiness factors and current temperaure. The algorithm is fully described in the Engineering Reference document. For flexibility, the following object can be entered to override the internal calculations. Much of the literature describes the sky temperature as relative to either drybulb or dewpoint temperature.

Field: Name

This name references an existing design period (i.e., SizingPeriod:DesignDay, SizingPeriod:WeatherFileDays, or SizingPeriod:WeatherFileConditionType) or run period (by name or blank for all run periods).

Field: Calculation Type

Allowable entries here are: ScheduleValue, DifferenceScheduleDryBulbValue, or DifferenceScheduleDewPointValue. In each case the following field must specify a valid schedule name. ScheduleValue – the values in the schedule are used as the sky temperature. DifferenceScheduleDryBulbValue – the values in the schedule are used as a difference to the drybulb temperature value (+values would then be greater than the drybulb temperature, -values would then be less than the drybulb temperature) for the resulting sky temperature value. DifferenceScheduleDewPointValue – the values in the schedule are used as a difference to the dewpoint temperature value (+values would then be greater than the dewpoint temperature, -values would then be less than the dewpoint temperature) for the resulting sky temperature value.

Field: ScheduleName

This field specifies a schedule name to accomplish the sky temperature calculation from the previous field. A Schedule:Day:* (i.e., Schedule:Day:Hourly, Schedule:Day:Interval, Schedule:Day:List) should be specified if the name in the name field matches a SizingPeriod:DesignDay object. If the name is one of the weather file period specifications (i.e. matches a SizingPeriod:WeatherFileDays, SizingPeriod:WeatherFileConditionType or RunPeriod), then the schedule name must match a full year schedule (i.e. Schedule:Year, Schedule:Compact, Schedule:File, or Schedule:Constant).

Site:WeatherStation

The Site:WeatherStation object is used to specify the measurement conditions for the climatic data listed in the weather file. These conditions indicate the height above ground of the air temperature sensor, the height above ground of the wind speed sensor, as well as coefficients that describe the wind speed profile due to the terrain surrounding the weather station. There are necessary correlations between the entries for this object and some entries in the Building object, specifically the Terrain field.

Weather stations throughout the world (ref: WMO – World Meteorological Organization) take their measurements at standard conditions:

§ Weather station is in a flat, open field with little protection from the wind.

When using weather data from standard sources (e.g., TMY2, IWEC, TMY, or ASHRAE design day data), it is not necessary to use the Site:WeatherStation object. However, if you are using custom weather data or real-time weather data, you may need to read and understand the concepts in the Site:WeatherStation object.

The measurement conditions at the weather station (i.e., the weather file) are used by EnergyPlus in conjunction with the Terrain field of the Building object, or optionally with the Site:HeightVariation object (see below), to calculate the local variation in atmospheric properties as a function of height above ground. Outdoor air temperature decreases with height, while wind speed increases with height. The algorithms for this calculation are in the Engineering Reference.

The Site:WeatherStation object is useful when working with a custom weather file that includes data that were not measured at the WMO standard conditions. For example, the weather data could be measured on site, or on the roof top of a nearby building. The wind speed profile coefficients can be estimated from the table below or calculated beforehand using more sophisticated techniques such as CFD modeling of the weather station terrain.

If the Site:WeatherStation object is omitted from the input file, the WMO standard measurement conditions are assumed.

Field: Wind Sensor Height Above Ground

Field: Wind Speed Profile Exponent

The wind speed profile exponent for the terrain surrounding the weather station. The exponent can be estimated from the table above or calculated beforehand using more sophisticated techniques, such as CFD modeling of the weather station terrain.

Field: Wind Speed Profile Boundary Layer Thickness

The wind speed profile boundary layer thickness [m] for the terrain surrounding the weather station. The boundary layer can be estimated from the table above or calculated beforehand using more sophisticated techniques, such as CFD modeling of the weather station terrain.

Field: Air Temperature Sensor Height Above Ground

For example, if you are using weather data measured on the top of your building, you should set the Wind Sensor Height Above Ground and the Air Temperature Sensor Height Above Ground to equal the height of your building (say 30 m). The Wind Speed Profile Exponent and Wind Speed Profile Boundary Layer Thickness should be set to match the values associated with the Terrain field of the Building object, or the equivalent fields of the Site:HeightVariation object.

This would change if you had a different wind speed profile exponent or wind speed profile boundary layer thickness at your site.

Site:HeightVariation

The Site:HeightVariation object is used to specify the local variation in atmospheric properties at the site and should be used only if you require advanced control over the height-dependent variations for wind speed and temperature. The coefficients set by this object are used by EnergyPlus, in conjunction with the Site:WeatherStation object (see above), to calculate the local variation in atmospheric properties as a function of height above ground. Outdoor air temperature decreases with height, while wind speed increases with height. The local outdoor air temperature and wind speed are calculated separately for all zones and surfaces, and optionally for outdoor air nodes for which a height has been specified (see OutdoorAir:Node object). With the default inputs, wind speed falls significantly at heights lower than the weather station measurement height, and temperature increases slightly. The algorithms for this calculation are in the Engineering Reference. There are necessary correlations between the entries for this object and some entries in the Building object, specifically the Terrain field.

Note that using this object overrides the wind speed profile coefficients implied by the Terrain field of the Building object even if the wind speed profile fields are left blank. The wind speed profile coefficients can be estimated from the table above (see Site:WeatherStation) or calculated beforehand using more sophisticated techniques such as CFD modeling of the site terrain.

Field: Wind Speed Profile Exponent

The wind speed profile exponent for the terrain surrounding the site. The exponent can be estimated from the table above (see Site:WeatherStation) or calculated beforehand using more sophisticated techniques, such as CFD modeling of the site terrain. Note that using this object overrides the wind speed profile coefficients implied by the Terrain field of the Building object even if this field is left blank.

Field: Wind Speed Profile Boundary Layer Thickness

The wind speed profile boundary layer thickness [m] for the terrain surrounding the site. The boundary layer can be estimated from the table above (see Site:WeatherStation) or calculated beforehand using more sophisticated techniques, such as CFD modeling of the site terrain. Note that using this object overrides the wind speed profile coefficients implied by the Terrain field of the Building object even if this field is left blank. This field can be set to zero to turn off all wind dependence on height.

Field: Air Temperature Gradient Coefficient

The air temperature gradient coefficient [K/m] is a research option that allows the user to control the variation in outdoor air temperature as a function of height above ground. The real physical value is 0.0065 K/m. This field can be set to zero to turn off all temperature dependence on height. Note that the Air Temperature Sensor Height in the Site:WeatherStation object should also be set to zero in order to force the local outdoor air temperatures to match the weather file outdoor air temperature. This change is required because the Site:WeatherStation object assumes an air temperature gradient of 0.0065 K/m.

Site:GroundTemperature:BuildingSurface

Ground temperatures are used for the ground heat transfer model. There can be only one ground temperature object included, and it is used as the outside surface temperature for all surfaces with Outside Boundary Condition=Ground. The object is options if you have no surfaces with ground contact. The outside surface temperature for individual surfaces can be specified using the OtherSideCoefficients (ref: SurfaceProperty:OtherSideCoefficients) object that allows Toutside to be set with a schedule. This permits using any number of different outside face temperatures in addition to the ground temperature.

More information about determining appropriate ground temperatures is given in the Auxiliary Programs document.

Field: Month Temperature(s) – 12 fields in all

Each numeric field is the monthly ground temperature (degrees Celsius) used for the indicated month (January=1^st field, February=2^nd field, etc.)

Site:GroundTemperature:Shallow

Site:GroundTemperature:Shallow are used by the Surface Ground Heat Exchanger (i.e. object: GroundHeatExchanger:Surface). Only one shallow ground temperature object can be included.

Field: Month Temperature(s) – 12 fields in all

Each numeric field is the monthly surface ground temperature (degrees Celsius) used for the indicated month (January=1^st field, February=2^nd field, etc.)

Site:GroundTemperature:Deep

Site:GroundTemperature:Deep are used by the Pond Ground Heat Exchanger and Vertical Ground Heat Exchanger objects (i.e. objects: GroundHeatExchanger:Pond and GroundHeatExchanger:Vertical). Only one deep ground temperature object can be included.

Field: Month Temperature(s) – 12 fields in all

Each numeric field is the monthly deep ground temperature (degrees Celsius) used for the indicated month (January=1^st field, February=2^nd field, etc.)

Site:GroundTemperature:FCfactorMethod

Site:GroundTemperature:FCfactorMethod is used only by the underground walls or slabs-on-grade or underground floors defined with C-factor (Construction:CfactorUndergroundWall) and F-factor (Construction:FfactorGroundFloor) method for code compliance calculations where detailed construction layers are unknown. Only one such ground temperature object can be included. The monthly ground temperatures for this object are close to the monthly outside air temperatures delayed by three months. If user does not input this object in the IDF file, it will be defaulted to the 0.5m set of monthly ground temperatures from the weather file if they are available. Entering these will also overwrite any ground temperatures from the weather file in the F and C factor usage. If neither is available, an error will result.

Field: Month Temperature(s) – 12 fields in all

Each numeric field is the monthly ground temperature (degrees Celsius) used for the indicated month (January=1^st field, February=2^nd field, etc.)

Site:GroundReflectance

Ground reflectance values are used to calculate the ground reflected solar amount. This fractional amount (entered monthly) is used in this equation:

Of course, the Ground Reflected Solar is never allowed to be negative. The ground reflectance can be further modified when snow is on the ground by the Snow Ground Reflectance Modifier. To use no ground reflected solar in your simulation, enter 0.0 for each month.

Field: Month Average Ground Reflectance(s) – 12 fields in all

Each numeric field is the monthly average reflectivity of the ground used for the indicated month (January=1^st field, February=2^nd field, etc.)

Site:GroundReflectance:SnowModifier

It is generally accepted that snow resident on the ground increases the basic ground reflectance. EnergyPlus allows the user control over the snow ground reflectance for both “normal ground reflected solar” calculations (see above) and snow ground reflected solar modified for daylighting. These are entered under this object and both default to 1 (same as normal ground reflectance – no special case for snow which is a conservative approach).

Field: Ground Reflected Solar Modifier

This field is a decimal number which is used to modified the basic monthly ground reflectance when snow is on the ground (from design day input or weather data values).

Field: Daylighting Ground Reflected Solar Modifier

This field is a decimal number which is used to modified the basic monthly ground reflectance when snow is on the ground (from design day input or weather data values).

Outputs will show both the inputs from the above object as well as monthly values for both Snow Ground Reflectance and Snow Ground Reflectance for Daylighting.

Site:WaterMainsTemperature

The Site:WaterMainsTemperature object is used to calculate water temperatures delivered by underground water main pipes. The mains temperatures are used as default, make-up water temperature inputs for several plant objects, including: WaterUse:Equipment, WaterUse:Connections, WaterHeater:Mixed and WaterHeater:Stratified. The mains temperatures are also used in the water systems objects to model the temperature of cold water supplies.

Water mains temperatures are a function of outdoor climate conditions and vary with time of year. A correlation has been formulated to predict water mains temperatures based on two weather inputs:

These values can be easily calculated from annual weather data using a spreadsheet or from the ".stat" file available with the EnergyPlus weather files at www.energyplus.gov. Monthly statistics for dry-bulb temperatures are shown with daily averages. The daily averages are averaged to obtain the annual average. The maximum and minimum daily average are subtracted to obtain the maximum difference. For more information on the water mains temperatures correlation, see the EnergyPlus Engineering Document.

Alternatively, the Site:WaterMainsTemperature object can read values from a schedule. This is useful for measured data or when water comes from a source other than buried pipes, e.g., a river or lake.

If there is no Site:WaterMainsTemperature object in the input file, a default constant value of 10 C is assumed.

Field: Calculation Method

This field selects the calculation method and must have the keyword Schedule or Correlation.

Field: Schedule Name

If the calculation method is Schedule, the water mains temperatures are read from the schedule referenced by this field. If the calculation method is Correlation, this field is ignored.

Field: Annual Average Outdoor Air Temperature

If the calculation method is Correlation, this field is used in the calculation as the annual average outdoor air temperature (dry-bulb) [C]. If the calculation method is Schedule, this field is ignored.

Field: Maximum Difference In Monthly Average Outdoor Air Temperatures

If the calculation method is Correlation, this field is used in the calculation as the maximum difference in monthly average outdoor air temperatures [∆C]. If the calculation method is Schedule, this field is ignored.

Site:Precipitation

The Site:Precipitation object is used to describe the amount of water precipitation at the building site over the course of the simulation run period. Precipitaition includes both rain and the equivalent water content of snow. Precipitation is not yet described well enough in the usual building weather data file. So this object is used to provide the data using Schedule objects that define rates of precipitation in meters per hour.

A set of schedules for site precipitation have been developed for USA weather locations and are provided with EnergyPlus in the data set called PrecipitationSchedulesUSA.idf. The user can develop schedules however they want. The schedules in the data set were developed using EnergyPlus’ weather file (EPW) observations and the average monthly precipitation for the closest weather site provided by NOAA. EPW files for the USA that were based on TMY or TMY2 include weather observations for Light/Moderate/Heavy rainfall, however most international locations do not include these observations. The values were modeled by taking the middle of the ranges quoted in the EPW data dictionary. The assumed piecewise function is shown below.

The values were inserted on hour by hour basis for the month based on the observations. Then each month was rescaled to meet the average precipitation for the month based on the 30-year average (1971-2000) provided by the NOAA/NCDC. Therefore, the flags in the EPW file match the precipitation schedules for the USA. Note that summing the average monthly precipitation values will not give you the average yearly precipitiation. The resulting value may be lower or higher than the average yearly value.

Once the typical rainfall pattern and rates are scheduled, the Site Precipitation object provides a method of shifting the total rainfall up or down for design purposes. Wetter or drier conditions can be modeled by changing the Design Annual Precipitation although the timing of precipitation throughout the year will not be changed.

Field: Precipitation Model Type

Choose rainfall modeling options. Only available option is ScheduleAndDesignLevel.

Field: Design Level for Total Annual Precipitation

Magnitude of total precipitation for an annual period to be used in the model. Value selected by the user to correspond with the amount of precipitation expected or being assumed for design purposes. The units are in meters. This field works with the following two fields to allow easily shifting the amounts without having to generate new schedules.

Field: Precipitation Rate Schedule Name

Name of a schedule defined elsewhere that describes the rate of precipitation. The precipitation rate schedule is analogous to weather file data. However, weather files for building simulation do not currently contain adequate data for such calculations. Therefore, EnergyPlus schedules are used to enter the pattern of precipitation events. The values in this schedule are the average rate of precipitation in meters per hour. The integration of these values over an annual schedule should equal the nominal annual precipitation.

Field: Average Total Annual Precipitation

Magnitude of annual precipitation associated with the rate schedule. This value is used to normalize the precipitation.

RoofIrrigation

The RoofIrrigation object is used to describe the amount of irrigation on the ecoroof surface over the course of the simulation runperiod. This object is used to provide irrigation data using Schedule objects that define rates of irrigation in meters per hour. These schedules can be one of two types: Schedule, or SmartSchedule. The Schedule type is used to force an irrigation schedule regardless of the current moisture state of the soil. The SmartSchedule type allows the precipitation schedule to be overridden if the current moisture state of the soil is greater than 30% saturated.

Field: Irrigation Model Type

Choose irrigation modeling options. Available options are Schedule and SmartSchedule.

Field: Irrigation Rate Schedule Name

Name of a schedule defined elsewhere that describes the rate of irrigation. The values in this schedule are the average rate of irrigation in meters per hour.

Climate Group Outputs

Climate related variables appear in two places for EnergyPlus outputs. Certain objects that are invariant throughout a simulation period have lines appear in the eplusout.eio file. For descriptions of this reporting, please see the Output Details and Examples document.

Weather Data Related Outputs

Variables related to ambient environment data are available at timestep and higher resolutions. Below is a variable dictionary of these variables and subsequent definitions:

Outdoor Dry Bulb [C]

Outdoor Dew Point [C]

Outdoor Wet Bulb [C]

The outdoor wet-bulb temperature is derived (at the timestep) from the values for dry-bulb temperature, humidity ratio and barometric pressure.

Outdoor Humidity Ratio [kgWater/kgAir]

The outdoor humidity ratio is derived (at the timestep) from the dry-bulb temperature, relative humidity and barometric pressure.

Outdoor Relative Humidity [%]

Outdoor Barometric Pressure [Pa]

Wind Speed [m/s]

Wind Direction [degree]

Sky Temperature [C]

The sky temperature is derived from horizontal infrared radiation intensity. It is expressed in degrees C. The default calculation is shown below but this value may be modified by the WeatherProperty:SkyTemperature object. Note that Sigma is the Stefan-Boltzmann constant in the following equation:

Horizontal Infrared Radiation Intensity [W/m2]

The horizontal infrared radiation intensity is expressed in W/m² based, if missing from the weather file, on opaque sky cover, sky emissivity, temperature and other factors. The general calculation of Horizontal Infrared Radiation Intensity is discussed in both the Engineering Reference and the Auxiliary Programs document.

Diffuse Solar [W/m2]

Diffuse solar is the amount of solar radiation in W/m² received from the sky (excluding the

Direct Solar [W/m2]

Direct solar is amount of solar radiation in W/m² received within a 5.7° field of view centered on the sun. This is also known as Beam Solar.

Liquid Precipitation [mm]

This is the amount of liquid precipitation (mm). The source of this field may be the weather file or the Site:Precipitation object.

Ground Reflected Solar [W/m2]

The ground reflected solar amount (W/m²) is derived from the Beam Solar, Diffuse Solar, User specified Ground Reflectance (for month) and Solar Altitude Angle:

Ground Temperature [C]

The ground temperature is reported in degrees C – this is a user-specified input by month.

Surface Ground Temperature [C]

The ground temperature is reported in degrees C – this is a user-specified input (object: Site:GroundTemperature:Shallow) by month.

Deep Ground Temperature [C]

The ground temperature is reported in degrees C – this is a user-specified input (object: Site:GroundTemperature:Deep) by month.

FCFactor Ground Temperature [C]

The FCFactor ground temperature is reported in degrees C – this is a user-specified input (object: Site:GroundTemperature:FCfactorMethod) by month or gleaned from the weather file as noted in the description of the object.

Outdoor Enthalpy [J/kg]

Outdoor enthalpy is derived at each timestep from the Outdoor Dry-bulb and the Outdoor Humidity Ratio. It is reported in J/kg.

Outdoor Air Density [kg/m3]

Outdoor air density is derived at each timestep from the Outdoor Barometric Pressure, the Outdoor Dry-bulb temperature and the Outdoor Humidity Ratio. It is reported in units kg/m³.

Solar Azimuth Angle [degree]

The Solar Azimuth Angle (f) is measured from the North (clockwise) and is expressed in degrees. This is shown more clearly in the following figure.

Solar Altitude Angle [degree]

The Solar Altitude Angle (b) is the angle of the sun above the horizontal (degrees).

Solar Hour Angle [degree]

The Solar Hour Angle (H) gives the apparent solar time for the current time period (degrees). It is common astronomical practice to express the hour angle in hours, minutes and seconds of time rather than in degrees. You can convert the hour angle displayed from EnergyPlus to time by dividing by 15. (Note that 1 hour is equivalent to 15 degrees; 360° of the Earth’s rotation takes place every 24 hours.) The relationship of angles in degrees to time is shown in the following table:

Fraction of Time Raining

This field shows whether or not (1=yes, 0=no) the weather shows “raining”. For a Design Day, one can denote rain for the entire day but not timestep by timestep. Weather files may indicate rain for a single time interval. This is an “averaged” field – thus a 1 shown for a time period (e.g. daily reporting) means that it was raining during each timestep of that period.

Fraction of Time Snow On Ground

This field shows whether or not (1=yes, 0=no) the weather shows “snow on the ground”. For a Design Day, one can denote snow for the entire day but not timestep by timestep. Weather files may indicate snow (snow depth) for a single time interval. This is an “averaged” field – thus a 1 shown for a time period (e.g. daily reporting) means that there was snow on the ground during each timestep of that period.

Daylight Saving Time Indicator

This field shows when daylight saving time (1=yes, 0=no) is in effect. Though shown as an average variable, this value is only set on a daily basis.

DayType Index

This field shows what “day type” the current day is. Daytypes are (1=Sunday, 2=Monday, etc.) with Holiday=8, SummerDesignDay=9, WinterDesignDay=10, CustomDay1=11, CustomDay2=12. Though shown as an average variable, this value is only set on a daily basis.

Water Mains Temperature

The value of the Water Mains Temperature is reported in C following the calculation shown in the Water Mains Temperature object.

Site Precipitation Rate [m/s]

Site Precipitation [m]

The rate and quantity of precipitation at the site. These outputs are only available if a Site Precipication object is used. Precipitation is measured in meters.

Roof Irrigation Scheduled Amount[m]

This is the scheduled amount of irrigation for the green roof (ecoroof) based on the user input. Amount is measured in meters.

Roof Irrigation Actual Amount[m]

This is the actual amount of irrigation for the green roof (ecoroof) based on the scheduled user input and moisture state/saturation of the soil. Amount is measured in meters.

Outputs for local temperature/wind speed calculations

Local atmospheric properties for outdoor air temperature and wind speed are separately calculated and reported for all zones, surfaces, and outdoor air nodes. The report variables are associated with their respective objects:

Zone Outdoor Dry Bulb [C]

The outdoor air dry-bulb temperature calculated at the height above ground of the zone centroid.

Zone Outdoor Wet Bulb [C]

The outdoor air wet-bulb temperature calculated at the height above ground of the zone centroid.

Zone Outdoor Wind Speed [m/s]

The outdoor wind speed calculated at the height above ground of the zone centroid.

Surface Ext Outdoor Dry Bulb [C]

The outdoor air dry-bulb temperature calculated at the height above ground of the surface centroid.

Surface Ext Outdoor Wet Bulb [C]

The outdoor air wet-bulb temperature calculated at the height above ground of the surface centroid.

Surface Ext Wind Speed [m/s]

The outdoor wind speed calculated at the height above ground of the surface centroid.

System Node Temp [C]

When reporting for the OutdoorAir:Node object, this is the outdoor air dry-bulb temperature calculated at the height above ground of the node, if height is specified in the input.

Group -- Schedules

This group of objects allows the user to influence scheduling of many items (such as occupancy density, lighting, thermostatic controls, occupancy activity). In addition, schedules are used to control shading element density on the building.

EnergyPlus schedules consist of three pieces: a day description, a week description, and an annual description. An optional element is the schedule type. Each description level builds off the previous sub-level. The day description is simply a name and the values that span the 24 hours in a day to be associated with that name. The week description also has an identifier (name) and twelve additional names corresponding to previously defined day descriptions. There are names for each individual day of the week plus holiday, summer design day, winter design day and two more custom day designations. Finally, the annual schedule contains an identifier and the names and FROM-THROUGH dates of the week schedules associate with this annual schedule. The annual schedule can have several FROM-THROUGH date pairs. One type of schedule reads the values from an external file to facilitate the incorporation of monitored data or factors that change throughout the year.

Schedules are processed by the EnergyPlus Schedule Manager, stored within the Schedule Manager and are accessed through module routines to get the basic values (timestep, hourly, etc). Values are resolved at the Zone Timestep frequency and carry through any HVAC timesteps.

Day Type

A brief description of “Day Type” which is used in the SizingPeriod objects, RunPeriodControl:SpecialDays object, the Sizing objects and also used by reference in the Schedule:Week:Daily object (discussed later in this section).

Schedules work on days of the week as well as certain specially designated days. Days of the week are the normal – Sunday, Monday, Tuesday, Wednesday, Thursday, Friday and Saturday. Special day types that can be designated are: Holiday, SummerDesignDay, WinterDesignDay, CustomDay1, CustomDay2. These day types can be used at the user’s convenience to designate special scheduling (e.g. lights, electric equipment, set point temperatures) using these days as reference.

For example, a normal office building may have normal “occupancy” rules during the weekdays but significantly different use on weekend. For this, you would set up rules/schedules based on the weekdays (Monday through Friday, in the US) and different rules/schedules for the weekend (Saturday and Sunday, in the US). However, you could also specially designate SummerDesignDay and WinterDesignDay schedules for sizing calculations. These schedules can be activated by setting the Day Type field in the Design Day object to the appropriate season (SummerDesignDay for cooling design calculations; WinterDesignDay for heating design calculations).

In a different building, such as a theater/playhouse, the building may only have occupancy during certain weeks of the year and/or certain hours of certain days. If it was every week, you could designate the appropriate values during the “regular” days (Sunday through Saturday). But this would also be an ideal application for the “CustomDay1” and/or “CustomDay2”. Here you would set the significant occupancy, lighting, and other schedules for the custom days and use unoccupied values for the normal weekdays. Then, using a weather file and setting special day periods as appropriate, you will get the “picture” of the building usage during the appropriate periods.

ScheduleTypeLimits

Schedule types can be used to validate portions of the other schedules. Hourly day schedules, for example, are validated by range -- minimum/maximum (if entered) -- as well as numeric type (continuous or discrete). Annual schedules, on the other hand, are only validated for range – as the numeric type validation has already been done.

Field: Name

This alpha field should contain a unique (within the schedule types) designator. It is referenced wherever Schedule Type Limits Names can be referenced.

Field: Lower Limit Value

In this field, the lower (minimum) limit value for the schedule type should be entered. If this field is left blank, then the schedule type is not limited to a minimum/maximum value range.

Field: Upper Limit Value

In this field, the upper (maximum) limit value for the schedule type should be entered. If this field is left blank, then the schedule type is not limited to a minimum/maximum value range.

Field: Numeric Type

This field designates how the range values are validated. Using Continuous in this field allows for all numbers, including fractional amounts, within the range to be valid. Using Discrete in this field allows only integer values between the minimum and maximum range values to be valid.

Field: Unit Type

This field is used to indicate the kind of units that may be associated with the schedule that references the ScheduleTypeLimits object. It is used by IDF Editor to display the appropriate SI and IP units. This field is not used by EnergyPlus. The available options are shown below. If none of these options are appropriate, select Dimensionless.

Day Schedules

The day schedules perform the assignment of pieces of information across a 24 hour day. This can occur in various fashions including a 1-per hour assignment, a user specified interval scheme or a list of values that represent an hour or portion of an hour.

Schedule:Day:Hourly

The Schedule:Day:Hourly contains an hour-by-hour profile for a single simulation day.

Field: Name

This field should contain a unique (within all DaySchedules) designation for this schedule. It is referenced by WeekSchedules to define the appropriate schedule values.

Field: Schedule Type Limits Name

This field contains a reference to the Schedule Type Limits object. If found in a list of Schedule Type Limits (see above), then the restrictions from the referenced object will be used to validate the hourly field values (below).

Field: Hour Values (1-24)

These fields contain the hourly values for each of the 24 hours in a day. (Hour field 1 represents clock time 00:00:01 AM to 1:00:00 AM, hour field 2 is 1:00:01 AM to 2:00:00 AM, etc.) The values in these fields will be passed to the simulation as indicated for “scheduled” items.

Schedule:Day:Interval

The Schedule:Day:Interval introduces a slightly different way of entering the schedule values for a day. Using the intervals, you can shorten the “hourly” input of the “Schedule:Day:Hourly” object to 2 fields. And, more importantly, you can enter an interval that represents only a portion of an hour. Schedule values are “given” to the simulation at the zone timestep, so there is also a possibility of “interpolation” from the entries used in this object to the value used in the simulation.

Field: Name

This field should contain a unique (within all DaySchedules) designation for this schedule. It is referenced by WeekSchedules to define the appropriate schedule values.

Field: Schedule Type Limits Name

Field: Interpolate to Timestep

The value contained in this field directs how to apply values that aren’t coincident with the given timestep (ref: Timestep) intervals. If “Yes” is entered, then any intervals entered here will be interpolated/averaged and that value will be used at the appropriate minute in the hour. If “No” is entered, then the value that occurs on the appropriate minute in the hour will be used as the schedule value.

For example, if “yes” is entered and the interval is every 15 minutes (say a value of 0 for the first 15 minutes, then .5 for the second 15 minutes) AND there is a 10 minute timestep for the simulation: the value at 10 minutes will be 0 and the value at 20 minutes will be .25. For the same input entries but “no” for this field, the value at 10 minutes will be 0 and the value at 20 minutes will be .5.

Field-Set: Time and Value (extensible object)

To specify each interval, both an “until” time (which includes the designated time) and the value must be given.

Field: Time

The value of each field should represent clock time (standard) in the format “Until: HH:MM”. 24 hour clock format (i.e. 1PM is 13:00) is used. Note that Until: 7:00 includes all times up through 07:00 or 7am.

Field: Value

This represents the actual value to be passed to the simulation at the appropriate timestep. (Using interpolation value as shown above). Limits on the values are indicated by the Schedule Type Limits Name field of this object.

Schedule:Day:List

To facilitate possible matches to externally generated data intervals, this object has been included. In similar fashion to the Schedule:Day:Interval object, this object can also include “sub-hourly” values but must represent a complete day in its list of values.

Field: Name

This field should contain a unique (within all day schedules) designation for this schedule. It is referenced by week schedules to define the appropriate schedule values.

Field: Schedule Type Limits Name

Field: Interpolate to Timestep

For example, if “yes” is entered and the minutes per item is 15 minutes (say a value of 0 for the first 15 minutes, then .5 for the second 15 minutes) AND there is a 10 minute timestep for the simulation: the value at 10 minutes will be 0 and the value at 20 minutes will be .25. For the same input entries but “no” for this field, the value at 10 minutes will be 0 and the value at 20 minutes will be .5.

Field: Minutes Per Item

This field allows the “list” interval to be specified in the number of minutes for each item. The value here must be <= 60 and evenly divisible into 60 (same as the timestep limits).

Field Value 1 (same definition for each value – up to 1440 (24*60) allowed)

Week Schedule(s)

The week schedule object(s) perform the task of assigning the day schedule to day types in the simulation. The basic week schedule is shown next.

Schedule:Week:Daily

Field: Name

This field should contain a unique (within all WeekSchedules) designation for this schedule. It is referenced by Schedules to define the appropriate schedule values.

Field: Schedule Day Name Fields (12 day types – Sunday, Monday, … )

These fields contain day schedule names for the appropriate day types. Days of the week (or special days as described earlier) will then use the indicated hourly profile as the actual schedule value.

Schedule:Week:Compact

Further flexibility can be realized by using the Schedule:Week:Compact object. In this the fields, after the name is given, a “for” field is given for the days to be assigned and then a dayschedule name is used.

Field:Name

This field should contain a unique (within all WeekSchedules) designation for this schedule. It is referenced by Schedules to define the appropriate schedule values.

Field-Set – DayType List#, Schedule:Day Name #

Each assignment is made in a pair-wise fashion. First the “days” assignment and then the dayschedule name to be assigned. The entire set of day types must be assigned or an error will result.

Field: DayType List #

This field can optionally contain the prefix “For” for clarity. Multiple choices may then be combined on the line. Choices are: Weekdays, Weekends, Holidays, Alldays, SummerDesignDay, WinterDesignDay, Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, CustomDay1, CustomDay2. In fields after the first “for”, AllOtherDays may also be used.

Field: Schedule:Day Name #

This field contains the name of the day schedule (any of the Schedule:Day object names) that is to be applied for the days referenced in the prior field.

Schedule:Year

The yearly schedule is used to cover the entire year using references to week schedules (which in turn reference day schedules). If the entered schedule does not cover the entire year, a fatal error will result.

Field: Name

This field should contain a unique (between Schedule:Year, Schedule:Compact, and Schedule:File) designation for the schedule. It is referenced by various “scheduled” items (e.g. Lights, People, Infiltration) to define the appropriate schedule values.

Field: Schedule Type Limits Name

Field Set (WeekSchedule, Start Month and Day, End Month and Day)

Each of the designated fields is used to fully define the schedule values for the indicated time period). Up to 53 sets can be used. An error will be noted and EnergyPlus will be terminated if an incomplete set is entered. Missing time periods will also be noted as warning errors; for these time periods a zero (0.0) value will be returned when a schedule value is requested. Each of the sets has the following 5 fields:

Field: Schedule Week Name #

This field contains the appropriate WeekSchedule name for the designated time period.

Field: Start Month #

Field: Start Day #

Field: End Month #

Field: End Day #

Note that there are many possible periods to be described. An IDF example with a single period:

The following definition will generate an error (if any scheduled items are used in the simulation):

Schedule:Compact

For flexibility, a schedule can be entered in “one fell swoop”. Using the Schedule:Compact object, all the features of the schedule components are accessed in a single command. Like the “regular” schedule object, each schedule:compact entry must cover all the days for a year. Additionally, the validations for DaySchedule (i.e. must have values for all 24 hours) and WeekSchedule (i.e. must have values for all day types) will apply. Schedule values are “given” to the simulation at the zone timestep, so there is also a possibility of “interpolation” from the entries used in this object to the value used in the simulation.

This object is an unusual object for description. For the data the number of fields and position are not set, they cannot really be described in the usual Field # manner. Thus, the following description will list the fields and order in which they must be used in the object. The name and schedule type are the exceptions:

Field: Name

Field: Schedule Type Limits Name

Field-Set (Through, For, Interpolate, Until, Value)

Each compact schedule must contain the elements Through (date), For (days), Interpolate (optional), Until (time of day) and Value. In general, each of the “titled” fields must include the “title”.

Field: Through

This field starts with “Through:” and contains the ending date for the schedule period (may be more than one). Refer to Table 3. Date Field Interpretation for information on date entry – note that only Month-Day combinations are allowed for this field. Each “through” field generates a new WeekSchedule named “Schedule Name”_wk_# where # is the sequential number for this compact schedule.

Field: For

This field starts with “For:” and contains the applicable days (reference the compact week schedule object above for complete description) for the 24 hour period that must be described. Each “for” field generates a new DaySchedule named “Schedule Name”_dy_# where # is the sequential number for this compact schedule.

Field: Interpolate (optional)

This field, if used, starts with “Interpolate:” and contains the word “Yes” or “No”. If this field is not used, it should not be blank – rather just have the following field appear in this slot. The definition of “Interpolate” in this context is shown in the interval day schedule above.

Field: Until

This field contains the ending time (again, reference the interval day schedule discussion above) for the current days and day schedule being defined.

Field: Value

Schedule:Constant

The constant schedule is used to assign a constant hourly value. This schedule is created when a fixed hourly value is desired to represent a period of interest (e.g., always on operation mode for supply air fan).

Field: Name

This field should contain a unique name designation for this schedule. It is referenced by Schedules to define the appropriate schedule value.

Field: Schedule Type Limits Name

Field: Hourly Value

This field contains a constant real value. A fixed value is assigned as an hourly value.

Schedule:File

At times, data is available from a building being monitored or for factors that change throughout the year. The Schedule:File object allows this type of data to be used in EnergyPlus as a schedule. Schedule:File can also be used to read in hourly schedules computed by other software or developed in a spreadsheet or other utility.

The format for the data file referenced is a text file with values separated by commas (or other optional delimiters) with one line per hour. The file may contain header lines that are skipped. The file should contain values for an entire year (8760 or 8784 lines of data) or a warning message will be issued. Multiple schedules may be created using a single external data file or multiple external data files may be used. The first row of data must be for January 1, hour 1.

Schedule:File may be used along with the FuelFactors object and TDV files in the DataSets directory to compute Time Dependent Valuation based source energy as used by the California Energy Commission’s Title 24 Energy Code. See Fuel Factor for more discussion on Time Dependent Valuation.

Field: Name

Field: Schedule Type Limits Name

Field: File Name

This field contains the name of the file that contains the data for the schedule. The field should include a full path with file name. The field must be <= 100 characters. The file name must not include commas or an exclamation point. A relative path or a simple file name will not work with version 6.0 or later when using EP-Launch due to the use of temporary directories as part of the execution of EnergyPlus. If using RunEPlus.bat to run EnergyPlus from the command line, a relative path or a simple file name may work if RunEPlus.bat is run from the folder that contains EnergyPlus.exe.

Field: Column Number

The column that contains the value to be used in the schedule. The first column is column one. If no data for a row appears for a referenced column the value of zero is used for the schedule value for that hour.

Field: Rows to Skip at Top

Many times the data in a file contains rows (lines) that are describing the files or contain the names of each column. These rows need to be skipped and the number of skipped rows should be entered for this field. The next row after the skipped rows must contain data for January 1, hour 1.

Field: Number of Hours of Data

The value entered in this field should be either 8760 or 8784 as the number of hours of data. 8760 does not include the extra 24 hours for a leap year (if needed). 8784 will include the possibility of leap year data which can be processed according to leap year indicators in the weather file or specified elsewhere. Note if the simulation does not have a leap year specified but the schedule file contains 8784 rows of data, the first 8760 rows of data will be used. The schedule manager will not know to skip the 24 rows representing Feburary 29.

Field: Column Separator

This field specifies the character used to separate columns of data if the file has more than one column. The choices are: Comma, Tab, Fixed (spaces fill each column to a fixed width), or Semicolon. The default is Comma.

Schedule Outputs

An optional report can be used to gain the values described in the previous Schedule objects. This is a condensed reporting that illustrates the full range of schedule values – in the style of input: DaySchedule, WeekSchedule, Annual Schedule.

This report is placed on the eplusout.eio file. Details of this reporting are shown in the Output Details and Examples document.

Schedule Value Output

Schedule Value

This is the schedule value (as given to whatever entity that uses it). It has no units in this context because values may be many different units (i.e. temperatures, fractions, watts). For best results, you may want to apply the schedule name when you use this report variable to avoid output proliferation. For example, the following reporting should yield the values shown above, depending on day of week and day type:

Group – Surface Construction Elements

This group of objects describes the physical properties and configuration for the building envelope and interior elements. That is, the walls, roofs, floors, windows, doors for the building.

Specifying the Building Envelope

Building element constructions in EnergyPlus are built from the basic thermal and other material property parameters in physical constructions. Materials are specified by types and named. Constructions are defined by the composition of materials. Finally, surfaces are specified for the building with geometric coordinates as well as referenced constructions.

Material and Material Properties

There are several material “types” which may be used to describe layers within opaque construction elements. The choice of which of these types to use is left up to the user. However, some guidance as to which material type to use is appropriate before describing each in detail. The opaque types are:

Material is the “preferred” type of material. This requires knowledge of many of the thermal properties of the material, but it allows EnergyPlus to take into account the thermal mass of the material and thus allows the evaluation of transient conduction effects. Material:NoMass is similar in nature but only requires the thermal resistance (R-value) rather than the thickness, thermal conductivity, density, and specific heat. Note that using a simple R-value only material forces EnergyPlus to assume steady state heat conduction through this material layer. Finally, Material:AirGap should only be used for an air gap between other layers in a construction. This type assumes that air is sufficiently lightweight to require only an R-value. In addition, since it is not exposed to any external environment, surface properties such as absorptance are not necessary. Material:RoofVegetation is used to help model “green roofs”. Material:InfraredTransparent is used similarly to the NoMass materials. Each of these materials is described in more detail below.

There are several material additions that can be made to the basic material properties. These additional material types are:

These material property objects are used in conjunction with the basic material specification and reference back to the name of the basic material type. Without the basic material type specified the program, will give a severe error and terminate. For example, specifying the moisture materials and changing the HeatBalanceAlgorithm to a moisture simulation will allow the moisture simulation to take place.

Material

This definition should be used when the four main thermal properties (thickness, conductivity, density, and specific heat) of the material are known. This syntax is used to describe opaque construction elements only.

Field: Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data (ref: Construction).

Field: Roughness

This alpha field defines the relative roughness of a particular material layer. This parameter only influences the convection coefficients, more specifically the exterior convection coefficient. A special keyword is expected in this field with the options being “VeryRough”, “Rough”, “MediumRough”, “MediumSmooth”, “Smooth”, and “VerySmooth” in order of roughest to smoothest options.

Field: Thickness

Field: Conductivity

This field is used to enter the thermal conductivity of the material layer. Units for this parameter are W/(m-K). Thermal conductivity must be greater than zero.

Field: Density

This field is used to enter the density of the material layer in units of kg/m³. Density must be a positive quantity.

Field: Specific Heat

This field represents the specific heat of the material layer in units of J/(kg-K). Note that these units are most likely different than those reported in textbooks and references which tend to use kJ/(kg-K) or J/(g-K). They were chosen for internal consistency within EnergyPlus. Only positive values of specific heat are allowed.

Field: Thermal Absorptance

The thermal absorptance field in the Material input syntax represents the fraction of incident long wavelength radiation that is absorbed by the material. This parameter is used when calculating the long wavelength radiant exchange between various surfaces and affects the surface heat balances (both inside and outside as appropriate). For long wavelength radiant exchange, thermal emissivity and thermal emittance are equal to thermal absorptance. Values for this field must be between 0.0 and 1.0 (with 1.0 representing “black body” conditions).

Field: Solar Absorptance

The solar absorptance field in the Material input syntax represents the fraction of incident solar radiation that is absorbed by the material. Solar radiation includes the visible spectrum as well as infrared and ultraviolet wavelengths. This parameter is used when calculating the amount of incident solar radiation absorbed by various surfaces and affects the surface heat balances (both inside and outside as appropriate). If solar reflectance (or reflectivity) data is available, then absorptance is equal to 1.0 minus reflectance (for opaque materials). Values for this field must be between 0.0 and 1.0.

Field: Visible Absorptance

The visible absorptance field in the Material input syntax represents the fraction of incident visible wavelength radiation that is absorbed by the material. Visible wavelength radiation is slightly different than solar radiation in that the visible band of wavelengths is much more narrow while solar radiation includes the visible spectrum as well as infrared and ultraviolet wavelengths. This parameter is used when calculating the amount of incident visible radiation absorbed by various surfaces and affects the surface heat balances (both inside and outside as appropriate) as well as the daylighting calculations. If visible reflectance (or reflectivity) data is available, then absorptance is equal to 1.0 minus reflectance (for opaque materials). Values for this field must be between 0.0 and 1.0.

Material:NoMass

Use this definition when only the thermal resistance (R value) of the material is known. This object is used to describe opaque construction elements.

Field: Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data (ref: Construction, SurfaceControl:MoveableInsulation).

Field: Roughness

This alpha field defines the relative roughness of a particular material layer. This parameter only influences the convection coefficients, more specifically the exterior convection coefficient. A keyword is expected in this field with the options being “VeryRough”, “Rough”, “MediumRough”, “MediumSmooth”, “Smooth”, and “VerySmooth” in order of roughest to smoothest options.

Field: Thermal Resistance

This field is used to enter the thermal resistance (R-value) of the material layer. Units for this parameter are (m²-K)/W. Thermal resistance must be greater than zero. Note that most R-values in the USA are calculated in Inch-Pound units and must be converted to the SI equivalent.

Field: Thermal Absorptance

Field: Solar Absorptance

Field: Visible Absorptance

Material:InfraredTransparent

A Infrared Transparent surface is similar to a resistance-only surface. The idd object for this type of surface is shown below. The surface will actually participate in the transfer of visible and solar radiation by doing a wavelength transformation and making all short wave length radiation that is incident on the surface into long wave length radiation and having it participate in the long wavelength radiant exchange. Note the ConvectionCoefficient instructions that follow the Infrared Transparent construction object below.

Field: Name

This field contains the unique name (across all Material objects) for the Infrared Transparent material.

A Infrared Transparent surface should not participate in a convective/conductive exchange between the zones it separates. In order to minimize this effect, the ConvectionCoefficients object must be used for the surfaces referencing the Infrared Transparent (IRT) construction.

An example idf object specification for use with the IRT surface is shown below. Note that surfaces are not described in this example

Material:AirGap

This material is used to describe the air gap in an opaque construction element. Glass elements use a different property (WindowGas) to describe the air between two glass layers.

Field: Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data (ref: Construction).

Field: Thermal Resistance

MaterialProperty:MoisturePenetrationDepth:Settings

This material is used to describe the five moisture material properties that are used in the EMPD (Effective Moisture Penetration Depth) heat balance solution algorithm (known there as MoisturePenetrationDepthConductionTransferFunction). The EMPD algorithm is a simplified, lumped moisture model that simulates moisture storage and release from interior surfaces. The model uses "actual" convective mass transfer coefficients that are determined by existing heat and mass transfer relationships, e.g. the Lewis relation. An effective moisture penetration depth may be determined from either experimental or detailed simulation data by using actual surface areas and moisture sorption isotherms.

This moisture model will be used when the appropriate EMPD moisture materials are specified and the Solution Algorithm parameter is set to EMPD.

Field: Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data (ref: Construction).

Field: Moisture Penetration Depth

This field is used to enter the effective moisture penetration depth of the material layer. Units for this parameter are (m).

Field: Constants to Define Moisture Equilibrium Equation

The next four fields, coefficients “a”, “b”, “c”, and “d”, help define the sorption isotherm curve used for building materials under equilibrium conditions. They are used to define the relationship between the material’s moisture content and the surface air relative humidity (ref: Effective Moisture Penetration Depth (EMPD) Model in the Engineering Reference):

a,b,c,d = Coefficients to define the relationship between the material’s moisture content and the surface air relative humidity

U = Moisture content defined as the mass fraction of water contained in a material [kg/kg]

The next four fields are dimensionless coefficients:

Field: Moisture Equation Coefficient a

Field: Moisture Equation Coefficient b

Field: Moisture Equation Coefficient c

Field: Moisture Equation Coefficient d

Ann IDF example showing how it is used in conjunction with Material in synchronous pairs:

Moisture Penetration Depth (EMPD) Outputs

The following variables apply only to surfaces, where the material assigned to the inside layers is MaterialProperty:MoisturePenetrationDepth:Settings. The EMPD (Effective Moisture Penetration Depth) moisture balance solution algorithm is used to calculate the inside surface moisture levels.

Inside Surface Vapor Density [kg/m3]

The vapor density at the inside surface, where the EMPD moisture balance solution algorithm is applied.

Inside Surface Humidity Ratio []

The humidity ratio at the inside surface, where the EMPD moisture balance solution algorithm is applied.

Inside Surface Relative Humidity [%]

The relative humidity at the inside surface, where the EMPD moisture balance solution algorithm is applied.

MaterialProperty:PhaseChange

Advanced/Research Usage: This material is used to describe the temperature dependent material properties that are used in the Conduction Finite Difference solution algorithm. This conduction model is done when the appropriate materials are specified and the Solution Algorithm parameter is set to ConductionFiniteDifference. This permits simulating temperature dependent thermal conductivity and phase change materials (PCM) in EnergyPlus.

Field: Name

This field is a regular material name specifying the material with which this additional temperature dependent property information will be associated.

Field: Temperature Coefficient for Thermal Conductivity

This field is used to enter the temperature dependent coefficient for thermal conductivity of the material. Units for this parameter are (W/(m-K²). This is the thermal conductivity change per unit temperature excursion from 20 C. The conductivity value at 20 C is the one specified with the basic material properties of the regular material specified in the name field. The thermal conductivity is obtained from:

Field Set: Temperature-Enthalpy

The temperature – enthalpy set of inputs specify a two column tabular temperature-enthalpy function for the basic material. Sixteen pairs can be specified. Specify only the number of pairs necessary. The tabular function must cover the entire temperature range that will be seen by the material in the simulation. It is suggested that the function start at a low temperature, and extend to 100C. Note that the function has no negative slopes and the lowest slope that will occur is the base material specific heat. Enthalpy contributions of the phase change are always added to the enthalpy that would result from a constant specific heat base material. An example of a simple enthalpy temperature function is shown below.

Field: Temperature x

This field is used to specify the temperature of the temperature-enthalpy function for the basic material. Units are C.

Field: Enthalpy x

This field specifies the enthalpy that corresponds to the previous temperature of the temperature-enthalpy function. Units are J/kg.

Note, the following Heat Balance Algorithm is necessary (only specified once). Also, when using ConductionFiniteDifference, it is more efficient to set the zone timestep shorter than those used for the ConductionTransferFunction solution algorithm. It should be set to 12 timesteps per hour or greater, and can range up to 60.

MaterialProperty:VariableThermalConductivity

This object is used to describe the temperature dependent material properties that are used in the CondFD (Conduction Finite Difference) solution algorithm. This conduction model is used when the appropriate CondFD materials are specified and the Solution Algorithm parameter is set to condFD.

Field: Name

This field is a regular material name specifying the material with which this additional temperature dependent property information will be associated.

Field Set: Temperature-Thermal Conductivity

The temperature – conductivity set of inputs specify a two column tabular temperature-thermal conductivity function for the basic material. Ten pairs can be specified. Specify only the number of pairs necessary.

Field: Temperature x

This field is used to specify the temperature of the temperature-conductivity function for the basic material. Units are C.

Field: Thermal Conductivity x

This field specifies the enthalpy that corresponds to the previous temperature of the temperature-enthalpy function. Units are W/m-K.

Note, the following Heat Balance Algorithm is necessary (only specified once). Also, when using Conduction Finite Difference, it is more efficient to set the zone time step shorter than those used for the Conduction Transfer Function solution algorithm. It should be set to 12 time steps per hour or greater, and can range up to 60.

Conduction Finite Difference (CondFD) Outputs

The Conduction Finite Difference and the Conduction Finite Difference Simplified solution algorithms both use a finite difference solution technique, the surfaces are divided into a nodal arrangement. (Simplfied algorithm uses only two nodes). In order to see detailed node infomation, three output variables are available. They provide the node temperatures, the inside heat flux and the outside heat flux.

The following output variables are applicable to all opaque heat transfer surfaces when using Solution Algorithms ConductionFiniteDifference or ConductionFiniteDifferenceSimplified:

CondFD Outside Surface Heat Flux [W/m2]

The heat flux at the outside face of the surface that is being simulated with ConductionFiniteDifference or ConductionFiniteDifferenceSimplified.

CondFD Inside Surface Heat Flux [W/m2]

The heat flux at the inside face of the surface that is being simulated with ConductionFiniteDifference or ConductionFiniteDifferenceSimplified.

CondFD Nodal Temperature [C]

This will output temperatures for each node in the surfaces being simulated with ConductionFiniteDifference or ConductionFiniteDifferenceSimplified. The key values for this output variable are the surface name plus node number, e.g. “ZN001:WALL001 Node #1:CondFD Nodal Temperature[C].” The nodes are numbered from outside to inside of the surface.

MaterialProperty:HeatAndMoistureTransfer:Settings

Advanced/Research Usage. This object is used to describe two of the seven additional material properties needed for the CombinedHeatAndMoistureFiniteElement heat balance solution algorithm. The settings object is used when the solutions algorithm is set to CombinedHeatAndMoistureFiniteElement and the appropriate material properties are assigned to each material. This permits the simulation of the moisture dependant thermal properties of the material as well as the transfer of moisture through, into and out of the material into the zone or exterior.

In addition to the Porosity and Initial Water content properties described here, five additional properties, described by tabulated relationships between variables, are required. These properties are;

All materials in a construction are required to have all material properties defined for HAMT to work.

Within the MaterialProperty:HeatAndMoistureTransfer:Settings object the following fields are defined.

Field: Material Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data.

Field: Porosity

The porosity of a material is the maximum fraction, by volume, of a material that can be taken up with water. The units are [m3/m3].

Field: Initial Water Content Ratio

For this solution algorithm, the initial water content is assumed to be distributed evenly through the depth of the material. The units are [kg/kg].

Below is an example input for the porosity and initial water content of a material.

MaterialProperty:HeatAndMoistureTransfer:SorptionIsotherm

Advanced/Research Usage. This material property is used in conjunction with the CombinedHeatAndMoistureFiniteElement heat balance solution algorithm.

The Isotherm data relates the moisture, or water content [kg/m3] of a material with the relative humidity (RH). The water content is expected to increase as relative humidity increases, starting at zero content at 0.0relative humidity fraction and reaching a maximum, defined by the porosity, at 1.0 relative humidity fraction, which corresponds to 100% relatve humidity. Relative humidities are entered as fraction for this object ranging from 0.0 to 1.0. These two extremes (0.0 and 1.0) are automatically set by the HAMT solution. However, if they are entered they will be used as extra data points. Data should be provided with increasing RH and moisture content up to as high an RH as possible to provide a stable solution. One possible reason for the following error message may be that a material has a very rapid increase in water content for a small change in RH, which can happen if the last entered water content point is at a low RH and the material has a very high porosity.

Another potential reason for this error being generated is the use of inappropriate values for Vapor Transfer Coefficients. See the SurfaceProperties:VaporCoefficients object in the Advanced Surface Concepts group.

Field: Material Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data.

Field: Number of data Coordinates

Field Set: Relative Humidity-Moisture Content

Field: Relative Humidity Fraction x

The relative humidity of the x^th coordinate. The relative humidity is entered as fraction, not in percent.

Field: Moisture Content x

MaterialProperty:HeatAndMoistureTransfer:Suction

Advanced/Research Usage. This material property is used in conjunction with the CombinedHeatAndMoistureFiniteElement heat balance solution algorithm.

The suction data relates the liquid transport coefficient, under suction, to the water content of a material. A data point at zero water content is required. The liquid transport coefficient at the highest entered water content value is used for all liquid transport coefficient values above this water content. These coefficients are used by HAMT when the rain flag is set in the weather file.

Field: Material Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data.

Field: Number of Suction points

Field Set: Moisture Content-Liquid Transport Coefficient

Field: Moisture Content x

Field: Liquid Transport Coefficient x

Below is an example input for a material liquid transport coefficient under suction.

MaterialProperty:HeatAndMoistureTransfer:Redistribution

Advanced/Research Usage. This material property is used in conjunction with the CombinedHeatAndMoistureFiniteElement heat balance solution algorithm.

The redistribution data relates the liquid transport coefficient to the water content of a material under normal conditions. A data point at zero water content is required. The liquid transport coefficient at the highest entered water content value is used for all liquid transport coefficient values above this water content. These coefficients are used by the Heat and Moisture Transfer algorithm when the rain flag is NOT set in the weather file.

Field: Material Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data.

Field: Number of Redistribution points

Field Set: Moisture Content-- Liquid Transport Coefficient

Field: Moisture Content x

Field: Liquid Transport Coefficient x

MaterialProperty:HeatAndMoistureTransfer:Diffusion

Advanced/Research Usage. This material property is used in conjunction with the CombinedHeatAndMoistureFiniteElement heat balance solution algorithm.

The MU data relates the vapor diffusion resistance factor (dimensionless) to the relative humidity as fraction(RH). A data point at zero RH is required. The vapor diffusion resistance factor at the highest entered relative humidity (RH) value is used for all vapor diffusion resistance factor values above this RH. The relative humidity maximum value in fraction is 1.0.

Field: Material Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data.

Field: Number of Data Pairs

Field Set: Relative Humidity-Vapor Diffusion Resistance Factor

Field: Relative Humidity Fraction #x

The moisture content of the x^th pair. The relative humidity is entered as fraction, not in percent.

Field: Vapor Diffusion Resistance Factor #x

MaterialProperty:HeatAndMoistureTransfer:ThermalConductivity

Advanced/Research Usage. This material property is used in conjunction with the CombinedHeatAndMoistureFiniteElement heat balance solution algorithm.

The thermal data relates the thermal conductivity [W/m-K] of a material to the moisture or water content [kg/m3]. A data point at zero water content is required. The thermal conductivity at the highest entered water content value is used for all thermal conductivity values above this water content. If this object is not defined for a material then the algorithm will use a constant value entered in the Material object for all water contents.

Field: Material Name

This field is a unique reference name that the user assigns to a particular material. This name can then be referred to by other input data.

Field: Number of Thermal Coordinates

Field Set: Moisture Content- Thermal Conductivity

Field: Moisture Content x

Field: Thermal Conductivity x

Heat and Moisture (HAMT) Outputs

HAMT Surface Water Content [kg/kg]

This output is the summed water content [kg/kg] of all cells in a surface expressed as a fraction of the mass of the water to the material mass.

HAMT Surface Interior Temperature [C]

This output is the temperature [C] on the internal “surface” of the surface.

Inside Surface Relative Humidity [%]

HAMT Surface Interior Relative Humidity [%]

This output is the relative humidity on the internal “surface” of the surface expressed as a percentage.

HAMT Surface Interior Vapor Pressure [Pa]

This output is the vapor pressure [Pa] on the internal “surface” of the surface.

HAMT Surface Exterior Temperature [C]

HAMT Surface Exterior Relative Humidity [%]

This output is the relative humidity on the external “surface” of the surface.

Detailed profile data for the variables Temperature[C], Relative Humidity [%] and Water Content [kg/kg] within each surface can also be reported. To calculate the heat and moisture transfer through surfaces HAMT splits up surfaces into discrete cells. Each cell is composed of a single material and has a position within the surface. HAMT automatically assigns cells to construction objects so that there are more cells closer to boundaries between materials and also at the “surfaces” of the surface. It is not possible for users to define their own cells. Each surface is made from a particular construction. The construction-surface relationship is output by HAMT to the eplusout.eio file with the following format.

The output also contains the HAMT cell origins and cell number for each construction – surface combination. The coordinate system origin is defined as the exterior surface of the construction. Users can select any one of the Temperature, Relative Humidity or Water Content variables for any cell to be reported, using the following naming scheme for the output variable.

So for example to output the temperature of the 10^th cell in a surface, eg “East Wall” would require the following output variable.

By selecting a whole range of these reports and using the information in the eplusout.eio file it is possible to build up a temperature profile of the surface.

Materials for Glass Windows and Doors

All the materials for glass windows and doors have the prefix “WindowMaterial”. The following WindowMaterial descriptions (Glazing, Glazing:RefractionExtinctionMethod, Gas, GasMixture, Shade, Screen and Blind) apply to glass windows and doors. The property definitions described herein for Glazing, Gas and GasMixture are supported by the National Fenestration Rating Council as standard.

“Front side” is the side of the layer opposite the zone in which the window is defined. “Back side” is the side closest to the zone in which the window is defined. Therefore, for exterior windows, “front side” is the side closest to the outdoors. For interior windows, “front side” is the side closest to the zone adjacent to the zone in which the window is defined.

The solar radiation transmitted by the window layers enters the zone and is a component of the zone load. The solar radiation absorbed in each solid layer (glass, shade, screen or blind) participates in the window layer heat balance calculation. The visible transmittance and reflectance properties of the window are used in the daylighting calculation.

WindowMaterial:Glazing

In the following, for exterior windows, “front side” is the side of the glass closest to the outside air and “back side” is the side closest to the zone the window is defined in. For interzone windows, “front side” is the side closest to the zone adjacent to the zone the window is defined in and “back side” is the side closest to the zone the window is defined in.

Field: Name

The name of the glass layer. It corresponds to a layer in a window construction.

Field: Optical Data Type

If Optical Data Type = SpectralAverage, the values you enter for solar transmittance and reflectance are assumed to be averaged over the solar spectrum, and the values you enter for visible transmittance and reflectance are assumed to be averaged over the solar spectrum and weighted by the response of the human eye. There is an EnergyPlus Reference Data Set for WindowMaterial:Glazing that contains spectral average properties for many different types of glass.

If Optical Data Type = Spectral, then, in the following field, you must enter the name of a spectral data set defined with the WindowGlassSpectralData object. In this case, the values of solar and visible transmittance and reflectance in the fields below should be blank.

Field: Window Glass Spectral Data Set Name

If Optical Data Type = Spectral, this is the name of a spectral data set defined with a WindowGlassSpectralData object.

Field: Thickness

Field: Solar Transmittance at Normal Incidence

Transmittance at normal incidence averaged over the solar spectrum. Used only when Optical Data Type = SpectralAverage.

For uncoated glass, when alternative optical properties are available—such as thickness, solar index of refraction, and solar extinction coefficient—they can be converted to equivalent solar transmittance and reflectance values using the equations given in “Conversion from Alternative Specification of Glass Optical Properties.”)

Field: Front Side Solar Reflectance at Normal Incidence

Front-side reflectance at normal incidence averaged over the solar spectrum. Used only when Optical Data Type = SpectralAverage.

Field: Back Side Solar Reflectance at Normal Incidence

Back-side reflectance at normal incidence averaged over the solar spectrum. Used only when Optical Data Type = SpectralAverage.

Field: Visible Transmittance at Normal Incidence

Transmittance at normal incidence averaged over the solar spectrum and weighted by the response of the human eye. Used only when Optical Data Type = SpectralAverage.

For uncoated glass, when alternative optical properties are available—such as thickness, visible index of refraction, and visible extinction coefficient—they can be converted to equivalent visible transmittance and reflectance values using the equations given in “Conversion from Alternative Specification of Glass Optical Properties.”)

Field: Front Side Visible Reflectance at Normal Incidence

Front-side reflectance at normal incidence averaged over the solar spectrum and weighted by the response of the human eye. Used only when Optical Data Type = SpectralAverage.

Field: Back Side Visible Reflectance at Normal Incidence

Back-side reflectance at normal incidence averaged over the solar spectrum and weighted by the response of the human eye. Used only when Optical Data Type = SpectralAverage.

Field: Infrared Transmittance at Normal Incidence

Field: Front Side Infrared Hemispherical Emissivity

Field: Back Side Infrared Hemispherical Emissivity

Field: Conductivity

Field: Dirt Correction Factor for Solar and Visible Transmittance

This is a factor that corrects for the presence of dirt on the glass. The program multiplies the fields “Solar Transmittance at Normal Incidence” and “Visible Transmittance at Normal Incidence” by this factor if the material is used as the outer glass layer of an exterior window or glass door.[2] If the material is used as an inner glass layer (in double glazing, for example), the dirt correction factor is not applied because inner glass layers are assumed to be clean. Using a material with dirt correction factor < 1.0 in the construction for an interior window will result in an error message.

From Appendix A, “Daylighting in Sports Halls, Report 2,” SportScotland, Nov. 2002
(www.sportscotland.org.uk)

The default value of the dirt correction factor is 1.0, which means the glass is clean.

It is assumed that dirt, if present, has no effect on the IR properties of the glass.

Field: Solar Diffusing

Takes values No (the default) and Yes. If No, the glass is transparent and beam solar radiation incident on the glass is transmitted as beam radiation with no diffuse component. If Yes, the glass is translucent and beam solar radiation incident on the glass is transmitted as hemispherically diffuse radiation with no beam component.[3] See Figure 8. Solar Diffusing = Yes should only be used on the innermost pane of glass in an exterior window; it does not apply to interior windows.

For both Solar Diffusing = No and Yes, beam is reflected as beam with no diffuse component (see Figure 8)

If, in the Building object, Solar Distribution = FullInteriorAndExterior, use of Solar Diffusing = Yes for glass in an exterior window will change the distribution of interior solar radiation from the window. The result is that beam solar radiation that would be transmitted by a transparent window and get absorbed by particular interior surfaces will be diffused by a translucent window and be spread over more interior surfaces. This can change the time dependence of heating and cooling loads in the zone.

In a zone with Daylighting:Detailed, translucent glazing---which is often used in skylights---will provide a more uniform daylight illuminance over the zone and will avoid patches of sunlight on the floor.

Figure 8. Comparison between transmittance properties of transparent glass (Solar Diffusing = No) and translucent glass (Solar Diffusing = Yes).

WindowMaterial:Glazing:RefractionExtinctionMethod

This is an alternative way of specifying glass properties. Index of refraction and extinction coefficient are given instead of the transmittance and reflectance values used in WindowMaterial:Glazing. However, unlike WindowMaterial:Glazing, WindowMaterial:Glazing:RefractionExtinctionMethod is restricted to cases where the front and back optical properties of the glass are the same. This means it cannot be used for glass with a coating on one side. In that case WindowMaterial:Glazing should be used. Also, unlike WindowMaterial:Glazing, WindowMaterial:Glazing:RefractionExtinctionMethod does not allow input of glass wavelength-by-wavelength (spectral) properties.

Field: Name

The name of the glass layer. It corresponds to a layer in a window construction.

Field: Thickness

Field: Solar Index of Refraction

Field: Solar Extinction Coefficient

Field: Visible Index of Refraction

Index of refraction averaged over the solar spectrum and weighted by the response of the human eye.

Field: Visible Extinction Coefficient

Extinction coefficient averaged over the solar spectrum and weighted by the response of the human eye (m^-1).

Field: Infrared Transmittance at Normal Incidence

Field: Infrared Hemispherical Emissivity

Long-wave hemispherical emissivity, assumed the same on both sides of the glass.

Field: Conductivity

Field: Dirt Correction Factor for Solar and Visible Transmittance

This is a factor that corrects for the presence of dirt on the glass. It multiplies the solar and visible transmittance at normal Incidence (which the program calculates from the input values of thickness, solar index of refraction, solar extinction coefficient, etc.) if the material is used as the outer glass layer of an exterior window or glass door. If the material is used as an inner glass layer (in double glazing, for example), the dirt correction factor is not applied because inner glass layers are assumed to be clean. Using a material with dirt correction factor < 1.0 in the construction for an interior window will result in an error message.

The default value of the dirt correction factor is 1.0, which means the glass is clean. It is assumed that dirt, if present, has no effect on the IR properties of the glass.

Field: Solar Diffusing

Takes values No (the default) and Yes. If No, the glass is transparent. If Yes, the glass is translucent and beam solar radiation incident on the glass is transmitted as hemispherically diffuse radiation with no beam component. Solar Diffusing = Yes should only be used on the innermost pane of glass in an exterior window; it does not apply to interior windows.

In a zone with Daylighting:Detailed, translucent glazing, which is often used in skylights, will provide a more uniform daylight illuminance over the zone and will avoid patches of sunlight on the floor.

Glass Optical Properties Conversion

Conversion from Glass Optical Properties Specified as Index of Refraction and Transmittance at Normal Incidence

The optical properties of uncoated glass are sometimes specified by index of refraction, n,
and transmittance at normal incidence, T.

The following equations show how to convert from this set of values to the transmittance and reflectance values required by WindowMaterial:Glazing. These equations apply only to uncoated glass, and can be used to convert either spectral-average solar properties or spectral-average visible properties (in general, n and T are different for the solar and visible). Note that since the glass is uncoated, the front and back reflectances are the same and equal to the R that is solved for in the following equations.

WindowMaterial:GlazingGroup:Thermochromic

Thermochromic (TC) materials have active, reversible optical properties that vary with temperature. Thermochromic windows are adaptive window systems for incorporation into building envelopes. Thermochromic windows respond by absorbing sunlight and turning the sunlight energy into heat. As the thermochromic film warms it changes its light transmission level from less absorbing to more absorbing. The more sunlight it absorbs the lower the light level going through it. By using the suns own energy the window adapts based solely on the directness and amount of sunlight. Thermochromic materials will normally reduce optical transparency by absorption and/or reflection, and are specular (maintaining vision).

A thermochromic window is defined with a Construction object which references a special layer defined with a WindowMaterial:GlazingGroup:Thermochromic object. The WindowMaterial:GlazingGroup:Thermochromic object further references a series of WindowMaterial:Glazing objects corresponding to each specification temperature of the TC layer.

This object specifies a layer of thermochromic glass, part of a thermochromic window. An example file ThermochromicWindow.idf is included in the EnergyPlus installation.

Field: Name

Field Set (Optical Data Temperature, Window Material Glazing Name) is extensible.

Field: Optical Data Temperature <N>

The temperature of the TC glass layer corresponding to the optical data of the TC layer. Unit is °C.

Field: Window Material Glazing Name <N>

The window glazing (defined with WindowMaterial:Glazing) name that provides the TC glass layer performance at the above specified temperature.

Construction,

window_const, !- Name

Usual Glass, !- Layer 1

AIR 6MM, !- Layer 2

TCGlazings, !- Layer 3

AIR 6MM, !- Layer 4

Usual Glass; !- Layer 5

WindowMaterial:Gas,

AIR 6MM, !- Name

Air, !- Gas Type

0.0063; !- Thickness {m}

! Added for thermochromic glazings

WindowMaterial:GlazingGroup:Thermochromic,

TCGlazings,

0 , TCGlazing0,

20, TCGlazing20,

25, TCGlazing25,

30, TCGlazing30,

35, TCGlazing35,

40, TCGlazing40,

45, TCGlazing45,

50, TCGlazing50,

55, TCGlazing55,

60, TCGlazing60,

65, TCGlazing65,

75, TCGlazing75,

85, TCGlazing85;

WindowMaterial:Glazing,

TCGlazing0, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing20, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing25, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing30, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing35, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing40, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing45, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing50, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing55, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing60, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing65, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing75, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:Glazing,

TCGlazing85, !- Name

SpectralAverage, !- Optical Data Type

, !- Window Glass Spectral Data Set Name

0.0030, !- Thickness

0.2442, !- Solar Transmittance at Normal Incidence

0.7058, !- Front Side Solar Reflectance at Normal Incidence

0.7058, !- Back Side Solar Reflectance at Normal Incidence

0.3192, !- Visible Transmittance at Normal Incidence

0.6308, !- Front Side Visible Reflectance at Normal Incidence

0.6308, !- Back Side Visible Reflectance at Normal Incidence

0.0000, !- Infrared Transmittance at Normal Incidence

0.9000, !- Front Side Infrared Hemispherical Emissivity

0.9000, !- Back Side Infrared Hemispherical Emissivity

0.0199, !- Conductivity

1.0000, !- Dirt Correction Factor for Solar and Visible Transmittance

No; !- Solar Diffusing

WindowMaterial:GlazingGroup:Thermochromic Outputs

Window Thermochromic Layer Temperature [C]

Window Thermochromic Layer Specification Temperature [C]

The temperature under which the optical data of the TC glass layer are specified.

The overall properties (U-factor/SHGC/VT) of the thermochromic windows at different specification temperatures are reported in the EIO file. These window constructions are created by EnergyPlus during run time. They have similar names with suffix “_TC_XX” where XX represents a specification temperature.

WindowMaterial:Gas

This object specifies the properties of the gas between the panes of a multi-pane window. Gas Type = Custom allows you to specify the properties of gases other than air, Argon, Krypton or Xenon. There is an EnergyPlus Reference Data Set for Material:WindowGas that contains several types of gas of different thicknesses. See Material:WindowGasMixture for the case that the gas fill is a mixture of different gases.

Field: Name

Field: Gas Type

The type of gas. The choices are Air, Argon, Krypton, or Xenon. If Gas Type = Custom you can use Conductivity Coefficient A, etc. to specify the properties of a different type of gas.

Field: Thickness

Properties for Custom Gas Types

The following entries are used only if Gas Type = Custom. The A and B coefficients are those in the following expression that gives a property value as a function of temperature in degrees K:

Field: Conductivity Coefficient A

Field: Conductivity Coefficient B

The B coefficient for gas conductivity (W/m-K²). Used only if Gas Type = Custom.

Field: Viscosity Coefficient A

Field: Viscosity Coefficient B

Field: Specific Heat Coefficient A

The A coefficient for gas specific heat (J/kg-K). Used only if Gas Type = Custom.

Field: Specific Heat Coefficient B

The B coefficient for gas specific heat (J/kg-K²). Used only if Gas Type = Custom.

WindowMaterial:GasMixture

This object allows you to specify the fill between the panes of a multi-pane window to be a mixture of two, three or four different gases chosen from air, argon, krypton and xenon. It can also be used if only one type of gas in the fill. In this case you can also use WindowMaterial:Gas. Note that the fractions of gas types in the mixture should add up to 1.0.

Field: Name

Field: Thickness

Field: Number of Gases in Mixture

Set: Gas Type-Fraction (up to 4)

Field: Gas 1 Type

The type of the first gas in the mixture. Choices are Air, Argon, Krypton and Xenon.

Field: Gas 1 Fraction

WindowMaterial:SimpleGlazingSystem

This model should be used with caution. There may be significant differences in performance between the simple window system and the usual more detailed model.

This input object differs from the other WindowMaterial objects in that it describes an entire glazing system rather than individual layers. This object is used when only very limited information is available on the glazing layers or when specific performance levels are being targeted. The layer by layer description offers superior method of modeling windows that should be used instead of this object when sufficient data are available. This object accesses a model that turns simple performance indices into a fuller model of the glazing system.

The performance indices are U-factor and Solar Heat Gain Coefficient, and optionally Visible Transmittance. The values for these performance indices can be selected by the user to represent either glazing-only windows (with no frame) or an average window performance that includes the frame. Inside the program the model produces an equivalent window glazing layer with no frame. The properties of the modeled glazing layer are reported to the EIO file using the IDF input object syntax for the WindowMaterial:Glazing input object. This equivalent layer could be reused in subsequent models if desired, however there will be important differences in the modeled window performance because the simple glazing system model includes its own special model for angular dependence when incident beam solar is not normal to the plane of the window.

When this object is referenced in a Construction object, it cannot be used with other glazing or gas material layers. Shades or blinds cannot be located between the glass, but these can be used on the inside or the outside of the glazing system. If the glazing system does have between-the-glass shades or blinds, then the U and SHGC values entered in this object should include the impacts of those layers. Adding window treatment layers such as shades or screens will alter the overall performance to be different than the performance levels prescribed in this object.

Field: Name

Field: U-Factor

This field describes the value for window system U-Factor, or overall heat transfer coefficient. Units are in W/m²·K. This is the rated (NFRC) value for U-factor under winter heating conditions. The U-factor is assumed to be for vertically mounted products. Although the maximum allowable input is U-7.0 W/m²·K, the effective upper limit of the glazings generated by the underlying model is around U-5.8 W/m²·K.

Field: Solar Heat Gain Coefficient

This field describes the value for SHGC, or solar heat gain coefficient. There are no units. This is the rated (NFRC) value for SHGC under summer cooling conditions and represents SHGC for normal incidence and vertical orientation.

Field: Visible Transmittance

This field is optional. If it is omitted, then the visible transmittance properties are taken from the solar properties. If it is included then the model includes it when developing properties for the glazing system. This is the rated (NFRC) value for visible transmittance at normal incidence.

WindowMaterial:Shade

This object specifies the properties of window shade materials. Reflectance and emissivity properties are assumed to be the same on both sides of the shade. Shades are considered to be perfect diffusers (all transmitted and reflected radiation is hemispherically-diffuse) with transmittance and reflectance independent of angle of incidence. There is an EnergyPlus Reference Data Set for WindowMaterial:Shade that contains properties of generic window shades.

Window shades can be on the inside of the window (“interior shades”), on the outside of the window (“exterior shades”), or between glass layers (“between-glass shades”). When in place, the shade is assumed to cover all of the glazed part of the window, including dividers; it does not cover any of the window frame, if present. The plane of the shade is assumed to be parallel to the glazing.

WindowMaterial:Shade can be used for diffusing materials such as drapery and translucent roller shades. For slat-type shading devices, like Venetian blinds, that have a strong angular dependence of transmission, absorption and reflection, it is better to use WindowMaterial:Blind. WindowMaterial:Screen should be used to model wire mesh insect screens where the solar and visible transmission and reflection properties vary with the angle of incidence of solar radiation.

Transmittance and reflectance values for drapery material with different color and openness of weave can be obtained from manufacturers or determined from 2001 ASHRAE Fundamentals, Chapter 30, Fig. 31.

Method 1:

1) Define the construction of the window without the shade, the so-called “bare” construction.

2) Reference the bare construction in the FenestrationSurface:Detailed for the window.

4) Define a WindowProperty:ShadingControl for the window in which you (a) specify that this WindowMaterial:Shade is the window’s shading device and (b) specify how the shade is controlled.

Method 2:

1) Define the Construction of the window without the shade, the so-called “bare” construction.

2) Reference the bare construction in the FenestrationSurface:Detailed for the window.

4) Define another Construction, called the “shaded construction,” that includes the WindowMaterial:Shade.

5) Define a WindowProperty:ShadingControl for the window in which you (a) reference the shaded construction and (b) specify how the shade is controlled.

Note that WindowProperty:ShadingControl has to be used with either method, even if the shade is in place at all times. You will get an error message if you try to reference a shaded construction directly from FenestrationSurface:Detailed.

Field: Name

Name of the shade. It is referenced as an inside or outside layer in a window construction.

Field: Solar Transmittance

Transmittance averaged over the solar spectrum. Assumed independent of incidence angle.

Field: Solar Reflectance

Reflectance averaged over the solar spectrum. Assumed same on both sides of shade and independent of incidence angle.

Field: Visible Transmittance

Transmittance averaged over the solar spectrum and weighted by the response of the human eye. Assumed independent of incidence angle.

Field: Visible Reflectance

Reflectance averaged over the solar spectrum and weighted by the response of the human eye. Assumed same on both side of shade and independent of incidence angle.

Field: Thermal Hemispherical Emissivity

Effective long-wave emissivity. Assumed same on both sides of shade. We can approximate this effective emissivity, ε_eff, as follows. Let η be the “openness” the shade, i.e., the ratio of the area of openings in the shade to the overall shade area (see Field: Air-Flow Permeability, below). Let the emissivity of the shade material be ε. Then

Field: Thermal Transmittance

Effective long-wave transmittance. Assumed independent of incidence angle. We can approximate this effective long-wave transmittance, τ_eff, as follows. Let η be the “openness” the shade, i.e., the ratio of the area of openings in the shade to the overall shade area. Let the long-wave transmittance of the shade material be τ. Then

Field: Thickness

Thickness of the shade material (m). If the shade is not flat, such as for pleated pull-down shades or folded drapery, the average thickness normal to the plane of the shade should be used.

Field: Conductivity

Field: Shade to Glass Distance

Distance from shade to adjacent glass (m). This is denoted by s in Figure 9 and Figure 10, below. If the shade is not flat, such as for pleated pull-down shades or folded drapery, the average shade-to-glass distance should be used. (The shade-to-glass distance is used in calculating the natural convective air flow between glass and shade produced by buoyancy effects.). Note used for between-glass shades.

Field: Top Opening Multiplier

Effective area for air flow at the top of the shade divided by sW, the horizontal area between glass and shade (see Figures below).

Field: Bottom Opening Multiplier

Effective area for air flow at the bottom of the shade divided by sW, the horizontal area between glass and shade (see Figures below).

Field: Left-Side Opening Multiplier

Effective area for air flow at the left side of the shade divided by sH, the vertical area between glass and shade (see Figures below).

Field: Right-Side Opening Multiplier

Effective area for air flow at the right side of the shade divided by sH, the vertical area between glass and shade (see Figures below).

Field: Field: Air-Flow Permeability

The fraction of the shade surface that is open to air flow, i.e., the total area of openings (“holes”) in the shade surface divided by the shade area, HW. If air cannot pass through the shade material, Air-Flow Permeability = 0. For drapery fabric and screens the Air-Flow Permeability can be taken as the “openness” of the fabric (see 2001 ASHRAE Fundamentals, Chapter 30, Fig. 31), which is 0.0 to 0.07 for closed weave, 0.07 to 0.25 for semi-open weave, and 0.25 and higher for open weave.

Figure 9. Vertical section (a) and perspective view (b) of glass and interior shade layers showing variables used in the gap air flow analysis. In (b), the air-flow opening areas A_bot, A_top, A_l, A_r and A_h are shown schematically. See Engineering Manual for definition of thermal variables.

Figure 10. Examples of air-flow openings for an interior shade covering glass of height H and width W. Not to scale. (a) Horizontal section through shade with openings on the left and right sides (top view). (b) Vertical section through shade with openings at the top and bottom (side view). In (a) Left-Side Opening Multiplier = A_l /sH = min(l/s,1) and Right-Side Opening Multiplier = A_r /sH = min(r/s,1). In (b) Top Opening Multiplier = A_top /sW = t/s and Bottom Opening Multiplier = A_bot /sW = b/s.

WindowMaterial:Blind

This object specifies the properties of a window blind consisting of flat, equally-spaced slats. Unlike window shades, which are modeled as perfect diffusers, window blinds have solar and visible transmission and reflection properties that strongly depend on slat angle and angle of incidence of solar radiation. There is an EnergyPlus Reference Data Set for WindowMaterial:Blind that contains properties of generic window blinds.

Blinds can be located on the inside of the window (“interior blinds”), on the outside of the window (“exterior blinds”), or between two layers of glass (“between-glass blinds”). When in place, the blind is assumed to cover all of the glazed part of the window, including dividers; it does not cover any of the window frame, if present. The plane of the blind is assumed to be parallel to the glazing. When the blind is retracted it is assumed to cover none of the window. The solar and thermal effects of the blind’s support strings, tapes or rods are ignored. Slat curvature, if present, is ignored.

Method 1:

1) Define the construction of the window without the blind, the so-called “bare” construction.

2) Reference the bare construction in the FenestrationSurface:Detailed for the window.

4) Define a WindowProperty:ShadingControl for the window in which you (a) specify that this WindowMaterial:Blind is the window’s shading device and (b) specify how the blind is controlled.

Method 2:

1) Define the Construction of the window without the blind, the so-called “bare” construction.

2) Reference the bare construction in the FenestrationSurface:Detailed for the window.

4) Define another Construction, called the “shaded construction,” that includes the WindowMaterial:Blind.

5) Define a WindowProperty:ShadingControl for the window in which you (a) reference the shaded construction and (b) specify how the blind is controlled.

Note that WindowProperty:ShadingControl has to be used with either method, even if the blind is in place at all times. You will get an error message if you try to reference a construction with a blind directly from Window objects (FenestrationSurface:Detailed or Window).

Note also that WindowProperty:ShadingControl is used to determine not only when the blind is in place, but how its slat angle is controlled.

Field: Name

Name of the blind. It is referenced as a layer in a window construction (ref: Construction) or as a “Material Name of Shading Device” in a WindowProperty:ShadingControl object.

Field: Slat Orientation

The choices are Horizontal and Vertical. “Horizontal” means the slats are parallel to the bottom of the window; this is the same as saying that the slats are parallel to the X-axis of the window. “Vertical” means the slats are parallel to Y-axis of the window.

Field: Slat Width

Field: Slat Separation

The distance between the front of a slat and the back of the adjacent slat (m). See Figure 11.

Field: Slat Thickness

Field: Slat Angle

The angle (degrees) between the glazing outward normal and the slat outward normal, where the outward normal points away from the front face of the slat (degrees). See Figure 11.

If the WindowProperty:ShadingControl for the blind has Type of Slat Angle Control for Blinds = FixedSlatAngle, the slat angle is fixed at “Slat Angle.”

If Type of Slat Angle Control for Blinds = BlockBeamSolar, the program automatically adjusts the slat angle so as just block beam solar radiation. In this case the value of “Slat Angle” is used only when the blind is in place and there is no beam solar radiation incident on the blind.

If Type of Slat Angle Control for Blinds = ScheduledSlatAngle, the slat angle is variable. In this case “Slat Angle” is not applicable and the field should be blank.

If Type of Slat Angle Control for Blinds = FixedSlatAngle and “Slat Angle” is less than the minimum or greater than the maximum allowed by Slat Width, Slat Separation and Slat Thickness, the slat angle will be reset to the corresponding minimum or maximum and a warning will be issued.

Field: Slat Conductivity

Field: Slat Beam Solar Transmittance

The beam solar transmittance of the slat, assumed to be independent of angle of incidence on the slat. Any transmitted beam radiation is assumed to be 100% diffuse (i.e., slats are translucent).

Field: Front Side Slat Beam Solar Reflectance

The beam solar reflectance of the front side of the slat, assumed to be independent of angle of incidence (matte finish). This means that slats with a large specularly-reflective component (shiny slats) are not well modeled.

Field: Back Side Slat Beam Solar Reflectance

The beam solar reflectance of the back side of the slat, assumed to be independent of angle of incidence (matte finish). This means that slats with a large specularly-reflective component (shiny slats) are not well modeled.

Field: Slat Diffuse Solar Transmittance

The slat transmittance for hemispherically diffuse solar radiation. This value should equal “Slat Beam Solar Transmittance.”

Field: Front Side Slat Diffuse Solar Reflectance

The front-side slat reflectance for hemispherically diffuse solar radiation. This value should equal “Front Side Slat Beam Solar Reflectance.”

Field: Back Side Slat Diffuse Solar Reflectance

The back-side slat reflectance for hemispherically diffuse solar radiation. This value should equal “Back Side Slat Beam Solar Reflectance.”

Field: Slat Beam Visible Transmittance

The beam visible transmittance of the slat, assumed to be independent of angle of incidence on the slat. Any transmitted visible radiation is assumed to be 100% diffuse (i.e., slats are translucent).

Field: Front Side Slat Beam Visible Reflectance

The beam visible reflectance on the front side of the slat, assumed to be independent of angle of incidence (matte finish). This means that slats with a large specularly-reflective component (shiny slats) are not well modeled.

Field: Back Side Slat Beam Visible Reflectance

Field: Slat Diffuse Visible Transmittance

The slat transmittance for hemispherically diffuse visible radiation. This value should equal “Slat Beam Visible Transmittance.”

Field: Front Side Slat Diffuse Visible Reflectance

The front-side slat reflectance for hemispherically diffuse visible radiation. This value should equal “Front Side Slat Beam Visible Reflectance.”

Field: Back Side Slat Diffuse Visible Reflectance

The back-side slat reflectance for hemispherically diffuse visible radiation. This value should equal “Back Side Slat Beam Visible Reflectance..”

Field: Slat Infrared Hemispherical Transmittance

The slat Infrared transmittance. It is zero for solid metallic, wooden or glass slats, but may be non-zero in some cases (e.g., thin plastic slats).

Field: Front Side Slat Infrared Hemispherical Emissivity

Front-side hemispherical emissivity of the slat. Approximately 0.9 for most materials. The most common exception is bare (unpainted) metal slats or slats finished with a metallic paint.

Field: Back Side Slat Infrared Hemispherical Emissivity

Back-side hemispherical emissivity of the slat. Approximately 0.9 for most materials. The most common exception is bare (unpainted) metal slats or slats finished with a metallic paint.

Field: Blind to Glass Distance

For interior and exterior blinds, the distance from the mid-plane of the blind to the adjacent glass (m). See Figure 11. Not used for between-glass blinds. As for window shades (ref: WindowMaterial:Shade) this distance is used in calculating the natural convective air flow between glass and blind that is produced by buoyancy effects.

Opening Multipliers

The following opening multipliers are defined in the same way as for window shades (see WindowMaterial:Shade, Figure 9 and Figure 10). Note that, unlike window shades, there is no input for Air-Flow Permeability; this is automatically calculated by the program from slat angle, width and separation.

Field: Blind Top Opening Multiplier

Field: Blind Bottom Opening Multiplier

Field: Blind Left-Side Opening Multiplier

Field: Blind Right-Side Opening Multiplier

Field: Minimum Slat Angle

The minimum allowed slat angle (degrees). Used only if WindowProperty:ShadingControl (for the window that incorporates this blind) varies the slat angle (i.e., the WindowProperty:ShadingControl has Type of Slat Angle Control for Blinds = ScheduledSlatAngle or BlockBeamSolar). In this case, if the program tries to select a slat angle less than Minimum Slat Angle it will be reset to Minimum Slat Angle. (Note that if the Minimum Slat Angle itself is less than the minimum allowed by Slat Width, Slat Separation and Slat Thickness, it will be reset to that minimum.)

Field: Maximum Slat Angle

The maximum allowed slat angle (degrees). Used only if WindowProperty:ShadingControl (for the window that incorporates this blind) varies the slat angle (i.e., the WindowProperty:ShadingControl has Type of Slat Angle Control for Blinds = ScheduledSlatAngle or BlockBeamSolar). In this case, if the program tries to select a slat angle greater than Maximum Slat Angle the slat angle will be reset to Maximum Slat Angle. (Note that if the Maximum Slat Angle itself is greater than the maximum allowed by Slat Width, Slat Separation and Slat Thickness, it will be reset to that maximum.)

Figure 11. (a) Side view of a window blind with horizontal slats (or top view of blind with vertical slats) showing slat geometry. The front face of a slat is shown by a heavy line. The slat angle is defined as the angle between the glazing outward normal and the slat outward normal, where the outward normal points away from the front face of the slat. (b) Slat orientations for representative slat angles. The slat angle varies from 0^O, when the front of the slat is parallel to the glazing and faces toward the outdoors, to 90^O, when the slat is perpendicular to the glazing, to 180^O, when the front of the slat is parallel to the glazing and faces toward the indoors. The minimum and maximum slat angles are determined by the slat thickness, width and separation.

WindowMaterial:Screen

This object specifies the properties of exterior window screen materials. The window screen model assumes the screen is made up of intersecting orthogonally-crossed cylinders. The surface of the cylinders is assumed to be diffusely reflecting, having the optical properties of a Lambertian surface.

The beam solar radiation transmitted through a window screen varies with sun angle and is made up of two distinct elements: a direct beam component and a reflected beam component. The direct beam transmittance component is modeled using the geometry of the screen material and the incident angle of the sun to account for shadowing of the window by the screen material. The reflected beam component is an empirical model that accounts for the inward reflection of solar beam off the screen material surface. This component is both highly directional and small in magnitude compared to the direct beam transmittance component (except at higher incident angles, for which case the magnitude of the direct beam component is small or zero and the reflected beam component, though small in absolute terms can be many times larger than the direct beam component). For this reason, the reflected beam transmittance component calculated by the model can be a. disregarded, b. treated as an additive component to direct beam transmittance (and in the same direction), or c. treated as hemispherically-diffuse transmittance based on a user input to the model.

The window screen “assembly” properties of overall beam solar reflectance and absorptance (including the screen material ‘cylinders’ and open area) also change with sun angle and are calculated based on the values of the beam solar transmittance components (direct and reflected components described above) and the physical properties of the screen material (i.e., screen material diameter, spacing, and reflectance).

Transmittance, reflectance, and absorptance of diffuse solar radiation are considered constant values and apply to both the front and back surfaces of the screen. These properties are calculated by the model as an average value by integrating the screen’s beam solar properties over a quarter hemisphere of incident radiation. Long-wave emissivity is also assumed to be the same for both sides of the screen.

There is an EnergyPlus Reference Data Set for WindowMaterial:Screen that contains properties for generic window screens. Window screens of this type can only be used on the outside surface of the window (“exterior screens”). When in place, the screen is assumed to cover all of the glazed part of the window, including dividers; it does not cover any of the window frame, if present. The plane of the screen is assumed to be parallel to the glazing.

WindowMaterial:Screen can be used to model wire mesh insect screens where the solar and visible transmission and reflection properties vary with the angle of incidence of solar radiation. For diffusing materials such as drapery and translucent roller shades it is better to use the WindowMaterial:Shade object. For slat-type shading devices like Venetian blinds, which have solar and visible transmission and reflection properties that strongly depend on slat angle and angle of incidence of solar radiation, it is better to use WindowMaterial:Blind.

Method 1:

1) Define the construction of the window without the screen, the so-called “bare” construction.

2) Reference the bare construction in the FenestrationSurface:Detailed for the window.

4) Define a WindowProperty:ShadingControl for the window in which you (a) specify that this Material:WindowScreen is the window’s shading device, and (b) specify how the screen is controlled.

Method 2:

1) Define the Construction of the window without the screen, the so-called “bare” construction.

2) Reference the bare construction in the FenestrationSurface:Detailed for the window.

4) Define another Construction, called the “shaded construction,” that includes the WindowMaterial:Screen.

5) Define a WindowProperty:ShadingControl for the window in which you (a) reference the shaded construction, and (b) specify how the screen is controlled.

Note that WindowProperty:ShadingControl has to be used with either method, even if the screen is in place at all times. You will get an error message if you try to reference a shaded construction directly from a FenestrationSurface:Detailed object.

Field: Name

Enter a unique name for the screen. This name is referenced as an outside layer in a window construction.

Field: Reflected Beam Transmittance Accounting Method

This input specifies the method used to account for screen-reflected beam solar radiation that is transmitted through the window screen (as opposed to being reflected back outside the building). Since this inward reflecting beam solar is highly directional and is not modeled in the direction of the actual reflection, the user is given the option of how to account for the directionality of this component of beam solar transmittance. Valid choices are DoNotModel, ModelAsDirectBeam (i.e., model as an additive component to direct solar beam and in the same direction), or ModelAsDiffuse (i.e., model as hemispherically-diffuse radiation). The default value is ModelAsDiffuse.

Field: Diffuse Solar Reflectance

This input specifies the solar reflectance (beam-to-diffuse) of the screen material itself (not the effective value for the overall screen “assembly” including open spaces between the screen material). The outgoing diffuse radiation is assumed to be Lambertian (distributed angularly according to Lambert’s cosine law). The solar reflectance is assumed to be the same for both sides of the screen. This value must be from 0 to less than 1.0. In the absence of better information, the input value for diffuse solar reflectance should match the input value for diffuse visible reflectance.

Field: Diffuse Visible Reflectance

This input specifies the visible reflectance (beam-to-diffuse) of the screen material itself (not the effective value for the overall screen “assembly” including open spaces between the screen material) averaged over the solar spectrum and weighted by the response of the human eye. The outgoing diffuse radiation is assumed to be Lambertian (distributed angularly according to Lambert’s cosine law). The visible reflectance is assumed to be the same for both sides of the screen. This value must be from 0 to less than 1.0.

If diffuse visible reflectance for the screen material is not available, then the following guidelines can be used to estimate this value:

Commercially-available gray scale or grayscale reflecting chart references can be purchased for improved accuracy in estimating visible reflectance (by visual comparison of screen reflected brightness with that of various known-reflectance portions of the grayscale).

Field: Thermal Hemispherical Emissivity

Long-wave emissivity ε of the screen material itself (not the effective value for the overall screen “assembly” including open spaces between the screen material). The emissivity is assumed to be the same for both sides of the screen.

For most non-metallic materials, ε is about 0.9. For metallic materials, ε is dependent on material, its surface condition, and temperature. Typical values for metallic materials range from 0.05 – 0.1 with lower values representing a more finished surface (e.g. low oxidation, polished surface). Material emissivities may be found in Table 5 from the 2005 ASHRAE Handbook of Fundamentals, page 3.9. The value for this input field must be between 0 and 1, with a default value of 0.9 if this field is left blank.

Field: Conductivity

Screen material conductivity (W/m-K). This input value must be greater than 0. The default value is 221 W/m-K (aluminum).

Field: Screen Material Spacing

The spacing, S, of the screen material (m) is the distance from the center of one strand of screen to the center of the adjacent one. The spacing of the screen material is assumed to be the same in both directions (e.g., vertical and horizontal). This input value must be greater than the non-zero screen material diameter. If the spacing is different in the two directions, use the average of the two values.

Field: Screen Material Diameter

The diameter, D, of individual strands or wires of the screen material (m). The screen material diameter is assumed to be the same in both directions (e.g., vertical and horizontal). This input value must be greater than 0 and less than the screen material spacing. If the diameter is different in the two directions, use the average of the two values.

Field: Screen to Glass Distance

Distance from the window screen to the adjacent glass surface (m). If the screen is not flat, the average screen to glass distance should be used. The screen-to-glass distance is used in calculating the natural convective air flow between the glass and the screen produced by buoyancy effects. This input value must be from 0.001 m to 1 m, with a default value of 0.025 m if this field is left blank.

Field: Top Opening Multiplier

Effective area for air flow at the top of the screen divided by the horizontal area between the glass and screen (see the same field for the Material:WindowShade object for additional description). The opening multiplier fields can be used to simulate a shading material that is offset from the window frame. Since window screens are typically installed against the window frame, the default value is equal to 0.This input value can range from 0 to 1.

Field: Bottom Opening Multiplier

Effective area for air flow at the bottom of the screen divided the horizontal area between the glass and screen (see the same field for the Material:WindowShade object for additional description). The opening multiplier fields can be used to simulate a shading material that is offset from the window frame. Since window screens are typically installed against the window frame, the default value is equal to 0. This input value can range from 0 to 1.

Field: Left-Side Opening Multiplier

Effective area for air flow at the left side of the screen divided the vertical area between the glass and screen (see the same field for the Material:WindowShade object for additional description). The opening multiplier fields can be used to simulate a shading material that is offset from the window frame. Since window screens are typically installed against the window frame, the default value is equal to 0. This input value can range from 0 to 1.

Field: Right-Side Opening Multiplier

Effective area for air flow at the right side of the screen divided the vertical area between the glass and screen (see the same field for the Material:WindowShade object for additional description). The opening multiplier fields can be used to simulate a shading material that is offset from the window frame. Since window screens are typically installed against the window frame, the default value is equal to 0. This input value can range from 0 to 1.

Field: Angle of Resolution for Screen Transmittance Output Map

Angle of resolution, in degrees, for the overall screen beam transmittance (direct and reflected) output map. The comma-separated variable file eplusscreen.csv (Ref. OutputDetailsandExamples.pdf) will contain the direct beam and reflected beam solar radiation that is transmitted through the window screen as a function of incident sun angle (0 to 90 degrees relative solar azimuth and 0 to 90 degrees relative solar altitude) in sun angle increments specified by this input field. The default value is 0, which means no transmittance map is generated. Other valid choice inputs are 1, 2, 3 and 5 degrees.

An IDF example for this object, along with Construction and WindowProperty:ShadingControl objects, is shown below:

Material:RoofVegetation

This definition must be used in order to simulate the green roof (ecoroof) model. The material becomes the outside layer in a green roof construction (see example below). In the initial release of the green roof model, only one material may be used as a green roof layer though, of course, several constructions using that material may be used. In addition, the model has only been tested with the ConductionTransferFunction solution algorithm – a warning will be issued for other solution algorithm choices.

Field: Name

This field is a unique reference name that the user assigns to a particular ecoroof material. This name can then be referred to by other input data.

Field: Height of Plants

This field defines the height of plants in units of meters. This field is limited to values in the range 0.005 < Height < 1.00 m. Default is .2 m.

Field: Leaf Area Index

This is the projected leaf area per unit area of soil surface. This field is dimensionless and is limited to values in the range of 0.001 < LAI < 5.0. Default is 1.0.

Field: Leaf Reflectivity

This field represents the fraction of incident solar radiation that is reflected by the individual leaf surfaces (albedo). Solar radiation includes the visible spectrum as well as infrared and ultraviolet wavelengths. Values for this field must be between 0.05 and 0.5. Default is .22. Typical values are .18 to .25.

Field: Leaf Emissivity

This field is the ratio of thermal radiation emitted from leaf surfaces to that emitted by an ideal black body at the same temperature. This parameter is used when calculating the long wavelength radiant exchange at the leaf surfaces. Values for this field must be between 0.8 and 1.0 (with 1.0 representing “black body” conditions). Default is .95.

Field: Minimum Stomatal Resistance

This field represents the resistance of the plants to moisture transport. It has units of s/m. Plants with low values of stomatal resistance will result in higher evapotranspiration rates than plants with high resistance. Values for this field must be in the range of 50.0 to 300.0. Default is 180.

Field: Soil Layer Name

This field is a unique reference name that the user assigns to the soil layer for a particular ecoroof. This name can then be referred to by other input data. Default is Green Roof Soil.

Field: Roughness

This alpha field defines the relative roughness of a particular material layer. This parameter only influences the convection coefficients, more specifically the exterior convection coefficient. A keyword is expected in this field with the options being “VeryRough”, “Rough”, “MediumRough”, “MediumSmooth”, “Smooth”, and “VerySmooth” in order of roughest to smoothest options. Default is MediumRough.

Field: Thickness

This field characterizes the thickness of the material layer in meters. This should be the dimension of the layer in the direction perpendicular to the main path of heat conduction. This value must be a positive. Depths of .15m (6 inches) and .30m (12 inches) are common. Default if this field is left blank is .1. Maximum is .7m. Must be greater than .05 m.

Field: Conductivity of Dry Soil

This field is used to enter the thermal conductivity of the material layer. Units for this parameter are W/(m-K). Thermal conductivity must be greater than zero. Typical soils have values from .3 to .5. Minimum is .2 (specified in IDD). Default is .35 and maximum (in IDD) is 1.5.

Field: Density of Dry Soil

This field is used to enter the density of the material layer in units of kg/m³. Density must be a positive quantity. Typeical soils range from 400 to 1000 (dry to wet). Minimum is 300, maximum is 2000 and default if field is left blank is 1100.

Field: Specific Heat of Dry Soil

Field: Thermal Absorptance

Field: Solar Absorptance

Field: Visible Absorptance

Field: Saturation Volumetric Moisture Content of the Soil Layer

The field allows for user input of the saturation moisture content of the soil layer. Maximum moisture content is typically less than .5. Range is (.1,.5] with the default being .3.

Field: Residual Volumetric Moisture Content of the Soil Layer

The field allows for user input of the residual moisture content of the soil layer. Default is .01, range is [.01,.1].

Field: Initial Volumetric Moisture Content of the Soil Layer

The field allows for user input of the initial moisture content of the soil layer. Range is (.05, .5] with the defaulte being .1.

Field: Moisture Diffusion Calculation Method

Simple is the original Ecoroof model - based on a constant diffusion of moisture through the soil. This model starts with the soil in two layers. Every time the soil properties update is called, it will look at the two soils moisture layers and asses which layer has more moisture in it. It then takes moisture from the higher moisture layer and redistributes it to the lower moisture layer at a constant rate.

Advanced is the later Ecoroof model. If you use it, you will need to increase your number of timesteps in hour for the simulation with a recommended value of 20. This moisture transport model is based on a project which looked at the way moisture transports through soil. It uses a finite difference method to divide the soil into layers (nodes). It redistributes the soil moisture according the model described in:

Marcel G Schaap and Martinus Th. van Genuchten, 2006, 'A modified Maulem-van Genuchten Formulation for Improved Description of the Hydraulic Conductivity Near Saturation’, Vadose Zone Journal 5 (1), p 27-34.

MaterialProperty:GlazingSpectralData

With the MaterialProperty:GlazingSpectralData object, you can specify the wavelength-by-wavelength transmittance and reflectance properties of a glass material. To determine the overall optical properties of a glazing system (solar and visible transmittance and solar absorptance vs. angle of incidence) EnergyPlus first calculates transmittance and absorptance vs. angle of incidence for each wavelength. This is then weighted by a standard solar spectrum to get the solar transmittance and absorptance vs. angle of incidence (for use in the solar heat gain calculations), and further weighted by the response of the human eye to get the visible transmittance vs. angle of incidence (for use in the daylighting calculation).

MaterialProperty:GlazingSpectralData should be used for multi-pane windows when one or more of the glass layers is spectrally selective, i.e., the transmittance depends strongly on wavelength. An example is glass with a coating that gives high transmittance in the daylight part of the solar spectrum (roughly 0.4 to 0.7 microns) and low transmittance at longer wavelengths, thus providing better solar heat gain control than uncoated glass. If spectral data is not used in case, the overall optical properties of the glazing system that EnergyPlus calculates will not be correct.

You can input up to 450 sets of values for wavelengths covering the solar spectrum. Each set consists of {wavelength (microns), transmittance, front reflectance, back reflectance}

Spectral data of this kind are routinely measured by glass manufacturers. Data sets for over 800 commercially available products are contained in an Optical Data Library maintained by the Windows Group at Lawrence Berkeley National Laboratory. This library can be downloaded from http://windows.lbl.gov/. You will have to edit entries from this library to put them in the format required by the EnergyPlus WindowGlassSpectralData object.

An alternative to using the MaterialProperty:GlazingSpectralData object is to run the WINDOW 5 window analysis program. This program has built-in access to the Optical Data Library and let’s you easily create customized, multi-layer glazing systems that can be exported for use in EnergyPlus. For more details, see “StormWindow”.

Field: Name

The name of the spectral data set. It is referenced by WindowMaterial:Glazing when Optical Data Type = Spectral.

Fields 1-4 (repeated up to 450 times)

Sets of values for wavelengths covering the solar spectrum (from about 0.25 to 2.5 microns [10^-6 m]). Each set consists of

The wavelength values must be in ascending order. The transmittance and reflectance values are at normal incidence. “Front reflectance” is the reflectance for radiation striking the glass from the outside, i.e., from the side opposite the zone in which the window is defined. “Back reflectance” is the reflectance for radiation striking the glass from the inside, i.e., from the zone in which the window is defined. Therefore, for exterior windows, “front” is the side closest to the outdoors and “back” is the side closest to the zone in which the window is defined. For interior windows, “front” is the side closest to the adjacent zone and “back” is the side closest to the zone in which the window is defined.

Construction

For walls, roofs, floors, windows, and doors, constructions are “built” from the included materials. Each layer of the construction is a material name listed in order from “outside” to “inside”. Up to ten layers (eight for windows) may be specified (one of the few limitations in EnergyPlus!). “Outside” is the layer furthest away from the Zone air (not necessarily the outside environment). “Inside” is the layer next to the Zone air. In the example floor below, for example, the outside layer is the acoustic tile below the floor, the next layer is the air space above the tile, and the inside layer is the concrete floor deck.

Window constructions are similarly built up from items in the Window Materials set using similar layers.. See Figure 15. Illustration for material ordering in windows, which shows the case where an interior shading layer such as a blind is present. The gap between the inside glass layer (layer #3) and the interior shading layer is not entered. Similarly, for an exterior shading layer, the gap between the outside glass layer and the shading layer is not entered.

However, for a between-glass shading device the gaps on either side of the shading layer must be entered and they must have the same gas type. In addition, the gap widths with and without the between-glass shading layer must be consistent (see Figure 16).

A maximum of four glass layers and one shading layer is allowed. A gas layer must always separate adjacent glass layers in a multi-pane glazing without a between-glass shading layer.

Figure 16. Window construction with and without a between-glass shading layer. Shown are gap widths g, g₁ and g₂, and shading layer width, w. An error will result if g₁+g₂+w is not equal to g, where w is zero for a blind and greater than zero for a shade.

Outside and inside air film resistances are never given as part of a construction definitions since they are calculated during the EnergyPlus simulation. Note also that constructions are assumed to be one-dimensional in a direction perpendicular to the surface.

Field: Name

This field is a user specified name that will be used as a reference by other input syntax. For example, a heat transfer surface (ref: Building Surfaces) requires a construction name to define what the make-up of the wall is. This name must be identical to one of the Construction definitions in the input data file.

Field: Outside Layer

Each construction must have at least one layer. This field defines the material name associated with the layer on the outside of the construction—outside referring to the side that is not exposed to the zone but rather the opposite side environment, whether this is the outdoor environment or another zone. Material layers are defined based on their thermal properties elsewhere in the input file (ref: Material and Material Properties and Materials for Glass Windows and Doors). As noted above, the outside layer should NOT be a film coefficient since EnergyPlus will calculate outside convection and radiation heat transfer more precisely.

Field(s) 2-10: Layers

The next fields are optional and the number of them showing up in a particular Construction definition depends solely on the number of material layers present in that construction. The data expected is identical to the outside layer field (see previous field description). The order of the remaining layers is important and should be listed in order of occurrence from the one just inside the outside layer until the inside layer is reached. As noted above, the inside layer should NOT be a film coefficient since EnergyPlus will calculate inside convection and radiation heat transfer more precisely.

Site:GroundTemperature:FCfactorMethod

Field: Month Temperature(s) – 12 fields in all

Each numeric field is the monthly ground temperature (degrees Celsius) used for the indicated month (January=1^st field, February=2^nd field, etc.)

Constructions - Modeling Underground Walls and Ground Floors Defined with C and F Factors for Building Energy Code Compliance

Building energy code and standards like ASHRAE 90.1, 90.2 and California Title 24 require the underground wall constructions and slabs-on-grade or underground floors not to exceed certain maximum values of C-factor and F-factor, which do not specify detailed layer-by-layer materials for the constructions.

A simplified approach is introduced to create equivalent constructions and model the ground heat transfer through underground walls and ground floors for the building energy code compliance calculations. The approach is to create constructions based on the user defined C or F factor with two layers: one concrete layer (0.15 m thick) with thermal mass, and one fictitious insulation layer with no thermal mass. Three new objects were created for such purpose: Construction:CfactorUndergroundWall, Construction:FfactorGroundFloor, and Site:GroundTemperature:FCfactorMethod. Details of the approach are described in the Engineering Reference document. The wall and floor construction objects are described in this section; the ground temperature object is described with the other ground temperature objects.

When a underground wall or ground floor surface (BuildingSurface:Detailed, Floor:Detailed, and Wall:Detailed) references one of the two construction objects, its field ‘Outside Boundary Condition’ needs to be set to GroundFCfactorMethod. For simple (rectangular) wall and floor objects, the outside boundary condition is inferred from the construction type.

The Site:GroundTemperature:FCfactorMethod is described in the section for ground temperatures, the following section describes the two new construction objects.

Construction:CfactorUndergroundWall

This input object differs from the usual wall construction object in that it describes an entire construction rather than individual layers. This object is used when only the wall height (depth to the ground) and the C-factor are available. This object accesses a model that creates an equivalent layer-by-layer construction for the underground wall to approximate the heat transfer through the wall considering the thermal mass of the earth soil.

This object is referenced by underground wall surfaces with their fields ‘Outside Boundary Condition’ set to GroundFCfactorMethod.

Field: Name

Field: C-Factor

C-Factor is the time rate of steady-state heat flow through unit area of the construction, induced by a unit temperature difference between the body surfaces. The C-Factor unit is W/m²·K. The C-factor does not include soil or air films. ASHRAE Standard 90.1 and California Title 24 specify maximum C-factors for underground walls depending on space types and climate zones.

Field: Height

This field describes the height of the underground wall, i.e. the depth to the ground surface. The unit is meters.

Construction:FfactorGroundFloor

This input object differs from the usual ground floor construction object in that it describes an entire construction rather than individual layers. This object is used when only the floor area, exposed perimeter, and the F-factor are available. This object accesses a model that creates an equivalent layer-by-layer construction for the slab-on-grade or underground floor to approximate the heat transfer through the floor considering the thermal mass of the earth soil.

This object is referenced by slab-on-grade or underground floor surfaces with their fields ‘Outside Boundary Condition’ set to GroundFCfactorMethod.

Field: Name

Field: F-Factor

F-Factor represents the heat transfer through the floor, induced by a unit temperature difference between the outside and inside air temperature, on the per linear length of the exposed perimeter of the floor. The unit for this input is W/m·K. ASHRAE Standard 90.1 and California Title 24 specify maximum F-factors for slab-on-grade or underground floors depending on space types and climate zones.

Field: Area

This field describes the area (in square meters) of the slab-on-grade or underground floor.

Field: PerimeterExposed

This field describes the exposed (direct contact with ambient air) perimeter (in meters) of the slab-on-grade or underground floor.

Construction:UseHBAlgorithmCondFDDetailed

If the ConductionFiniteDifferenceSimplified solution algorithm is being used and there is a surface (that is, construction) that should be simulated with the detailed node arrangement, it should be specified with this object. If you have similar constructions and you want some to be using the detailed algorithm and some to use the simplified (two-node) algorithm, you must create different constructions for each case.

Field: Construction Name

This is the name of the construction that will be simulated with the detailed algorithm. If there are other surfaces that use the same construction, this one should be given a different and unique name.

Construction:InternalSource

In some cases such as radiant systems, a construction will actually have resistance wires or hydronic tubing embedded within the construction. Heat is then either added or removed from this building element to provide heating or cooling to the zone in question. In the case of building-integrated photovoltaics, the energy removed in the form of electricity will form a sink. It is possible to enter such constructions into EnergyPlus with the syntax described below. The definition is similar to the Construction definition with a few additions related to radiant or other systems that will lead to source/sink terms. The internal source capability is available with both the ConductionTransferFunction and ConductionFiniteDifference solution algorithms. The only difference is that the two dimensional pipe arrangements are not available to ConductionFiniteDifference. Those fields are ignored in that implementation.

Field: Name

Field: Source Present After Layer Number

This field is an integer that relates the location of the heat source or sink. The integer refers to the list of material layers that follow later in the syntax and determines the layer after which the source is present. If a source is embedded within a single homogenous layer (such as concrete), that layer should be split into two layers and the source added between them. For example, a value of “2” in this field tells EnergyPlus that the source is located between the second and third material layers listed later in the construction description (see layer fields below).

Field: Temperature Calculation Requested After Layer Number

The nature of this field is similar to the source interface parameter (see previous field) in that it is an integer, refers to the list of material layers that follow, and defines a location after the layer number identified by the user-defined number. In this case, the user is specifying the location for a separate temperature calculation rather than the location of the heat source/sink. This feature is intended to allow users to calculate a temperature within the construction. This might be important in a radiant cooling system where condensation could be a problem. This temperature calculation can assist users in making that determination in absence of a full heat and mass balance calculation.

Field: Dimensions for the CTF Calculation

This field is also an integer and refers to the detail level of the calculation. A value of “1” states that the user is only interested in a one-dimensional calculation. This is appropriate for electric resistance heating and for hydronic heating (when boiler/hot water heater performance is not affected by return and supply water temperatures). A value of “2” will trigger a two-dimensional solution for this surface only. This may be necessary for hydronic radiant cooling situations since chiller performance is affected by the water temperatures provided.

A few things should be noted about requesting two-dimensional solutions. First, the calculation of the conduction transfer functions (CTF) is fairly intensive and will require a significant amount of computing time. Second, the solution regime is two-dimensional internally but it has a one-dimensional boundary condition imposed at the inside and outside surface (i.e., surface temperatures are still isothermal is if the surface was one-dimensional).

Field: Tube Spacing

This field defines how far apart in meters the hydronic tubing or electrical resistance wires are spaced in the direction perpendicular to the main direction of heat transfer. Note that this parameter is only used for two-dimensional solutions (see previous field).

Field: Outside Layer

Each construction must have at least one layer. This field defines the material name associated with the layer on the outside of this construction—outside referring to the side that is not exposed to the zone but rather the opposite side environment, whether this is the outdoor environment or another zone. Material layers are defined based on their thermal properties elsewhere in the input file (ref: Material and Material Properties and Materials for Glass Windows and Doors). As noted above, the outside layer should NOT be a film coefficient since EnergyPlus will calculate convection and radiation heat transfer more precisely.

Field(s) 2-10: Layers

The next fields are optional and the number of them showing up in a particular Construction definition depends solely on the number of material layers present in that particular construction. The data expected is identical to the outside layer field (see previous field description). The order of the remaining layers is important and should be listed in order of occurrence from the one just inside the outside layer until the inside layer is reached. As noted above, the inside layer should NOT be a film coefficient since EnergyPlus will calculate convection and radiation heat transfer more precisely.

Composite Wall Constructions

Standard constructions in EnergyPlus are built with the materials and layers described earlier. However, some configurations will not be adequately represented by using this approach. The Reference Data Set CompositeWallConstructions.idf contains constructions and associated materials for a set of composite walls. These are walls—such as stud walls—that have complicated heat-flow paths so that the conduction is two- or three-dimensional. Thermal bridges are one of the common terms for these complicated heat-flow paths; this dataset will help you represent these in EnergyPlus.

The materials here are not real materials but are “equivalent” materials obtained from finite-difference modeling.[4] EnergyPlus will calculate conduction transfer functions using these materials. The heat transfer based on these conduction transfer functions will then be very close to what would be calculated with a two- or three-dimensional heat transfer calculation.

For stud walls, using these composite constructions will give more accurate heat flow than you would get by manually dividing the wall into a stud section and a non-stud section.

If your wall’s exterior or interior roughness or thermal, solar or visible absorptances are different from those in the data set, you can make the appropriate changes to the first material (the outside layer) or the third material (the inside layer). None of the other values should be changed.

Construction:WindowDataFile

The WINDOW 5 program, which does a thermal and optical analysis of a window under different design conditions, writes a data file (“Window5 data file”) containing a description of the window that was analyzed. The Construction:WindowDataFile object allows a window to be read in from the Window5 data file—see “Importing Windows from WINDOW 5.” For information on adding a shading device to the window see “WindowProperty:ShadingControl.”

Field: Name

This is the name of a window on the Window5 data file. An error will result if EnergyPlus cannot find a window of this name on the file, or if the file, called Window5DataFile.dat, is not present. The exact location of the Windows5DataFile.dat file should be specified in the File Name field. For details on what is done with the data if a matching window is found on the file see “Importing Windows from WINDOW 5.”

Field: File Name

This is the file name of the Window5 data file that contains the Window referenced in the previous field. You must specify this file name completely, including path, but it must be 60 characters or less. A relative path or a simple file name will not work with version 6.0 or later when using EP-Launch due to the use of temporary directories as part of the execution of EnergyPlus. If using RunEPlus.bat to run EnergyPlus from the command line, a relative path or a simple file name may work if RunEPlus.bat is run from the folder that contains EnergyPlus.exe.

An example showing use of specific data file name and complete path location follows:

Construction Element Outputs

An optional report (contained in eplusout.eio) gives calculational elements for the materials and constructions used in the input. These reports are explained fully in the Output Details and Examples document.

Group – Thermal Zone Description/Geometry

Without thermal zones and surfaces, the building can’t be simulated. This group of objects (Zone, BuildingSurface) describes the thermal zone characteristics as well as the details of each surface to be modeled. Included here are shading surfaces.

Zone

This element sets up the parameters to simulate each thermal zone of the building.

Field: Direction of Relative North

The Zone North Axis is specified relative to the Building North Axis. This value is specified in degrees (clockwise is positive). For more information, see the figure below as well as the description under “GlobalGeometryRules”.

Field(s): (X,Y,Z) Origin

The X,Y,Z coordinates of a zone origin can be specified, for convenience in vertice entry. Depending on the values in “GlobalGeometryRules” (see description later in this section), these will be used to completely specify the building coordinates in “world coordinate” or not. Zone Origin coordinates are specified relative to the Building Origin (which always 0,0,0). The following figure illustrates the use of Zone North Axis as well as Zone Origin values.

Field: Type

Field: Multiplier

Zone Multiplier is designed as a “multiplier” for zone loads. It takes the calculated load for the inputted zone and multiplies it and sends the multiplied load to the attached system to meet the demand. The system will have to be specified to meet the entire multiplied zone load and will report the amount of the load it can meet in the Zone/Sys Sensible Heating or Cooling Energy/Rate report variable. The default is 1.

Field: Ceiling Height

Zone ceiling height is used in several areas within EnergyPlus. Energyplus automatically calculates the zone ceiling height (m) from the average height of the zone. If this field is 0.0, negative or autocalculate, then the calculated zone ceiling height will be used in subsequent calculations. If this field is positive, then the calculated zone ceiling height will not be used -- the number entered here will be used as the zone ceiling height. If this number differs significantly from the calculated ceiling height, then a warning message will be issued. If a zone ceiling height is entered, but no Volume is entered, then the floor area (if there is one) times the zone ceiling height will be used as the volume.

Note that the Zone Ceiling Height is the distance from the Floor to the Ceiling in the Zone, not an absolute height from the ground.

Field: Volume

Zone volume is used in several areas within EnergyPlus. EnergyPlus automatically calculates the zone volume (m³) from the zone geometry given by the surfaces that belong to the zone. If this field is 0.0, negative or autocalculate, then the calculated zone volume will be used in subsequent calculations. If this field is positive, then it will be used as the zone volume. If this number differs significantly from the calculated zone volume a warning message will be issued. For autocalculate to work properly, the zone must be enclosed by the entered walls. Note that indicating the volume to be calculated but entering a positive ceiling height in the previous field will cause the volume to be calculated as the floor area (if > 0) times the entered ceiling height; else the volume will be calculated from the described surfaces. If this field is positive, any ceiling height positive value will not be used in volume calculations.

Field: Floor Area

Zone floor area is used in many places within EnergyPlus. EnergyPlus automatically calculates the zone floor area (m²) from the zone geometry given by the surfaces that belong to the zone. If this field is 0.0, negative or autocalculate, then the calculated zone floor area will be used in subsequent calculations. If this field is positive, then it will be used as the zone floor area. If this number differs significantly from the calculated zone floor area a warning message will be issued.

Field: Zone Inside Convection Algorithm

The Zone Inside Convection Algorithm field is optional. This field specifies the convection model to be used for the inside face of heat transfer surfaes associated with this zone. The choices are: Simple (constant natural convection - ASHRAE), Detailed (variable natural convection based on temperature difference - ASHRAE), CeilingDiffuser (ACH based forced and mixed convection correlations for ceiling diffuser configuration with simple natural convection limit), AdaptiveConvectionAlgorithm (complex arrangement of various models that adapt to various zone conditions and can be customized) and TrombeWall (variable natural convection in an enclosed rectangular cavity). See the Inside Convection Algorithm object for further descriptions of the available models.

If omitted or blank, the algorithm specified in the SurfaceConvectionAlgorithm:Inside object is the default.

Field: Zone Outside Convection Algorithm

The Zone Outside Convection Algorithm field is optional. This field specifies the convection model to be used for the outside face of heat transfer surfaces associated with this zone. The choices are: SimpleCombined, TARP, DOE-2, MoWiTT, and AdaptiveConvectionAlgorithm. The simple convection model applies heat transfer coefficients depending on the roughness and windspeed. This is a combined heat transfer coefficient that includes radiation to sky, ground, and air. The correlation is based on Figure 1, Page 25.1 (Thermal and Water Vapor Transmission Data), 2001 ASHRAE Handbook of Fundamentals.

The other convection models apply heat transfer coefficients depending on the roughness, windspeed, and terrain of the building’s location. These are convection only heat transfer coefficients; radiation heat transfer coefficients are calculated automatically by the program. The TARP algorithm was developed for the TARP software and combines natural and wind-driven convection correlations from laboratory measurements on flat plates. The DOE-2 and MoWiTT were derived from field measurements. The AdaptiveConvectionAlgorithm model is an dynamic algorithm that organizes a large number of different convection models and automatically selects the one that best applies. The adaptive convection algorithm can also be customized using the SurfaceConvectionAlgorithm:Outside:AdaptiveModelSelections input object. All algorithms are described more fully in the Engineering Reference.

If omitted or blank, the algorithm specified in the SurfaceConvectionAlgorithm:Outside object is the default.

Field: Part of Total Floor Area

This optional field defaults to Yes if not specified. The field is used to show when a zone is not part of the Total Floor Area as shown in the Annual Building Utility Performance Summary tables. Specifically, when No is specified, the area is excluded from both the conditioned floor area and the total floor area in the Building Area sub table and the Normalized Metrics sub tables.

Zone Outputs

Each zone command produces zone outputs that echo the input fields above. However, the values to be used for the Zone Ceiling Height and Volume will be displayed if the entered fields are negative or zero. Details on this report are shown in the Output Details and Examples document.

In addition to the invariant outputs for the zone, atmospheric temperature and wind speed due to zone centroid heights are calculated. Rationale and further details on these values is shown in the Weather Station and Site Atmospheric Variation objects. These are described in the Group -- Location – Climate – Weather File Access.

Zone Outdoor Dry Bulb [C]

The outdoor air dry-bulb temperature calculated at the height above ground of the zone centroid.

Zone Outdoor Wet Bulb [C]

The outdoor air wet-bulb temperature calculated at the height above ground of the zone centroid.

Zone Outdoor Wind Speed [m/s]

The outdoor wind speed calculated at the height above ground of the zone centroid.

Zone Thermal Output(s)

In addition to the canned Surface reports (view the Reports section later in this document) and surface variables (above), the following variables are available for all zones:

These two variable outputs are/should be identical. However, note that they can be reported at different time intervals. “Zone Mean Air Temperature” is only available on the Zone/HB timestep (Number of Timesteps per Hour) whereas “Zone/Sys Air Temperature” can be reported at the HVAC timestep (which can vary).

Zone Mean Air Temperature [C]

From the code definition, the zone mean air temperature is the average temperature of the air temperatures at the system timestep. Remember that the zone heat balance represents a “well stirred” model for a zone, therefore there is only one mean air temperature to represent the air temperature for the zone.

Zone/Sys Air Temperature[C]

This is very similar to the mean air temperature in the last field. The “well stirred” model for the zone is the basis, but this temperature is also available at the “detailed” system timestep.

Zone/Sys Air Temperature at Thermostat [C]

Zone Mean Radiant Temperature [C]

The Mean Radiant Temperature (MRT) in degrees Celsius of a space is a measure of the combined effects of temperatures of surfaces within that space. Specifically it is the surface area × emissivity weighted average of the zone inside surface temperatures (ref. Surface Inside Temperature), where emissivity is the Thermal Absorptance of the inside material layer of each surface.

Zone Operative Temperature [C]

Zone Operative Temperature (OT) is the average of the Zone Mean Air Temperature (MAT) and Zone Mean Radiant Temperature (MRT), OT = 0.5*MAT + 0.5*MRT. This report variable is not affected by the type of thermostat controls in the zone, and does not include the direct effect of high temperature radiant systems. See also Zone Thermostat Operative Temperature.

Zone Air Balance Internal Convective Gains Rate [W]

The Zone Air Balance Internal Convective Gains Rate is the sum, in watts, of heat transferred to the zone air from all types of internal gains, including people, lights, equipment etc. This and the following provide results on the load components of the zone air heat balance. This field is not multiplied by zone or group multipliers.

Zone Air Balance Surface Convection Rate [W]

The Zone Air Balance Surface Convection Rate is the sum, in watts, of heat transferred to the zone air from all the surfaces. This field is not multiplied by zone or group multipliers.

Zone Air Balance Interzone Air Transfer Rate [W]

The Zone Air Balance Interzone Air Transfer Rate is the sum, in watts, of heat transferred to the zone air from all the transfers of air from other thermal zones. This field is not multiplied by zone or group multipliers.

Zone Air Balance Outdoor Air Transfer Rate [W]

The Zone Air Balance Outdoor Air Transfer Rate is the sum, in watts, of heat transferred to the zone air from all the transfers of air from the out side, such as infiltration. This field is not multiplied by zone or group multipliers.

Zone Air Balance System Air Transfer Rate [W]

The Zone Air Balance System Air Transfer Rate is the sum, in watts, of heat transferred to the zone air by HVAC air systems. This field is not multiplied by zone or group multipliers.

Zone Air Balance Air Energy Storage Rate [W]

The Zone Air Balance Air Energy Storage Rate is the heat stored, in watts, in the zone air as result of zone air temperature changing from one timestep to the next. This field is not multiplied by zone or group multipliers.

Zone Air Balance Deviation Rate [W]

The Zone Air Balance Deviation Rate is the imbalance, in watts, in the energy balance for zone air. The value should be near zero but will become non-zero if zone conditions are changing rapidly or erratically. This field is not multiplied by zone or group multipliers. (This report variable is only generated if the user has set a computer system environment variable DisplayAdvancedReportVariables equal to “yes”.)

Zone/Sys Sensible Heating Energy [J]

This report variable represents the sensible heating energy in Joules that is actually supplied by the system to that zone for the timestep reported. This is the sensible heating rate multiplied by the simulation timestep. This is calculated and reported from the Correct step in the Zone Predictor-Corrector module. . This field is not multiplied by zone or group multipliers.

Zone/Sys Sensible Cooling Energy [J]

This report variable represents the sensible cooling energy in Joules that is actually supplied by the system to that zone for the timestep reported. This is the sensible cooling rate multiplied by the simulation timestep. This is calculated and reported from the Correct step in the Zone Predictor-Corrector module. This field is not multiplied by zone or group multipliers.

Zone/Sys Sensible Heating Rate [W]

This report variable represents the sensible heating rate in Watts that is actually supplied by the system to that zone for the timestep reported. This is calculated and reported from the Correct step in the Zone Predictor-Corrector module. This field is not multiplied by zone or group multipliers.

Zone/Sys Sensible Cooling Rate [W]

This report variable represents the sensible cooling rate in Watts that is actually supplied by the system to that zone for the timestep reported. This is calculated and reported from the Correct step in the Zone Predictor-Corrector module. This field is not multiplied by zone or group multipliers.

Zone Air Humidity Ratio []

This report variable represents the air humidity ratio after the correct step for each zone. The humidity ratio is the mass of water vapor to the mass of dry air contained in the zone in (kg water/kg air) and is unitless.

Zone Air Relative Humidity [%]

This report variable represents the air relative humidity after the correct step for each zone. The relative humidity is in percent and uses the Zone Air Temperature, the Zone Air Humidity Ratio and the Outside Barometric Pressure for calculation.

Zone Total Internal Radiant Heat Gain Rate [W]

Zone Total Internal Radiant Heat Gain [J]

These report variables represent the sum of radiant gains from specific internal sources (e.g. equipment) throughout the zone in Watts (for rate) or joules. This includes radiant gain from People, Lights, Electric Equipment, Gas Equipment, Other Equipment, Hot Water Equipment, and Steam Equipment.

Zone-Total Internal Visible Heat Gain Rate [W]

Zone-Total Internal Visible Heat Gain [J]

These report variables expresse the sum of heat gain in Watts (for rate) or joules that is the calculated short wavelength radiation gain from lights in the zones. This calculation uses the total energy from lights and the fraction visible to realize this value, summed over the zones in the simulation.

Zone Total Internal Convective Heat Gain Rate [W]

Zone Total Internal Convective Heat Gain [J]

These report variables represent the sum of convective gains from specific sources (e.g. equipment) throughout the zone in Watts (for rate) or joules. This includes convective gain from People, Lights, Electric Equipment, Gas Equipment, Other Equipment, Hot Water Equipment, and Steam Equipment.

Zone Total Internal Latent Gain Rate [W]

Zone Total Internal Latent Gain [J]

These report variables represent the sum of latent gains from specific internal sources (e.g. equipment) throughout the zone in Watts (for rate) or joules. This includes latent gain from People, Electric Equipment, Gas Equipment, Other Equipment, Hot Water Equipment, and Steam Equipment.

Zone Total Internal Total Heat Gain Rate [W]

Zone Total Internal Total Heat Gain [J]

These report variables represent the sum of all heat gains throughout the zone in Watts (for rate) or joules. This includes all heat gains from People, Lights, Electric Equipment, Gas Equipment, Other Equipment, Hot Water Equipment, and Steam Equipment.

ZoneList

The ZoneList object defines a list of Zone objects. It is primarily used with the ZoneGroup object to provide a generalized way for doing "Floor Multipliers". (See the ZoneGroup description below.) The associated ZoneList output variables also provide a way to aggregate and organize zone loads.

Zone lists are not exclusive. A zone can be referenced be more than one ZoneList object.

Field: Zone List Name

Field: Zone 1 – 20 Name

Reference to a Zone object. This field is extensible; for greater than 20 zones, edit the IDD to add more Zone Name fields.

ZoneList Outputs

All ZoneList variables are the sum of the corresponding Zone variables. Zone Multiplier fields in the Zone objects are also taken into account.

ZoneGroup

The ZoneGroup object adds a multiplier to a ZoneList. This can be used to reduce the amount of input necessary for simulating repetitive structures, such as the identical floors of a multi-story building. To create a "Floor Multiplier", use the ZoneList object to organize several zones into a typical floor. Then use the Zone List Multiplier field in the ZoneGroup object to multiply the system load for the zones in the list will also be multiplied. Zones with a Multiplier field greater than one in the Zone object are effectively double-multiplied.

Tips for Multi-Story Simulations:

n For floors that are multiplied, connect exterior boundary conditions of the floor to the ceiling and vice versa.

n Since exterior convection coefficients vary with elevation, locate the typical middle floor zones midheight between the lowest and highest middle floors to be modeled.

n Shading must be identical for all multiplied floors or less accurate results may be obtained by using the zone list multiplier.

ZoneGroup and ZoneList can also be used to simulate other repetitive cases, such as clusters of zones on the ground.

Field: Zone Group Name

Field: Zone List Name

Reference to a ZoneList object. The zones in the list constitute the zones in the group.

Field: Zone List Multiplier

ZoneGroup Outputs

All ZoneGroup variables report the associated ZoneList value multiplied by the Zone List Multiplier.

Surface(s)

Each of the preceding surfaces has “correct” geometry specifications. BuildingSurface and Fenestration surfaces (heat transfer surfaces) are used to describe the important elements of the building (walls, roofs, floors, windows, doors) that will determine the interactions of the building surfaces with the outside environment parameters and the internal space requirements. These surfaces are also used to represent “interzone” heat transfer. During specification of surfaces, several “outside” environments may be chosen:

n Ground – when the surface is in touch with the ground (e.g. slab floors)

n Outdoors – when the surface is an external surface (e.g. walls, roofs, windows directly exposed to the outdoor conditions)

n OtherSideCoefficients – when using a custom profile to describe the external conditions of the surface (advanced concept – covered in subject: SurfaceProperty:OtherSideCoefficients)

n OtherSideConditionsModel – when using specially modeled components, such as active solar systems, that cover the outside surface and modify the conditions it experiences.

n An “opposing” surface name (in the current zone) – for representing “middle” zones.

n The zone that contains the other surface that is adjactent to this surface but is not entered in input.

Shading surfaces are used to describe aspects of the site which do not directly impact the physical interactions of the environmental parameters but may significantly shade the building during specific hours of the day or time so the year (e.g. trees, bushes, mountains, nearby buildings which aren’t being simulated as part of this facility, etc.)

is used to specify the construction/material parameters and area of items within the space that are important to heat transfer calculations but not necessarily important geometrically. (For example, furniture within the space – particularly for large spaces). Internal mass can also be used for internal walls that are not needed (when FullInteriorAndExterior Solar Distribution is in effect) for solar distribution or to represent many, if not all, interior walls when solar is distributed to the floors only.

Interzone Surfaces

EnergyPlus can quite accurately simulate the surface heat exchange between two zones. However, this accuracy is not always required and using interzonal heat transfer does add to the complexity of the calculations – thus requiring more CPU time to simulate. More information about interzonal heat transfer calculations is contained in the Engineering Reference. Some simple guidelines are presented here – for three cases: adiabatic surfaces, surfaces in “middle” zones, and surfaces where heat transfer is “expected” (e.g. between a residence and an unheated, attached garage).

n Adiabatic Surfaces – These surfaces would be represented as common surfaces (between two zones) where both zones are typically the same temperature. Thus, no transfer is expected in the surface from one zone to the next. These surfaces should be described as simply internal surfaces for the zone referencing as their Outside Boundary Condition Object (see later description in individual surface objects) their own surface names.

n Surfaces in Middle Zones – Middle zones in a building can be simulated using a judicious use of surfaces and zone multipliers to effect the correct “loads” for the building. Thus, middle zone behavior can be simulated without modeling the adjacent zones. This is done by specifying a surface within the zone. For example, a middle floor zone can be modeled by making the floor the Outside Boundary Condition Object for the ceiling, and the ceiling the Outside Boundary Condition Object for the floor.

n Surfaces between Zones with differing temperatures – These zones represent the true use of interzone surfaces. In a residence that has an attached garage, the garage may be unheated/uncooled or at least not conditioned to the same degree as the residence interior. In this case, EnergyPlus can be used to accurately calculate the effects of the differently conditioned space to the other spaces.

Surface View Factors

EnergyPlus uses an area weighted approximation to calculate "view factors" between surfaces within a thermal zone. Each surface uses the total area that it can “see” among the other surfaces. The approximate view factor from this surface to each other surface is then the area of the receiving surface over the sum of areas that is visible to the sending surface.

In order to account in some limited way for the fact that certain surfaces will not see each other, several assumptions have been built into this simple view factor approximation. First, a surface cannot see itself. Second, surfaces with approximately the same azimuth (facing direction) and tilt ("same" being within a built in limit) will not see each other. This means that a window will not see the wall that it is placed on, for example. Third, floors cannot see each other. Fourth, if the surface is a floor, ceiling, roof, or internal mass, the rule for the same azimuth and tilt eliminating radiant exchange between surface is waived when the receiving surface is floor, roof, ceiling, or internal mass as long as both surfaces are not floors.

Note that this does not take into account that surfaces may be "around the corner" from each other and in reality not see each other at all. Rooms are assumed to be convex rather than concave in this method.

7. All other surfaces whose tilt or facing angle differences are greater than 10 degrees see each other.

If geometry is correct, conditions 1,3, and 7 should take care of all surfaces, but the other conditions supply common sense when the geometry is incorrect. More information about the EnergyPlus view factor calculation is contained in the Engineering Reference document.

GlobalGeometryRules

Before the surface objects are explained in detail, a description of geometric parameters used in EnergyPlus will be given. Since the input of surface vertices is common to most of the surface types, it will also be given a separate discussion.

Some flexibility is allowed in specifying surface vertices. This flexibility is embodied in the GlobalGeometryRules class/object in the input file. Note that the parameters specified in this statement are used for all surface vertice inputs – there is no further “flexibility” allowed.

In order to perform shadowing calculations, the building surfaces must be specified. EnergyPlus uses a three dimensional (3D) Cartesian coordinate system for surface vertex specification. This Right Hand coordinate system has the X-axis pointing east, the Y-axis pointing north, and the Z-axis pointing up. See figure below.

Field: Starting Vertex Position

The shadowing algorithms in EnergyPlus rely on surfaces having vertices in a certain order and positional structure. Thus, the surface translator needs to know the starting point for each surface entry. The choices are: UpperLeftCorner, LowerLeftCorner , UpperRightCorner, or LowerRightCorner. Since most surfaces will be 4 sided, the convention will specify this position as though each surface were 4 sided. Extrapolate 3 sided figures to this convention. For 5 and more sided figures, again, try to extrapolate the best “corner” starting position.

Field: Vertex Entry Direction

Surfaces are always specified as being viewed from the outside of the zone to which they belong. (Shading surfaces are specified slightly differently and are discussed under the particular types). EnergyPlus needs to know whether the surfaces are being specified in counterclockwise or clockwise order (from the Starting Vertex Position). EnergyPlus uses this to determine the outward facing normal for the surface (which is the facing angle of the surface – very important in shading and shadowing calculations.

Field: Coordinate System

Vertices can be specified in two ways: using “Absolute”/“World” coordinates, or a relative coordinate specification. Relative coordinates allow flexibility of rapid change to observe changes in building results due to orientation and position. “World” coordinates will facilitate use within a CADD system structure.

Relative coordinates make use of both Building and Zone North Axis values as well as Zone Origin values to locate the surface in 3D coordinate space. World coordinates do not use these values.

Typically, all zone origin values for “World” coordinates will be (0,0,0) but Building and Zone North Axis values may be used in certain instances (namely the Daylighting Coordinate Location entries).

Field: Daylighting Reference Point Coordinate System

Daylighting reference points need to be specified as well. Again, there can be two flavors; relative and world. Daylighting reference points must fit within the zone boundaries.

Relative coordinates make use of both Building and Zone North Axis values as well as Zone Origin values to locate the reference point in 3D coordinate space. World coordinates do not use these values.

Field: Rectangular Surface Coordinate System

Simple, rectangular surfaces (Wall:Exterior, Wall:Adiabatic, Wall:Underground, Wall:Interzone, Roof, Ceiling:Adiabatic, Ceiling:Interzone, Floor:GroundContact, Floor:Adiabatic, Floor:Interzone) can be specified with their Lower Left Corner as relative or world.

Relative (default) corners are specified relative to the Zone Origin for each surface. World corners would specify the absolute/world coordinate for this corner.

Surfaces

Surfaces make up the buildings and the elements that shade buildings. There are several methods to inputting surfaces, ranging from simple rectangular surfaces to detailed descriptions that describe each vertex in the order specified in the GlobalGeometryRules object. The simple, rectangular surface objects are described first with the more detailed descriptions following.

Walls

Walls are usually vertical (tilt = 90 degrees). These objects are used to describe exterior walls, interior walls (adiabatic), underground walls, and walls adjacent to other zones.

Wall:Exterior

The Wall:Exterior object is used to describe walls that are exposed to the external environment. They receive sun, wind – all the characteristics of the external world.

Field: Name

This is a unique name associated with the exterior wall. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

This is the name of the construction (ref: Construction) used in the surface. Regardless of location in the building, the “full” construction (all layers) is used. For example, for an interior wall separating two zones, zone x would have the outside layer (e.g. drywall) as the material that shows in zone y and then the layers to the inside layer – the material that shows in zone x. For symmetric constructions, the same construction can be used in the surfaces described in both zones.

Field: Zone Name

Field: Azimuth Angle

The Azimuth Angle indicates the direction that the wall faces (outward normal). The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Normally, walls are tilted 90 degrees and that is the default for this field.

Starting Corner for the surface

The rectangular surfaces specify the lower left corner of the surface for their starting coordinate. This is specified with (x,y,z) and can be relative to the zone origin or in world coordinates, depending on the value for rectangular surfaces specified in the GlobalGeometryRules object.

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Wall:Adiabatic

The Wall:Adiabatic object is used to describe interior walls and partitions. Adiabatic walls are used to describe walls next to zones that have the same thermal conditions (thus, no heat transfer).

Field: Name

This is a unique name associated with the interior wall. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Azimuth Angle

The Azimuth Angle indicates the direction that the wall faces (outward normal). The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Normally, walls are tilted 90 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Wall:Underground

The Wall:Underground object is used to describe walls with ground contact. The temperature at the outside of the wall is the temperature in the GroundTemperature:BuildingSurface object.

Field: Name

This is a unique name associated with the underground wall. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Azimuth Angle

The Azimuth Angle indicates the direction that the wall faces (outward normal). The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Normally, walls are tilted 90 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Wall:Interzone

The Wall:Interzone object is used to describe walls adjacent to zones that are significantly different conditions than the zone with this wall.

Field: Name

This is a unique name associated with the interzone wall. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Outside Boundary Condition Object

The Outside Boundary Condition Object field is the name of a wall in an adjacent zone or the name of the adjacent zone. If the adjacent zone option is used, the adjacent wall is automatically generated in the adjacent zone. If the surface name is used, it must be in the adjacent zone.

Field: Azimuth Angle

The Azimuth Angle indicates the direction that the wall faces (outward normal). The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Normally, walls are tilted 90 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Roofs/Ceilings

Roofs and ceilings are, by default, flat (tilt = 0 degrees). These objects are used to describe roofs, interior ceilings (adiabatic) and ceilings adjacent to other zones.

Roof

The Roof object is used to describe roofs that are exposed to the external environment.

Field: Name

This is a unique name associated with the roof. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Azimuth Angle

The Azimuth Angle indicates the direction of the outward normal for the roof. The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Flat roofs are tilted 0 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Width

Ceiling:Adiabatic

The Ceiling:Adiabatic object is used to describe interior ceilings that separate zones of like conditions.

Field: Name

This is a unique name associated with the ceiling. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Azimuth Angle

The Azimuth Angle indicates the direction of the outward normal for the roof. The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Flat ceilings are tilted 0 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Width

Ceiling:Interzone

The Ceiling:Interzone object is used to describe interior ceilings that separate zones of differing conditions (and expect heat transfer through the ceiling from the adjacent zone).

Field: Name

This is a unique name associated with the interzone ceiling. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Outside Boundary Condition Object

The Outside Boundary Condition Object field is the name of a floor in an adjacent zone or the name of the adjacent zone. If the adjacent zone option is used, the adjacent floor is automatically generated in the adjacent zone. If the surface name is used, it must be in the adjacent zone.

Field: Azimuth Angle

The Azimuth Angle indicates the direction of the outward normal for the roof. The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Flat ceilings are tilted 0 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Width

Floors

Floors are, by default, flat (tilt = 180 degrees). These objects are used to describe floors on the ground, interior floors (adiabatic) and floors adjacent to other zones.

Floor:GroundContact

The Floor:GroundContact object is used to describe floors that have ground contact (usually called slabs). The temperature at the outside of the floor is the temperature in the GroundTemperature:BuildingSurface object.

Field: Name

Field: Construction Name

Field: Zone Name

Field: Azimuth Angle

The Azimuth Angle indicates the direction of the outward normal for the roof. The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Flat floors are tilted 180 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Width

Floor:Adiabatic

The Floor:Adiabatict object is used to describe interior floors or floors that you wish to model with no heat transfer from the exterior to the floor.

Field: Name

Field: Construction Name

Field: Zone Name

Field: Azimuth Angle

The Azimuth Angle indicates the direction of the outward normal for the roof. The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Flat floors are tilted 180 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Width

Floor:Interzone

The Floor:Interzone object is used to describe floors that are adjacent to other zones that have differing conditions and you wish to model the heat transfer through the floor.

Field: Name

Field: Construction Name

Field: Zone Name

Field: Outside Boundary Condition Object

The Outside Boundary Condition Object field is the name of a ceiling in an adjacent zone or the name of the adjacent zone. If the adjacent zone option is used, the adjacent ceiling is automatically generated in the adjacent zone. If the surface name is used, it must be in the adjacent zone.

Field: Azimuth Angle

The Azimuth Angle indicates the direction of the outward normal for the roof. The angle is specified in degrees where East=90, South=180, West=270, North=0.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the wall is tilted from horizontal (or the ground). Flat floors are tilted 180 degrees and that is the default for this field.

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Width

Windows/Doors

The following window and door objects can be used to specify simple, rectangular doors and windows. In each case, the lower left corner (locator coordinate) of the window or door is specified relative to the surface it is on. Viewing the base surface as a planar surface, base the relative location from the lower left corner of the base surface. Vertex entry description as well as provisions for a few other surface types can be entered with the FenestrationSurface:Detailed object.

Window

The Window object is used to place windows on surfaces that can have windows, including exterior walls, interior walls, interzone walls, roofs, floors that are exposed to outdoor conditions, interzone ceiling/floors. These, of course, can be entered using the simple rectangular objects or the more detailed vertex entry objects.

Field: Name

Field: Construction Name

This is the name of the subsurface’s construction (ref: Construction and Construction:WindowDataFile).

For windows, if Construction Name is not found among the constructions on the input (.idf) file, the Window5 Data File (default Window5DataFile.dat) will be searched for that Construction Name (see “Importing Windows from WINDOW 5”). If that file is not present or if the Construction Name does not match the name of an entry on the file, an error will result. If there is a match, a window construction and its corresponding glass and gas materials will be created from the information read from the file.

Field: Building Surface Name

This is the name of a surface that contains this subsurface. Certain kinds of surfaces may not be allowed to have subsurfaces. For example, a surface in contact with the ground (e.g., Outside Boundary Condition = Ground) cannot contain a window. The window assumes the outward facing angle as well as the tilt angle of the base surface.

Field: Shading Control Name

This field, if not blank, is the name of the window shading control (ref: WindowProperty:ShadingControl) for this subsurface. It is used for Surface Type = Window and GlassDoor. To assign a shade to a window or glass door, see WindowMaterial: Shade. To assign a screen, see WindowMaterial:Screen. To assign a blind, see WindowMaterial:Blind. To assign switchable glazing, such as electrochromic glazing, see WindowProperty:ShadingControl.

Field: Frame and Divider Name

This field, if not blank, can be used to specify window frame, divider and reveal-surface data (ref: WindowProperty:FrameAndDivider). It is used only for exterior GlassDoors and rectangular exterior Windows, i.e., those with OutsideFaceEnvironment = Outdoors.

Field: Multiplier

This field is the number of identical items on the base surface. Using Multiplier can save input effort and calculation time. In the calculation the area (and area of frame and divider, if present and surface type is a window) is multiplied by Multiplier. The calculation of shadowing on the subsurfaces (and the calculation of the interior distribution of beam solar radiation transmitted by windows and glass doors) are done for the specified subsurface position and dimensions.

Multiplier should be used with caution. Multiplier > 1 can give inaccurate or nonsensical results in situations where the results are sensitive to window or glass door position. This includes shadowing on the window/glass door, daylighting from the window/glass door, and interior distribution of solar radiation from the window/glass door. In these cases, the results for the single input window/glass door, after multiplication, may not be representative of the results you would get if you entered each of the multiple subsurfaces separately.

--a warning if Solar Distribution = FullExterior or FullInteriorAndExterior (ref: Building - Field: Solar Distribution), indicating that the shadowing on the input window or the interior solar radiation distribution from the input window may not be representative of the actual group of windows. No warning is issued if Solar Distribution = MinimalShadowing.

--an error if the window is an exterior window/glass door in a zone that has a detailed daylighting calculation (Daylighting:Detailed specified for the zone). Since a single window with a multiplier can never give the same daylight illuminance as the actual set of windows, you are not allowed to use Multiplier in this situation.

Starting Corner for the surface

The rectangular subsurfaces specify the lower left corner of the surface for their starting coordinate. This corner is specifed relative to the lower left corner of the base surface by specifying the X and Z values from that corner.

Field: Starting X Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Door

The Door object is used to place opaque doors on surfaces that can have doors, including exterior walls, interior walls, interzone walls, roofs, floors that are exposed to outdoor conditions, interzone ceiling/floors. These, of course, can be entered using the simple rectangular objects or the more detailed vertex entry objects.

Field: Name

Field: Construction Name

Field: Building Surface Name

This is the name of a surface that contains this subsurface. Certain kinds of surfaces may not be allowed to have subsurfaces. The door assumes the outward facing angle as well as the tilt angle of the base surface.

Field: Multiplier

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

GlazedDoor

The GlazedDoor object is used to place doors on surfaces that can have doors, including exterior walls, interior walls, interzone walls, roofs, floors that are exposed to outdoor conditions, interzone ceiling/floors. These, of course, can be entered using the simple rectangular objects or the more detailed vertex entry objects.

Field: Name

Field: Construction Name

This is the name of the subsurface’s construction (ref: Construction and Construction:WindowDataFile).

Field: Building Surface Name

This is the name of a surface that contains this subsurface. Certain kinds of surfaces may not be allowed to have subsurfaces. For example, a surface in contact with the ground (Outside Boundary Condition = Ground) cannot contain a window. The door assumes the outward facing angle as well as the tilt angle of the base surface.

Field: Shading Control Name

Field: Frame and Divider Name

Field: Multiplier

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Window:Interzone

The Window:Interzone object is used to place windows on surfaces that can have windows, including interzone walls, interzone ceiling/floors. These, of course, can be entered using the simple rectangular objects or the more detailed vertex entry objects.

Field: Name

Field: Construction Name

This is the name of the subsurface’s construction (ref: Construction and Construction:WindowDataFile).

Field: Building Surface Name

This is the name of a surface that contains this subsurface. Certain kinds of surfaces may not be allowed to have subsurfaces. For example, a surface in contact with the ground (Outside Boundary Condition = Ground) cannot contain a window. The window assumes the outward facing angle as well as the tilt angle of the base surface.

Field: Outside Boundary Condition Object

The Outside Boundary Condition Object field is the name of a window in an adjacent zone or the name of the adjacent zone. If the adjacent zone option is used, the adjacent ceiling is automatically generated in the adjacent zone. If the surface name is used, it must be in the adjacent zone.

Field: Multiplier

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Door:Interzone

The Door:Interzone object is used to place opaque doors on surfaces that can have doors, including interzone walls, interzone ceiling/floors. These, of course, can be entered using the simple rectangular objects or the more detailed vertex entry objects.

Field: Name

Field: Construction Name

Field: Building Surface Name

Field: Outside Boundary Condition Object

The Outside Boundary Condition Object field is the name of a door in an adjacent zone or the name of the adjacent zone. If the adjacent zone option is used, the adjacent ceiling is automatically generated in the adjacent zone. If the surface name is used, it must be in the adjacent zone.

Field: Multiplier

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

GlazedDoor:Interzone

The GlazedDoor:Interzone object is used to place doors on surfaces that can have doors, including interzone walls, interzone ceiling/floors. These, of course, can be entered using the simple rectangular objects or the more detailed vertex entry objects.

Field: Name

Field: Construction Name

This is the name of the subsurface’s construction (ref: Construction and Construction:WindowDataFile).

Field: Building Surface Name

Field: Outside Boundary Condition Object

The Outside Boundary Condition Object field is the name of a glazed (glass) door in an adjacent zone or the name of the adjacent zone. If the adjacent zone option is used, the adjacent ceiling is automatically generated in the adjacent zone. If the surface name is used, it must be in the adjacent zone.

Field: Multiplier

Starting Corner for the surface

Field: Starting X Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Examples of the rectangular surfaces are found in the example files 4ZoneWithShading_Simple_1.idf and 4ZoneWithShading_Simple_2. Some examples:

Wall:Exterior,

Zn001:Wall001, !- Name

EXTERIOR, !- Construction Name

ZONE 1, !- Zone Name

180, !- Azimuth Angle {deg}

90, !- Tilt Angle {deg}

0, !- Starting X Coordinate {m}

0, !- Starting Y Coordinate {m}

0, !- Starting Z Coordinate {m}

20, !- Length {m}

10; !- Height {m}

Window,

Zn001:Wall001:Win001, !- Name

SINGLE PANE HW WINDOW, !- Construction Name

Zn001:Wall001, !- Building Surface Name

, !- Shading Control Name

, !- Frame and Divider Name

1, !- Multiplier

4, !- Starting X Coordinate {m}

3, !- Starting Z Coordinate {m}

3, !- Length {m}

5; !- Height {m}

Door,

Zn001:Wall001:Door001, !- Name

HOLLOW WOOD DOOR, !- Construction Name

Zn001:Wall001, !- Building Surface Name

1, !- Multiplier

14, !- Starting X Coordinate {m}

0, !- Starting Z Coordinate {m}

3, !- Length {m}

5; !- Height {m}

Wall:Adiabatic,

Zn001:Wall004, !- Name

INTERIOR, !- Construction Name

ZONE 1, !- Zone Name

90, !- Azimuth Angle {deg}

90, !- Tilt Angle {deg}

20, !- Starting X Coordinate {m}

0, !- Starting Y Coordinate {m}

0, !- Starting Z Coordinate {m}

20, !- Length {m}

10; !- Height {m}

Floor:Adiabatic,

Zn001:Flr001, !- Name

FLOOR, !- Construction Name

ZONE 1, !- Zone Name

90, !- Azimuth Angle {deg}

180, !- Tilt Angle {deg}

0, !- Starting X Coordinate {m}

0, !- Starting Y Coordinate {m}

0, !- Starting Z Coordinate {m}

20, !- Length {m}

20; !- Width {m}

Ceiling:Interzone,

Zn001:Roof001, !- Name

CEILING34, !- Construction Name

ZONE 1, !- Zone Name

Zn003:Flr001, !- Outside Boundary Condition Object

180, !- Azimuth Angle {deg}

0, !- Tilt Angle {deg}

0, !- Starting X Coordinate {m}

0, !- Starting Y Coordinate {m}

10, !- Starting Z Coordinate {m}

20, !- Length {m}

20; !- Width {m}

Window,

Zn002:Wall001:Win001, !- Name

SINGLE PANE HW WINDOW, !- Construction Name

Zn002:Wall001, !- Building Surface Name

, !- Shading Control Name

, !- Frame and Divider Name

1, !- Multiplier

4, !- Starting X Coordinate {m}

3, !- Starting Z Coordinate {m}

3, !- Length {m}

5; !- Height {m}

Surface Vertices

use the same vertex input. The numeric parameters indicated below are taken from the BuildingSurface:Detailed definition; the others may not be exactly the same but are identical in configuration. They are also “extensible” – so, if you want more vertices for these surfaces, you may add to the IDD definition as indicated in the “extensible” comment or, as EnergyPlus is “auto-extensible” just add the number of vertices into your input file.. Note that FenestrationSurface:Detailed is not extensible and is limited to 4 (max) vertices. If you leave the Number of Surface Vertex groups blank or enter autocalculate, EnergyPlus looks at the number of groups entered and figures out how many coordinate groups are entered.

The figure above will help illustrate Surface Vertex entry. The convention used in “GlobalGeometryRules” dictates the order of the vertices (ref: GlobalGeometryRules). In this example, the conventions used are Starting Vertex Position = UpperLeftCorner and Vertex Entry Direction= CounterClockwise. The surfaces for this single zone are:

Note that in this example, point 1 of the entry is the Upper Left Corner of the rectangular surfaces and the point of the triangle for the 3 sided surface. The east wall shows the order of vertex entry. For horizontal surfaces, any vertex may be chosen as the starting position, but the Vertex Entry Direction convention must be followed. The surface details report (Output: Surfaces:List, Details;) is very useful for reviewing the accuracy of surface geometry inputs (ref: Surface Output Variables/Reports and Variable Dictionary Reports).

From the detailed vertices, EnergyPlus tries to determine the “height” and “width” of the surface. Obviously, this doesn’t work well for >4 sided surfaces; for these, if the calculated height and width are not close to the gross area for the surface, the height and width shown will be the square root of the area (and thus a square).

Building Surfaces - Detailed

A building surface is necessary for all calculations. There must be at least one building surface per zone. You can use the detailed descriptions as shown below or the simpler, rectangular surface descriptions shown earlier.

Wall:Detailed

Field: Name

This is a unique name associated with each building surface. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Outside Boundary Condition

This value can be one of several things depending on the actual kind of surface.

1) Surface – if this surface is an internal surface, then this is the choice. The value will either be a surface in the base zone or a surface in another zone. The heat balance between two zones can be accurately simulated by specifying a surface in an adjacent zone. EnergyPlus will simulate a group of zones simultaneously and will include the heat transfer between zones. However, as this increases the complexity of the calculations, it is not necessary to specify the other zone unless the two zones will have a significant temperature difference. If the two zones will not be very different (temperature wise), then the surface should use itself as the outside environment or specify this field as Adiabatic. The surface name on the “outside” of this surface (adjacent to) is placed in the next field.

2) Adiabatic – an internal surface in the same Zone. This surface will not transfer heat out of the zone, but will still store heat in thermal mass. Only the inside face of the surface will exchange heat with the zone (i.e. two adiabatic surfaces are required to model internal partitions where both sides of the surface are exchanging heat with the zone). The Outside Boundary Condition Object can be left blank.

3) Zone – this is similar to Surface but EnergyPlus will automatically create the required surface in the adjacent zone when this is entered for the surface. If there are windows or doors on the surface, EnergyPlus automatically creates appropriate sub-surfaces as well.

4) Outdoors – if this surface is exposed to outside temperature conditions, then this is the choice. See Sun Exposure and Wind Exposure below for further specifications on this kind of surface.

5) Ground – if this surface is exposed to the ground, then this is the usual choice. The temperature on the outside of this surface will be the Site:GroundTemperature:Surface value for the month. For more information on ground contact surfaces, reference the Auxiliary Programs document section on “Ground Heat Transfer in EnergyPlus”.

6) GroundFCfactorMethod – if this surface is exposed to the ground and using the Construction:CfactorUndergroundWall, then this is the choice. The temperature on the outside of this surface will be the Site:GroundTemperature:FcfactorMethod value for the month.

7) OtherSideCoefficients – if this surface has a custom, user specified temperature or other parameters (See SurfaceProperty:OtherSideCoefficients specification), then this is the choice. The outside boundary condition will be the name of the SurfaceProperty:OtherSideCoefficients specification.

8) OtherSideConditionsModel – if this surface has a specially-modeled multi-skin component, such as a transpired collector or vented photovoltaic panel, attached to the outside (See SurfaceProperty:OtherSideConditionsModel specification), then this the choice. The outside face environment will be the name of the SurfaceProperty:OtherSideConditionsModelspecification.

9) GroundSlabPreprocessorAverage – uses the average results from the Slab preprocessor calculations.

10) GroundSlabPreprocessorCore – uses the core results from the Slab preprocessor calculations.

11) GroundSlabPreprocessorPerimeter – uses the perimeter results from the Slab preprocessor calculations.

12) GroundBasementPreprocessorAverageWall – uses the average wall results from the Basement preprocessor calculations.

13) GroundBasementPreprocessorAverageFloor – uses the average floor results from the Basement preprocessor calculations.

14) GroundBasementPreprocessorUpperWall – uses the upper wall results from the Basement preprocessor calculations.

15) GroundBasementPreprocessorLowerWall – uses the lower wall results from the Basement preprocessor calculations.

Field: Outside Boundary Condition Object

If neither Surface, OtherSideCoefficients, or OtherSideConditionsModel are specified for the Outside Boundary Condition (previous field), then this field should be left blank.

As stated above, if the Outside Boundary Condition is “Surface”, then this field’s value must be the surface name whose inside face temperature will be forced on the outside face of the base surface. This permits heat exchange between adjacent zones (interzone heat transfer) when multiple zones are simulated, but can also be used to simulate middle zone behavior without modeling the adjacent zones. This is done by specifying a surface within the zone. For example, a middle floor zone can be modeled by making the floor the Outside Boundary Condition Object for the ceiling, and the ceiling the Outside Boundary Condition Object for the floor.

If the Outside Boundary Condition is Zone, then this field should contain the zone name of the adjacent zone for the surface.

Equally, if the Outside Boundary Condition is “OtherSideCoefficients”, then this field’s value must be the SurfaceProperty:OtherSideCoefficients name. Or if the Outside Boundary Condition is “OtherSideConditionsModel” then this field’s value must be the SurfaceProperty:OtherSideConditionsModel name.

Field: Sun Exposure

If the surface is exposed to the sun, then “SunExposed” should be entered in this field. Otherwise, “NoSun” should be entered.

Field: Wind Exposure

If the surface is exposed to the Wind, then “WindExposed” should be entered in this field. Otherwise, “NoWind” should be entered.

Note: When a surface is specified with “NoWind”, this has several implications. Within the heat balance code, this surface will default to using the simple ASHRAE exterior convection coefficient correlation with a zero wind speed. In addition, since the ASHRAE simple method does not have a separate value for equivalent long wavelength radiation to the sky and ground, using “NoWind” also eliminates long wavelength radiant exchange from the exterior of the surface to both the sky and the ground. Thus, only simple convection takes place at the exterior face of a surface specified with “NoWind”.

Field: View Factor to Ground

The fraction of the ground plane (assumed horizontal) that is visible from a heat-transfer surface. It is used to calculate the diffuse solar radiation from the ground that is incident on the surface.

For example, if there are no obstructions, a vertical surface sees half of the ground plane and so View Factor to Ground = 0.5. A horizontal downward-facing surface sees the entire ground plane, so View Factor to Ground = 1.0. A horizontal upward-facing surface (horizontal roof) does not see the ground at all, so View Factor to Ground = 0.0.

Unused if reflections option in Solar Distribution field in Building object input unless a DaylightingDevice:Shelf or DaylightingDevice:Tubular has been specified.

If you do not use the reflections option in the Solar Distribution field in your Building object input, you are responsible for entering the View Factor to Ground for each heat-transfer surface. Typical values for a surface that is not shadowed are obtained by the simple equation:

For example, this gives 0.5 for a wall of tilt 90°. If the tilt of the wall changes, then the View Factor to Ground must also change.

If you enter autocalculate in this field, EnergyPlus will automatically calculate the view factor to ground based on the tilt of the surface.

If you do use the reflections option in the Solar Distribution field in your Building object input, you do not have to enter View Factor to Ground values. In this case the program will automatically calculate the value to use for each exterior surface taking into account solar shadowing (including shadowing of the ground by the building) and reflections from obstructions (ref: Building, Field: Solar Distribution).

However, if you do use the reflections option AND you are modeling a DaylightingDevice:Shelf or DaylightingDevice:Tubular, then you still need to enter some values of View Factor to Ground. For DaylightingDevice:Shelf you need to enter View Factor to Ground for the window associated with the shelf. And for DaylightingDevice:Tubular you need to enter the View Factor to Ground for the FenestrationSurface:Detailed corresponding to the dome of the tubular device.

Note 1: The corresponding view factor to the sky for diffuse solar radiation is not a user input; it is calculated within EnergyPlus based on surface orientation, sky solar radiance distribution, and shadowing surfaces.

Note 2: The view factors to the sky and ground for thermal infrared (long-wave) radiation are not user inputs; they are calculated within EnergyPlus based on surface tilt and shadowing surfaces. Shadowing surfaces are considered to have the same emissivity and temperature as the ground, so they are lumped together with the ground in calculating the ground IR view factor.

Field: Number of Vertices

This field specifies the number of sides in the surface (number of X,Y,Z vertex groups). For further information, see the discussion on “Surface Vertices” above.

RoofCeiling:Detailed

Field: Name

This is a unique name associated with each building surface. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Outside Boundary Condition

This value can be one of several things depending on the actual kind of surface.

4) Outdoors – if this surface is exposed to outside temperature conditions, then this is the choice. See Sun Exposure and Wind Exposure below for further specifications on this kind of surface.

5) Ground – if this surface is exposed to the ground, then this is the choice. The temperature on the outside of this surface will be the Ground Temperature.

6) OtherSideCoefficients – if this surface has a custom, user specified temperature or other parameters (See SurfaceProperty:OtherSideCoefficients specification), then this is the choice. The outside boundary condition will be the name of the SurfaceProperty:OtherSideCoefficients specification.

7) OtherSideConditionsModel – if this surface has a specially-modeled multi-skin component, such as a transpired collector or vented photovoltaic panel, attached to the outside (See SurfaceProperty:OtherSideConditionsModel specification), then this the choice. The outside face environment will be the name of the SurfaceProperty:OtherSideConditionsModelspecification.

8) GroundSlabPreprocessorAverage – uses the average results from the Slab preprocessor calculations.

9) GroundSlabPreprocessorCore – uses the core results from the Slab preprocessor calculations.

10) GroundSlabPreprocessorPerimeter – uses the perimeter results from the Slab preprocessor calculations.

11) GroundBasementPreprocessorAverageWall – uses the average wall results from the Basement preprocessor calculations.

12) GroundBasementPreprocessorAverageFloor – uses the average floor results from the Basement preprocessor calculations.

13) GroundBasementPreprocessorUpperWall – uses the upper wall results from the Basement preprocessor calculations.

14) GroundBasementPreprocessorLowerWall – uses the lower wall results from the Basement preprocessor calculations.

Field: Outside Boundary Condition Object

If neither Surface, OtherSideCoefficients, or OtherSideConditionsModel are specified for the Outside Boundary Condition (previous field), then this field should be left blank.

If the Outside Boundary Condition is Zone, then this field should contain the zone name of the adjacent zone for the surface.

Field: Sun Exposure

If the surface is exposed to the sun, then “SunExposed” should be entered in this field. Otherwise, “NoSun” should be entered.

Field: Wind Exposure

If the surface is exposed to the Wind, then “WindExposed” should be entered in this field. Otherwise, “NoWind” should be entered.

Field: View Factor to Ground

Unused if reflections option in Solar Distribution field in Building object input unless a DaylightingDevice:Shelf or DaylightingDevice:Tubular has been specified.

For example, this gives 0.5 for a wall of tilt 90°. If the tilt of the wall changes, then the View Factor to Ground must also change.

If you enter autocalculate in this field, EnergyPlus will automatically calculate the view factor to ground based on the tilt of the surface.

Field: Number of Vertices

This field specifies the number of sides in the surface (number of X,Y,Z vertex groups). For further information, see the discussion on “Surface Vertices” above.

Floor:Detailed

Field: Name

This is a unique name associated with each building surface. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Construction Name

Field: Zone Name

Field: Outside Boundary Condition

This value can be one of several things depending on the actual kind of surface.

4) Outdoors – if this surface is exposed to outside temperature conditions, then this is the choice. See Sun Exposure and Wind Exposure below for further specifications on this kind of surface.

6) GroundFCfactorMethod – if this surface is exposed to the ground and using the Construction:FfactorGroundFloor, then this is the choice. The temperature on the outside of this surface will be the Site:GroundTemperature:FcfactorMethod value for the month.

9) GroundSlabPreprocessorAverage – uses the average results from the Slab preprocessor calculations.

10) GroundSlabPreprocessorCore – uses the core results from the Slab preprocessor calculations.

11) GroundSlabPreprocessorPerimeter – uses the perimeter results from the Slab preprocessor calculations.

12) GroundBasementPreprocessorAverageWall – uses the average wall results from the Basement preprocessor calculations.

13) GroundBasementPreprocessorAverageFloor – uses the average floor results from the Basement preprocessor calculations.

14) GroundBasementPreprocessorUpperWall – uses the upper wall results from the Basement preprocessor calculations.

15) GroundBasementPreprocessorLowerWall – uses the lower wall results from the Basement preprocessor calculations.

Field: Outside Boundary Condition Object

If neither Surface, OtherSideCoefficients, or OtherSideConditionsModel are specified for the Outside Boundary Condition (previous field), then this field should be left blank.

If the Outside Boundary Condition is Zone, then this field should contain the zone name of the adjacent zone for the surface.

Field: Sun Exposure

If the surface is exposed to the sun, then “SunExposed” should be entered in this field. Otherwise, “NoSun” should be entered.

Field: Wind Exposure

If the surface is exposed to the Wind, then “WindExposed” should be entered in this field. Otherwise, “NoWind” should be entered.

Field: View Factor to Ground

Unused if reflections option in Solar Distribution field in Building object input unless a DaylightingDevice:Shelf or DaylightingDevice:Tubular has been specified.

For example, this gives 0.5 for a wall of tilt 90°. If the tilt of the wall changes, then the View Factor to Ground must also change.

If you enter autocalculate in this field, EnergyPlus will automatically calculate the view factor to ground based on the tilt of the surface.

Field: Number of Vertices

This field specifies the number of sides in the surface (number of X,Y,Z vertex groups). For further information, see the discussion on “Surface Vertices” above.

BuildingSurface:Detailed

The BuildingSurface:Detailed object can more generally describe each of the surfaces.

Field: Name

This is a unique name associated with each building surface. It is used in several other places as a reference (e.g. as the base surface name for a Window or Door).

Field: Surface Type

Used primarily for convenience, the surface type can be one of the choices illustrated above – Wall, Floor, Ceiling, Roof. Azimuth (facing) and Tilt are determined from the vertex coordinates. Note that “normal” floors will be tilted 180° whereas flat roofs/ceilings will be tilted 0°. EnergyPlus uses this field’s designation, along with the calculated tilt of the surface, to issue warning messages when tilts are “out of range”. Calculations in EnergyPlus use the actual calculated tilt values for the actual heat balance calculations. Note, however, that a floor tilted 0° is really facing “into” the zone and is not what you will desire for the calculations even though the coordinate may appear correct in the viewed DXF display.

“Normal” tilt for walls is 90° -- here you may use the calculated Azimuth to make sure your walls are facing away from the zone’s interior.

Field: Construction Name

Field: Zone Name

Field: Outside Boundary Condition

This value can be one of several things depending on the actual kind of surface.

1) Surface – if this surface is an internal surface, then this is the choice. The value will either be a surface in the base zone or a surface in another zone. The heat balance between two zones can be accurately simulated by specifying a surface in an adjacent zone. EnergyPlus will simulate a group of zones simultaneously and will include the heat transfer between zones. However, as this increases the complexity of the calculations, it is not necessary to specify the other zone unless the two zones will have a significant temperature difference. If the two zones will not be very different (temperature wise), then the surface should use itself as the outside environment or specify this field as Adiabatic. In either case, the surface name on the “outside” of this surface (adjacent to) is placed in the next field.

4) Outdoors – if this surface is exposed to outside temperature conditions, then this is the choice. See Sun Exposure and Wind Exposure below for further specifications on this kind of surface.

6) GroundFCfactorMethod – if this surface is exposed to the ground and using the Construction:CfactorUndergroundWall or Construction:FfactorGroundFloor (depending on surface type), then this is the choice. The temperature on the outside of this surface will be the Site:GroundTemperature:FcfactorMethod value for the month.

9) GroundSlabPreprocessorAverage – uses the average results from the Slab preprocessor calculations.

10) GroundSlabPreprocessorCore – uses the core results from the Slab preprocessor calculations.

11) GroundSlabPreprocessorPerimeter – uses the perimeter results from the Slab preprocessor calculations.

12) GroundBasementPreprocessorAverageWall – uses the average wall results from the Basement preprocessor calculations.

13) GroundBasementPreprocessorAverageFloor – uses the average floor results from the Basement preprocessor calculations.

14) GroundBasementPreprocessorUpperWall – uses the upper wall results from the Basement preprocessor calculations.

15) GroundBasementPreprocessorLowerWall – uses the lower wall results from the Basement preprocessor calculations.

Field: Outside Boundary Condition Object

If neither Surface, OtherSideCoefficients, or OtherSideConditionsModel are specified for the Outside Boundary Condition (previous field), then this field should be left blank.

If the Outside Boundary Condition is Zone, then this field should contain the zone name of the adjacent zone for the surface.

Field: Sun Exposure

If the surface is exposed to the sun, then “SunExposed” should be entered in this field. Otherwise, “NoSun” should be entered.

Field: Wind Exposure

If the surface is exposed to the Wind, then “WindExposed” should be entered in this field. Otherwise, “NoWind” should be entered.

Field: View Factor to Ground

Unused if reflections option in Solar Distribution field in Building object input unless a DaylightingDevice:Shelf or DaylightingDevice:Tubular has been specified.

For example, this gives 0.5 for a wall of tilt 90°. If the tilt of the wall changes, then the View Factor to Ground must also change.

If you enter autocalculate in this field, EnergyPlus will automatically calculate the view factor to ground based on the tilt of the surface.

Field: Number of Vertices

This field specifies the number of sides in the surface (number of X,Y,Z vertex groups). For further information, see the discussion on “Surface Vertices” above.

IDF example of three walls (first is an exterior wall, second and third are interzone partitions):

FenestrationSurface:Detailed

This surface class is used for subsurfaces, which can be of five different types: Windows, Doors, GlassDoors, TubularDaylightDomes, and TubularDaylightDiffusers. A subsurface (such as a window) of a base surface (such as a wall) inherits several of the properties (such as Outside Boundary Condition, Sun Exposure, etc.) of the base surface. Windows, GlassDoors, TubularDaylightDomes, and TubularDaylightDiffusers are considered to have one or more glass layers and so transmit solar radiation. Doors are considered to be opaque.

Field: Name

This is a unique name associated with the heat transfer subsurface. It may be used in other places as a reference (e.g. as the opposing subsurface of an interzone window or door).

Field: Surface Type

The choices for Surface Type are Window, Door, GlassDoor, TubularDaylightDome, and TubularDaylightDiffuser. Doors are assumed to be opaque (do not transmit solar radiation) whereas the other surface types do transmit solar radiation. Windows and Glass Doors are treated identically in the calculation of conduction heat transfer, solar gain, daylighting, etc. A Window or GlassDoor, but not a Door, can have a movable interior, exterior or between-glass shading device, such as blinds (ref: WindowMaterial:Blind), and can have a frame and/or a divider (ref: WindowProperty:FrameAndDivider). TubularDaylightDomes and TubularDaylightDomes are specialized subsurfaces for use with the DaylightingDevice:Tubular object to simulate Tubular Daylighting Devices (TDDs). TubularDaylightDomes and TubularDaylightDomes cannot have shades, screens or blinds. In the following, the term “window” applies to Window, GlassDoor, TubularDaylightDome, and TubularDaylightDome, if not otherwise explicitly mentioned.

As noted in the description of the BuildingSurface:Detailed, Azimuth (facing angle) and Tilt are calculated from the entered vertices. Tilts of subsurfaces will normally be the same as their base surface. If these are significantly beyond the “normals” for the base surface, warning messages may be issued. If the facing angles are not correct, you may have a window pointing “into” the zone rather than out of it – this would cause problems in the calculations. Note, too, that a “reveal” (inset or outset) may occur if the plane of the subsurface is not coincident with the base surface; the reveal has an effect on shading of the subsurface.

Field: Construction Name

This is the name of the subsurface’s construction (ref: Construction [for Window, GlassDoor and Door] and Construction:WindowDataFile [for Window and GlassDoor]).

For windows, if Construction Name is not found among the constructions on the input (.idf) file, the Window5 Data File (Window5DataFile.dat) will be searched for that Construction Name (see “Importing Windows from WINDOW 5”). If that file is not present or if the Construction Name does not match the name of an entry on the file, an error will result. If there is a match, a window construction and its corresponding glass and gas materials will be created from the information read from the file.

Field: Building Surface Name

Field: Outside Boundary Condition Object

If the base surface has Outside Boundary Condition = Surface or OtherSideCoefficients, then this field must also be specified for the subsurface. Otherwise, it can be left blank.

If the base surface has Outside Boundary Condition = Zone, then this surface retains that characteristic and uses the same zone of the base surface. It can be entered here for clarity or it can be left blank.

If Outside Boundary Condition for the base surface is Surface, this field should specify the subsurface in the opposing zone that is the counterpart to this subsurface. The constructions of the subsurface and opposing subsurface must match, except that, for multi-layer constructions, the layer order of the opposing subsurface’s construction must be the reverse of that of the subsurface.

If Outside Boundary Condition for the base surface is OtherSideCoefficients, this field could specify the set of SurfaceProperty:OtherSideCoefficients for this subsurface. If this is left blank, then the Other Side Coefficients of the base surface will be used for this subsurface. Windows and GlassDoors are not allowed to have Other Side Coefficients.

Field: View Factor to Ground

Unused if reflections option in Solar Distribution field in Building object input unless a Daylighting Device:Shelf or Daylighting Device:Tubular has been specified.

For example, this gives 0.5 for a wall of tilt 90°. If the tilt of the wall changes, then the View Factor to Ground must also change.

If you enter autocalculate in this field, EnergyPlus will automatically calculate the view factor to ground based on the tilt of the surface.

If you do use the reflections option in the Solar Distribution field in your BUILDING object input, you do not have to enter View Factor to Ground values. In this case the program will automatically calculate the value to use for each exterior surface taking into account solar shadowing (including shadowing of the ground by the building) and reflections from obstructions (ref: Building, Field: Solar Distribution).

Field: Shading Control Name

Field: Frame and Divider Name

Field: Multiplier

Used only for Surface Type = Window, Door or Glass Door. It is the number of identical items on the base surface. Using Multiplier can save input effort and calculation time. In the calculation the area (and area of frame and divider, if present and surface type is a window) is multiplied by Multiplier. The calculation of shadowing on the subsurfaces (and the calculation of the interior distribution of beam solar radiation transmitted by windows and glass doors) are done for the specified subsurface position and dimensions.

Field: Number of Vertices

The number of sides the surface has (number of X,Y,Z vertex groups). For further information, see the discussion on “Surface Vertices” above. Door and GlassDoor subsurfaces are rectangular and therefore have four vertices. Window subsurfaces can be rectangular or triangular and therefore have four or three vertices, respectively.

Fields: Vertex Coordinates

This is a total of twelve fields giving the x,y,z coordinate values of the four vertices of rectangular subsurfaces [m], or a total of nine fields giving the x,y,z coordinate values of the three vertices of triangular windows.

For triangular windows the first vertex listed can be any of the three vertices, but the order of the vertices should be counter-clockwise if VertexEntry is CounterClockWise and clockwise if VertexEntry is ClockWise (ref: GlobalGeometryRules).

Window Modeling Options

The following table shows what input objects/fields to use to model different window options. It also gives the name of an example input, if available, that demonstrates the option.

InternalMass

Any surface that would logically be described as an interior wall, floor or ceiling can just as easily be described as Internal Mass. Internal Mass surface types only exchange energy with the zone in which they are described; they do not see any other zones. There are two approaches to using internal mass. The first approach is to have several pieces of internal mass with each piece having a different construction type. The other approach is to choose an average construction type and combine all of the interior surfaces into a single internal mass. Similar to internal surfaces with an adiabatic boundary condtion, the zone will only exchange energy with the inside of the Internal Mass construction. If both sides of the surface exchange energy with the zone then the user should input twice the area when defining the Internal Mass object. Note that furniture and other large objects within a zone can be described using internal mass. However, simplifying calculations using internal mass must be used with caution when the “FullInteriorAndExterior” or “FullInteriorAndExteriorWithReflections” Solar Distribution model (see Building parameters) is chosen.

Example

When zoning an office building, five west-facing offices have been combined into one zone. All of the offices have interior walls made of the same materials. As shown in the figure below, this zone may be described with 5 exterior walls and 11 internal walls or 1 exterior wall and 1 internal mass. Note that fewer surfaces will speed up the EnergyPlus calculations.

Example

A five-story building has the same ceiling/floor construction separating each of the levels. Zones that are on floors 2 through 4 may be described using a single piece of internal mass to represent both the floor and ceiling. The construction for this internal mass would be identical to the ceiling/floor construction that would be used to describe separate surfaces and the area of the internal mass surface would be the total surface area of the combined ceilings/floors (i.e. twice the total floor area).

Field: Name

This is a unique character string associated with the internal mass surface. Though it must be unique from other surface names, it is used primarily for convenience with internal mass surfaces.

Field: Construction Name

Field: Zone Name

Field: Surface Area

This field is the surface area of the internal mass. The area that is specified must be the entire surface area that is exposed to the zone. If both sides of a wall are completely within the same zone, then the area of both sides must be included when describing that internal wall.

Surface Output Variables/Reports

Note that Surface Outputs from specialized algorithms (such as Effective Moisture Penetration Depth (EMPD), Combined Heat and Moisture Transport (HAMT) and Conduction Finite Difference are discussed under the objects that describe the specialized inputs for these algorithms). You can access them via these links:

Output variables applicable to opaque heat transfer surfaces (FLOOR, WALL, ROOF, DOOR). Note – these are advanced variables – you must read the descriptions and understand before use – then you must use the Diagnostics object to allow reporting.

Window Output Variables

Zone,Average,Zone Transmitted Solar[W]

Zone,Sum,Zone Transmitted Solar Energy[J]

Zone,Average,Zone Window Heat Gain[W]

Zone,Sum,Zone Window Heat Gain Energy[J]

Zone,Average,Zone Window Heat Loss[W]

Zone,Sum,Zone Window Heat Loss Energy[J]

Zone,Average,Zone Beam Solar from Exterior Windows[W]

Zone,Sum,Zone Beam Solar from Exterior Windows Energy[J]

Zone,Average,Zone Diff Solar from Exterior Windows[W]

Zone,Sum,Zone Diff Solar from Exterior Windows Energy[J]

Zone,Average,Window Solar Absorbed:All Glass Layers[W]

Zone,Average,Total Shortwave Absorbed:All Glass Layers[W]

Zone,Sum,Window Solar Absorbed:All Glass Layers Energy[J]

Zone,Average,Window Solar Absorbed:Shading Device[W]

Zone,Average,Window Transmitted Solar[W]

Zone,Sum,Window Transmitted Solar Energy[J]

Zone,Average,Window Transmitted Beam Solar[W]

Zone,Average,Window Transmitted Beam-to-Beam Solar[W]

Zone,Average,Window Transmitted Beam-to-Diffuse Solar[W]

Zone,Sum,Window Transmitted Beam Solar Energy[J]

Zone,Sum,Window Transmitted Beam-to-Beam Solar Energy[J]

Zone,Sum,Window Transmitted Beam-to-Diffuse Solar Energy[J]

Zone,Average,Window Transmitted Diffuse Solar[W]

Zone,Sum,Window Transmitted Diffuse Solar Energy[J]

Zone,Average,Window System Solar Transmittance[]

Zone,Average,Window System Solar Absorptance[]

Zone,Average,Window System Solar Reflectance[]

Zone,Average,Window Gap Convective Heat Flow[W]

Zone,Sum,Window Gap Convective Heat Flow Energy[J]

Zone,Average,Window Heat Gain[W]

Zone,Sum,Window Heat Gain Energy[J]

Zone,Average,Window Heat Loss[W]

Zone,Sum,Window Heat Loss Energy[J]

Zone,Average,Glass Beam-Beam Solar Transmittance[]

Zone,Average,Glass Diffuse-Diffuse Solar Transmittance[]

Zone,Average,Window Calculation Iterations[]

Zone,Average,Solar Horizontal Profile Angle[degree]

Zone,Average,Solar Vertical Profile Angle[degree]

Zone,Average,Beam Solar Reflected by Outside Reveal Surfaces[W]

Zone,Average,Beam Solar Reflected by Inside Reveal Surfaces[W]

Zone,Average,Inside Glass Condensation Flag[]

Zone,Average,Inside Frame Condensation Flag[]

Zone,Average,Inside Divider Condensation Flag[]

Zone,Average,Fraction of Time Shading Device Is On[]

Zone,Average,Window Blind Slat Angle [deg]

Zone,Average,Blind Beam-Beam Solar Transmittance[]

Zone,Average,Blind Beam-Diffuse Solar Transmittance[]

Zone,Average,Blind Diffuse-Diffuse Solar Transmittance[]

Zone,Average,Blind/Glass System Beam-Beam Solar Transmittance[]

Zone,Average,Blind/Glass System Diffuse-Diffuse Solar Transmittance[]

Zone,State,Storm Window On/Off Flag[]

Zone,Average,Window Heat Gain from Frame and Divider to Zone [W]

Zone,Average,Window Frame Heat Gain [W]

Zone,Average,Window Frame Heat Loss [W]

Zone,Average,Window Divider Heat Gain [W]

Zone,Average,Window Divider Heat Loss [W]

Zone,Average,Window Frame Inside Temperature [C]

Zone,Average,Window Frame Outside Temperature [C]

Zone,Average,Window Divider Inside Temperature [C]

Zone,Average,Window Divider Outside Temperature [C]

If the user requests to display advanced report variables (e.g. see Output:Diagnostics keyword DisplayAdvancedReportVariables) the the following additional output variables are available for exterior windows and glass doors

Surface Output Variables (all heat transfer surfaces)

Surface Inside Temperature [C]

Surface Outside Temperature [C]

Surface Int Adjacent Air Temperature [C]

The effective bulk air temperature used for modeling the inside surface convection heat transfer. This is the same as the zone mean air temperature when using the mixing model for roomair. However, if more advanced roomair models are used, this variable will report the air temperature predicted by the roomair model as it was used in the surface heat balance model calculations.

Surface Int Convection Coeff [W/m2-K]

Surface Int Convection Heat Rate [W]

Surface Int Convection Heat Rate per Area [W/m2]

The rate of heat transfer from the inside face of the surface to the zone air per unit surface area.

Surface Int Convection Heat Gain to Air [J]

Surface Ext Convection Coeff [W/m2-K]

Surface Ext Convection Heat Rate [W]

The rate of convection heat transfer from the outside face of the surface to the outdoor air.

Surface Ext Convection Heat Rate per Area [W/m2]

The rate of convection heat transfer from the outside face of the surface to the outdoor air per unit surface area.

Surface Ext Convection Heat Loss to Outdoors [J]

The heat transferred from the outside face of the surface to the outdoor air by surface convection heat transfer.

Surface Ext Thermal Radiation Heat Rate [W]

The rate of thermal radiation heat transfer from the outside face of the surface to the outdoor surroundings. This is the net of all forms of longwave thermal infrared radiation heat transfer.

Surface Ext Thermal Radiation Heat Rate per Area [W/m2]

The rate of thermal radiation heat transfer from the outside face of the surface to the outdoor surroundings per unit area. This is the net of all forms of longwave thermal infrared radiation heat transfer.

Surface Ext Thermal Radiation Heat Loss to Outdoors [J]

The heat transferred from the outside face of the surface to the outdoor surroundings by all forms of surface longwave thermal infrared radiation heat transfer.

Surface Ext Rad To Air Coeff [W/m2-K]

Surface Ext Rad To Sky Coeff [W/m2-K]

Surface Ext Rad To Ground Coeff [W/m2-K]

Beam Sol Amount from Ext Windows on Inside of Surface [W]

Beam solar radiation from the exterior windows in a zone incident on the inside face of a surface in the zone. If Solar Distribution in the BUILDING object is equal to MinimalShadowing or FullExterior, it is assumed that all beam solar from exterior windows falls on the floor. In this case the value of this report variable can be greater than zero only for floor surfaces. If Solar Distribution equals FullInteriorExterior the program tracks where beam solar from exterior windows falls inside the zone, in which case the value of this variable can be greater than zero for floor as well as wall surfaces.

Beam Sol Intensity from Ext Windows on Inside of Surface [W/m2]

Beam Sol Amount from Int Windows on Inside of Surface [W]

Beam solar radiation from the interior (i.e., interzone) windows in a zone incident on the inside face of a surface in the zone. This value is calculated only if Solar Distribution in the BUILDING object is equal to FullInteriorExterior. However, the program does not track where this radiation falls. Instead, it is treated by the program as though it were diffuse radiation uniformly distributed over all of the zone surfaces. See Figure 21.

Figure 21. Beam solar radiation entering a zone through an interior window is distributed inside the zone as though it were diffuse radiation.

Beam Sol Intensity from Int Windows on Inside of Surface [W/m2]

The previous variable divided by the surface’s area. Since this diffuse radiation is assumed to be uniformly distributed, the value of this report variable will be the same for all of the heat transfer surfaces in a zone.

Initial Transmitted Diffuse Solar Absorbed on Inside of Surface [W]

As of Version 2.1, diffuse solar transmitted through exterior and interior windows is no longer uniformly distributed. Instead, it is distributed according to the approximate view factors between the transmitting window and all other heat transfer surfaces in the zone. This variable is the amount of transmitted diffuse solar that is initially absorbed on the inside of each heat transfer surface. The portion of this diffuse solar that is reflected by all surfaces in the zone is subsequently redistributed uniformly to all heat transfer surfaces in the zone, along with interior reflected beam solar and shortwave radiation from lights. The total absorbed shortwave radiation is given by the next variable.

Total Shortwave Radiation Absorbed on Inside of Surface [W]

As of Version 2.1, the previous variable plus absorbed shortwave radiation from uniformly distributed initially-reflected diffuse solar, reflected beam solar, and shortwave radiation from lights.

Surface Output Variables (exterior heat transfer surfaces)

Surface Ext Outdoor Dry Bulb [C]

The outdoor air dry-bulb temperature calculated at the height above ground of the surface centroid.

Surface Ext Outdoor Wet Bulb [C]

The outdoor air wet-bulb temperature calculated at the height above ground of the surface centroid.

Surface Ext Wind Speed [m/s]

The outdoor wind speed calculated at the height above ground of the surface centroid.

Surface Ext Sunlit Area [m2]

The outside area of an exterior surface that is illuminated by (unreflected) beam solar radiation.

Surface Ext Sunlit Fraction []

The fraction of the outside area of an exterior surface that is illuminated by (unreflected) beam solar radiation. Equals Surface Ext Sunlit Area divided by total surface area.

Surface Ext Solar Incident [W/m2]

The total solar radiation incident on the outside of an exterior surface. It is the sum of:

Surface Ext Solar Beam Incident
Surface Ext Solar Sky Diffuse Incident
Surface Ext Solar Ground Diffuse Incident
Surface Ext Solar From Sky Diffuse Refl From Obstructions
Surface Ext Beam Sol From Bm-To-Bm Refl From Obstructions
Surface Ext Diff Sol From Bm-To-Diff Refl FromObstructions

Surface Ext Solar Beam Incident [W/m2]

The solar beam radiation incident on the outside of an exterior surface, including the effects of shadowing, if present. The beam here is that directly from the sun; it excludes beam specularly reflected from obstructions.

Surface Ext Solar Sky Diffuse Incident [W/m2]

The solar diffuse radiation from the sky incident on the outside of an exterior surface, including the effects of shadowing, if present.

Surface Ext Solar Ground Diffuse Incident [W/m2]

The solar diffuse radiation incident on the outside of an exterior surface that arises from reflection of beam solar and sky diffuse solar from the ground. This is the sum of the next two output variables, “Surface Ext Diff Sol From Bm-To-Diff Refl From Ground” and “Surface Ext Solar From Sky Diffuse Refl From Ground.” The reflected solar radiation from the ground is assumed to be diffuse and isotropic (there is no specular component).

If “Reflections” option is not chosen in the Solar Distribution Field in the BUILDING object, the effects of shadowing are accounted for by the user-specified value of View Factor to Ground for the surface. If “Reflections” option is chosen, the program determines the effects of shadowing, including time-varying shadowing of the ground plane by the building itself.

Surface Ext Solar From Bm-To-Diff Refl From Ground [W/m2]

The solar diffuse radiation incident on the outside of an exterior surface that arises from beam-to-diffuse reflection from the ground. It is assumed that there is no beam-to-beam (specular) component. The beam here is that directly from the sun; it excludes beam specularly reflected from obstructions.

Surface Ext Solar From Sky Diffuse Refl From Ground [W/m2]

The solar diffuse radiation incident on the outside of an exterior surface that arises from sky diffuse solar reflection from the ground. The sky diffuse here is that directly from the sky; it excludes reflection of sky diffuse from obstructions.

Surface Ext Solar From Sky Diffuse Refl From Obstructions [W/m2]

The solar diffuse radiation incident on the outside of an exterior surface that arises from sky diffuse reflection from one or more obstructions. This value will be non-zero only if “Reflections” option is chosen in the BUILDING object.

Surface Ext Beam Sol From Bm-To-Bm Refl From Obstructions [W/m2]

The solar beam radiation incident on the outside of an exterior surface that arises from beam-to-beam (specular) reflection from one or more obstructions. This value will be non-zero only if “Reflections” option is chosen in the BUILDING object. For windows, the program treats this beam radiation as diffuse radiation in calculating its transmission and absorption.

Surface Ext Diff Sol From Bm-To-Diff Refl FromObstructions [W/m2]

The solar diffuse radiation incident on the outside of an exterior surface that arises from beam-to-diffuse reflection from building shades or building surfaces. This value will be non-zero only if “Reflections” option is chosen in the BUILDING object.

Surface Ext Solar Beam Cosine Of Incidence Angle []

The cosine of the angle of incidence of (unreflected) beam solar radiation on the outside of an exterior surface. The value varies from 0.0 for beam parallel to the surface (incidence angle = 90^O) to 1.0 for beam perpendicular to the surface (incidence angle = 0^O). Negative values indicate the sun is behind the surface, i.e the surface does not see the sun.

Surface Anisotropic Sky Multiplier []

This is the view factor multiplier for diffuse sky irradiance on exterior surfaces taking into account the anisotropic radiance of the sky. The diffuse sky irradiance on a surface is given by Anisotropic Sky Multipler * Diffuse Solar Irradiance.

Opaque Surface Output Variables

The following variables apply only to opaque surfaces, where an opaque surface is considered here to be an exterior or interzone heat transfer surface of class FLOOR, WALL, ROOF or DOOR. Note – these are advanced variables – you must read the descriptions and understand before use – then you must use the Output:Diagnostics object to allow reporting.

Opaque Surface Inside Face Conduction [W]

The heat flow by conduction at the inside face of an opaque heat transfer surface. A positive value means that the conduction is from just inside the inside face to the inside face. A negative value means that the conduction is from the inside face into the surface.

Note that Inside Face Conduction, when positive, does not indicate the heat flow from the surface to the zone air, which is governed by the inside face convection coefficient and the difference in temperature between the inside face and the zone air.

Opaque Surface Inside Face Conduction Gain [W]

The Opaque Surface Inside Face Conduction when that conduction is positive (see definition of Opaque Surface Inside Face Conduction).

Opaque Surface Inside Face Conduction Loss [W]

The absolute value of the Opaque Surface Inside Face Conduction when that conduction is negative (see definition of Opaque Surface Inside Face Conduction).

Zone Opaque Surface Inside Face Conduction Gain [W]

The sum of the Opaque Surface Inside Face Conduction values for all opaque surfaces in a zone when that sum is positive. For example, assume a zone has six opaque surfaces with Opaque Surface Inside Face Conduction values of 100, -200, 400, 50, 150 and –300 W. Then Zone Opaque Surface Inside Face Conduction Gain = 700 - 500 = 200 W.

Zone Opaque Surface Inside Face Conduction Loss [W]

The absolute value of the sum of the Opaque Surface Inside Face Conduction values for all opaque surfaces in a zone when that sum is negative. For example, assume a zone has six opaque surfaces with Opaque Surface Inside Face Conduction values of -100, -200, 400,
-50, 150 and –300W. Then Zone Opaque Surface Inside Face Conduction Loss = |550 – 650| = |-100| = 100 W.

Opaque Surface Inside Face Beam Solar Absorbed [W]

Beam solar radiation from exterior windows absorbed on the inside face of an opaque heat transfer surface. For Solar Distribution = FullInteriorAndExterior, this quantity can be non-zero for both floor and wall surfaces. Otherwise, for Solar Distribution = FullExterior or MinimalShadowing, it can be non-zero only for floor surfaces since in this case all entering beam solar is assumed to fall on the floor. Note that this variable will not be operational (have a real value) unless there are exterior windows in the zone.

Window Output Variables

The following output variables apply to subsurfaces that are windows or glass doors. These two subsurface types are called “window” here. “Exterior window” means that the base surface of the window is an exterior wall, floor, roof or ceiling (i.e., the base surface is a BuildingSurface:Detailed with OutsideFaceEnvironment = ExteriorEnvironment). “Interior window” means that the base surface of the window is an inter-zone wall, floor or ceiling. “Glass” means a transparent solid layer, usually glass, but possibly plastic or other transparent material. “Shading device” means an interior, exterior or between-glass shade or blind, or an exterior screen (only exterior windows can have a shading device).

Zone Transmitted Solar [W]

Zone Transmitted Solar Energy [J]

Zone Window Heat Gain [W]

Zone Window Heat Gain Energy [J]

The sum of the heat flow from all of the exterior windows in a zone when that sum is positive. (See definition of “heat flow” under “Window Heat Gain,” below.)

Zone Window Heat Loss [W]

Zone Window Heat Loss Energy [J]

The absolute value of the sum of the heat flow from all of the exterior windows in a zone when that sum is negative.

Window Solar Absorbed: All Glass Layers [W]

Window Solar Absorbed: All Glass Layers Energy[J]

The total exterior beam and diffuse solar radiation absorbed in all of the glass layers of an exterior window.

Window Solar Absorbed: Shading Device[W] and
Window Solar Absorbed: Shading Device Energy[J]The exterior beam and diffuse solar radiation absorbed in the shading device, if present, of an exterior window.

Window Transmitted Solar [W] and Window Transmitted Solar Energy[J]

The amount of beam and diffuse solar radiation entering a zone through an exterior window. It is the sum of the following two variables, “Window Transmitted Beam Solar” and “Window Transmitted Diffuse Solar.”

Window Transmitted Beam Solar [W]

Window Transmitted Beam Solar Energy[J]

The solar radiation transmitted by an exterior window whose source is beam solar incident on the outside of the window. For a bare window, this transmitted radiation consists of beam radiation passing through the glass (assumed transparent) and diffuse radiation from beam reflected from the outside window reveal, if present. For a window with a shade, this transmitted radiation is totally diffuse (shades are assumed to be perfect diffusers). For a window with a blind, this transmitted radiation consists of beam radiation that passes between the slats and diffuse radiation from beam-to-diffuse reflection from the slats. For a window with a screen, this value consists of direct beam radiation that is transmitted through the screen (gaps between the screen material) and diffuse radiation from beam-to-diffuse reflection from the screen material.

Window Transmitted Beam Solar = Window Transmitted Beam-to-Beam Solar + Window Transmitted Beam-to-Diffuse Solar

Window Transmitted Beam Solar Energy = Window Transmitted Beam-to-Beam Solar Energy + Window Transmitted Beam-to-Diffuse Solar Energy

Window Transmitted Beam-to-Beam Solar [W]

Window Transmitted Beam-to-Beam Solar Energy[J]

For a window with a blind, this transmitted radiation consists of beam radiation that passes between the slats. For a window with a screen, this value consists of direct beam radiation that is transmitted through the screen (gaps between the screen material).

Window Transmitted Beam-to-Diffuse Solar [W]

Window Transmitted Beam-to-Diffuse Solar Energy[J]

For a window with a blind, this transmitted radiation consists of diffuse radiation reflected from beam by the slats. For a window with a screen, this value consists of diffuse radiation reflected by the screen material.

Zone Beam Solar from Exterior Windows [W]

Zone Beam Solar from Exterior Windows Energy[J]

The sum of the Window Transmitted Beam Solar (see definition above) from all exterior windows in a zone.

Zone Beam Solar from Interior Windows [W]

Zone Beam Solar from Interior Windows Energy[J]

The sum of the Window Transmitted Beam Solar (see definition above) from all interior windows in a zone.

Window Transmitted Diffuse Solar [W]

Window Transmitted Diffuse Solar Energy[J]

The solar radiation transmitted by an exterior window whose source is diffuse solar incident on the outside of the window. For a bare window, this transmitted radiation consists of diffuse radiation passing through the glass. For a window with a shade, this transmitted radiation is totally diffuse (shades are assumed to be perfect diffusers). For a window with a blind, this transmitted radiation consists of diffuse radiation that passes between the slats and diffuse radiation from diffuse-to-diffuse reflection from the slats. For a window with a screen, this value consists of diffuse radiation transmitted through the screen (gaps between the screen material) and diffuse radiation from diffuse-to-diffuse reflection from the screen material.

Zone Diff Solar from Exterior Windows [W]

Zone Diff Solar from Exterior Windows Energy[J]

The combined beam and diffuse solar that first entered adjacent zones through exterior windows in the adjacent zones, was subsequently reflected from interior surfaces in those zones (becoming diffuse through that reflection), and was then transmitted through interior windows into the current zone.

Zone Diffuse Solar from Interior Windows [W]

Zone Diffuse Solar from Interior Windows Energy[J]

The sum of the Window Transmitted Diffuse Solar (see definition above) from all interior windows in a zone.

Window System Solar Transmittance []

Effective solar transmittance of an exterior window, including effect of shading device, if present. Equal to “Window Transmitted Solar” divided by total exterior beam plus diffuse solar radiation incident on the window (excluding frame, if present).

Window System Solar Absorptance []

Effective solar absorptance of an exterior window, including effect of shading device, if present. Equal to “Window Solar Absorbed: All Glass Layers” plus “Window Solar Absorbed: Shading Device” divided by total exterior beam plus diffuse solar radiation incident on window (excluding frame, if present)

Window System Solar Reflectance []

Effective solar reflectance of an exterior window, including effect of shading device, if present. Equal to: [1.0 – “Window System Solar Transmittance” – “Window System Solar Absorptance”].

Window Gap Convective Heat Flow [W]

Window Gap Convective Heat Flow Energy[J]

For an airflow window, the forced convective heat flow from the gap through which airflow occurs. This is the heat gained (or lost) by the air from the glass surfaces (and between-glass shading device surfaces, if present) that the air comes in contact with as it flows through the gap. If the gap airflow goes to the zone indoor air, the gap convective heat flow is added to the zone load. Applicable to exterior windows only.

Window Heat Gain [W]

Window Heat Gain Energy[J]

The total heat flow to the zone from the glazing, frame and divider of an exterior window when the total heat flow is positive.

[Window transmitted solar (see definition, above)]
+ [Convective heat flow to the zone from the zone side of the glazing]
+ [Net IR heat flow to the zone from zone side of the glazing]
– [Short-wave radiation from zone transmitted back out the window]
+ [Conduction to zone from window frame and divider, if present]

Here, short-wave radiation is that from lights and diffuse interior solar radiation.

+ [Convective heat flow to the zone from the air flowing through the gap between glazing and shading device]

+ [Convective heat flow to the zone from the zone side of the shading device]
+ [Net IR heat flow to the zone from the zone side of the glazing]
+ [Net IR heat flow to the zone from the zone side of the shading device]
– [Short-wave radiation from zone transmitted back out the window]

The total window heat flow can also be thought of as the sum of the solar and conductive gain from the window glazing.

Window Heat Loss [W]

Window Heat Loss Energy[J]

The absolute value of the total heat flow through an exterior window when the total heat flow is negative. (See definition of “total heat flow” under “Window Heat Gain,” above.)

Glass Beam-Beam Solar Transmittance []

The fraction of exterior beam solar radiation incident on the glass of an exterior window that is transmitted through the glass assuming that the window has no shading device. Takes into account the angle of incidence of beam solar radiation on the glass. Currently, all glass is considered to be transparent, so that incident beam solar is transmitted only as beam solar with no diffuse solar component.

Glass Diffuse-Diffuse Solar Transmittance []

The fraction of exterior diffuse solar radiation incident on the glass of an exterior window that is transmitted through the glass assuming that the window has no shading device. It is assumed that incident diffuse solar is transmitted only as diffuse with no beam component.

Window Calculation Iterations []

The number of iterations needed by the window-layer heat balance solution to converge.

Solar Horizontal Profile Angle [degrees]

For a vertical exterior window, this is an angle appropriate for calculating beam solar quantities appropriate to horizontal window elements such as horizontal reveal surfaces, horizontal frame and divider elements and horizontal slats of window blinds. It is defined as the angle between the window outward normal and the projection of the sun’s ray on the vertical plane containing the outward normal. See Figure 22.

For an exterior window of arbitrary tilt, it is defined as the angle between the window outward normal the projection of the sun’s ray on the plane that contains the outward normal and is perpendicular to the ground.

If the sun is behind the window, the horizontal profile angle is not defined and is reported as 0.0.

Note that in most texts what we call “horizontal profile angle” is called “vertical profile angle.”

Solar Vertical Profile Angle [degrees]

For a vertical exterior window, this is an angle appropriate for calculating beam solar quantities appropriate to vertical window elements such as vertical reveal surfaces, vertical frame and divider elements and vertical slats of window blinds. It is defined as the angle between the window outward normal and the projection of the sun’s ray on the horizontal plane containing the outward normal. See Figure 22.

If the sun is behind the window, the vertical profile angle is not defined and is reported as 0.0.

Note that in most texts what we call “vertical profile angle” is called “horizontal profile angle.”

Figure 22. Vertical exterior window showing solar horizontal profile angle, solar vertical profile angle and solar incidence angle.

Beam Solar Reflected by Outside Reveal Surfaces [W]

Beam solar radiation reflected from the outside reveal surfaces of an exterior window (ref: Reveal Surfaces under WindowProperty:FrameAndDivider).

Beam Solar Reflected by Inside Reveal Surfaces [W]

Beam solar radiation reflected from the inside reveal surfaces of an exterior window (ref: Reveal Surfaces under WindowProperty:FrameAndDivider).

Inside Glass Condensation Flag []

A value of 1 means that moisture condensation will occur on the innermost glass face of an exterior window (i.e., on the glass face in contact with the zone air). Otherwise the value is 0. The condition for condensation is glass inside face temperature < zone air dewpoint temperature.

For airflow exterior windows, in which forced air passes between adjacent glass faces in double- and triple-pane windows, a value of 1 means that condensation will occur on one or both of the glass faces in contact with the airflow. In this case the condition for condensation is:

n For airflow source = indoorair, temperature of either face in contact with airflow < zone air dewpoint temperature.

n For airflow source = outdoorair, temperature of either face in contact with airflow < outside air dewpoint temperature.

As for regular windows, the value will also be 1 if condensation occurs on the innermost glass face.

Inside Frame Condensation Flag []

If an exterior window has a frame and the value of this flag is 1, condensation will occur on the inside surface of the frame. The condition for condensation is frame inside surface temperature < zone air dewpoint temperature.

Inside Divider Condensation Flag []

If an exterior window has a divider and the value of this flag is 1, condensation will occur on the inside surface of the divider. The condition for condensation is divider inside surface temperature < zone air dewpoint temperature.

Fraction of Time Shading Device Is On []

The fraction of time that a shading device is on an exterior window. For a particular simulation timestep, the value is 0.0 if the shading device is off (or there is no shading device) and the value is 1.0 if the shading device is on. (It is assumed that the shading device, if present, is either on or off for the entire timestep.) If the shading device is switchable glazing, a value of 0.0 means that the glazing is in the unswitched (light colored) state, and a value of 1.0 means that the glazing is in the switched (dark colored) state.

For a time interval longer a timestep, this is the fraction of the time interval that the shading device is on. For example, take the case where the time interval is one hour and the timestep is 10 minutes. Then if the shading device is on for two timesteps in the hour and off for the other four timesteps, then the fraction of time that the shading device is on = 2/6 = 0.3333.

Window Blind Slat Angle [deg]

For an exterior window with a blind, this is the angle in degrees between the glazing outward normal and the blind slat angle outward normal, where the outward normal points away from the front face of the slat. The slat angle varies from 0 to 180 deg. If the slat angle is 0 deg or 180 deg, the slats are parallel to the glazing and the slats are said to be “closed”. If the slat angle is 90 deg, the slats are perpendicular to the glazing and the slats are said to be “fully open”. See illustrations under WindowMaterial:Blind. For blinds with a fixed slat angle, the value reported here will be constant.

Blind Beam-Beam Solar Transmittance []

For an exterior window with a blind, this is the fraction of exterior beam solar radiation incident on the blind that is transmitted through the blind as beam solar radiation when the blind is isolated (i.e., as though the window glass were not present). Depends on various factors, including slat angle, width, separation, and thickness, and horizontal solar profile angle (for blinds with horizontal slats) or vertical solar profile angle (for blinds with vertical slats). The transmittance value reported here will be non-zero only when some beam solar can pass through the blind without hitting the slats.

Blind Beam-Diffuse Solar Transmittance []

For an exterior window with a blind, the fraction of exterior beam solar radiation incident on the blind that is transmitted through the blind as diffuse solar radiation when the blind is isolated (i.e., as though the window glass were not present). Depends on various factors, including slat angle, width, separation, thickness and reflectance, and horizontal solar profile angle (for blinds with horizontal slats) or vertical solar profile angle (for blinds with vertical slats).

Blind Diffuse-Diffuse Solar Transmittance []

For an exterior window with a blind, the fraction of exterior diffuse solar radiation incident on the blind that is transmitted through the blind as diffuse solar radiation when the blind is isolated (i.e., as though the window glass were not present). Depends on various factors, including slat angle, width, separation, thickness and reflectance. For blinds with a fixed slat angle the transmittance value reported here will be constant.

Blind/Glass System Beam-Beam Solar Transmittance []

The fraction of exterior beam solar radiation incident on an exterior window with a blind (excluding window frame, if present) that is transmitted through the blind/glass system as beam solar radiation. Depends on various factors, including type of glass; solar incidence angle; slat angle, width, separation, and thickness; and horizontal solar profile angle (for blinds with horizontal slats) or vertical solar profile angle (for blinds with vertical slats).

Blind/Glass System Diffuse-Diffuse Solar Transmittance []

The fraction of exterior diffuse solar radiation incident on an exterior window with a blind (excluding window frame, if present) that is transmitted through the blind/glass system as diffuse solar radiation. Depends on various factors, including type of glass and slat angle, width, separation, thickness and reflectance. For blinds with a fixed slat angle the transmittance value reported here will be constant.

Screen Beam-Beam Solar Transmittance[]

For an exterior window with a screen, this is the fraction of exterior beam solar radiation incident on the screen that is transmitted through the screen as beam solar radiation when the screen is isolated (i.e., as though the window glass were not present). Depends on various factors, including the screen reflectance and the relative angle of the incident beam with respect to the screen. This value will include the amount of inward reflection of solar beam off the screen material surface if the user specifies this modeling option (i.e., Material: WindowScreen, field Reflected Beam Transmittance Accounting Method = Model as Direct Beam).

Screen Beam-Diffuse Solar Transmittance[]

For an exterior window with a screen, the fraction of exterior beam solar radiation incident on the screen that is transmitted through the screen as diffuse solar radiation when the screen is isolated (i.e., as though the window glass were not present). Depends on various factors, including the screen reflectance and the relative angle of the incident beam with respect to the screen. This value is the amount of inward reflection of solar beam off the screen material surface if the user specifies this modeling option (i.e., Material: WindowScreen, field Reflected Beam Transmittance Accounting Method = Model as Diffuse); otherwise, this value will be zero.

Screen Diffuse-Diffuse Solar Transmittance[]

For an exterior window with a screen, the fraction of exterior diffuse solar radiation incident on the screen that is transmitted through the screen as diffuse solar radiation when the screen is isolated (i.e., as though the window glass were not present). Depends on various factors including screen material geometry and reflectance. This value is calculated as an average, constant For a window with a screen, this value consists of diffuse radiation transmitted through the screen (gaps between the screen material) and diffuse radiation from diffuse-to-diffuse reflection from the screen material. For a window with a screen, this value consists of diffuse radiation transmitted through the screen (gaps between the screen material) and diffuse radiation from diffuse-to-diffuse reflection from the screen material.

Screen/Glass System Beam-Beam Solar Transmittance[]

The fraction of exterior beam solar radiation incident on an exterior window with a screen (excluding window frame, if present) that is transmitted through the screen/glass system as beam solar radiation. Depends on various factors, including the screen reflectance and the relative angle of the incident beam with respect to the screen. This value will include the amount of inward reflection of solar beam off the screen material surface if the user specifies this modeling option (i.e., Material: WindowScreen, field Reflected Beam Transmittance Accounting Method = Model as Direct Beam).

Screen/Glass System Diffuse-Diffuse Solar Transmittance []

The fraction of exterior diffuse solar radiation incident on an exterior window with a screen (excluding window frame, if present) that is transmitted through the screen/glass system as diffuse solar radiation. Depends on various factors including screen material geometry and reflectance.

Beam Solar Transmitted Through Interior Window [W]

The beam solar radiation transmitted through an interior window. Calculated only if Solar Distribution = FullInteriorAndExterior in your Building input. The origin of this radiation is beam solar that enters through an exterior window in a zone and then passes through an interior window into the adjacent zone. The amount of this radiation depends on several factors, including sun position, intensity of beam solar incident on the exterior window (including effects of shadowing, if present), relative position of the exterior and interior window, and the size and transmittance of the windows. Note that if there are two or more exterior windows in a zone, then beam solar from one or more of them may pass through the same interior window. Likewise, if there are more than two or more interior windows in a zone then beam solar from a single exterior window may pass through one or more of the interior windows.

Storm Window On/Off Flag [ ]

Indicates whether a storm window glass layer is present (ref: StormWindow). The value is 0 if the storm window glass layer is off, 1 if it is on, and –1 if the window does not have an associated storm window. Applicable only to exterior windows and glass doors.

Initial Transmitted Diffuse Solar Transmitted out through Inside of Window Surface [W]

As of Version 2.1, the diffuse solar transmitted through exterior windows that is initially distributed to another window in the zone and transmitted out of the zone through that window. For exterior windows, this transmitted diffuse solar is “lost” to the exterior environment For interior windows, this transmitted diffuse solar is distributed to heat transfer surfaces in the adjacent zone, and is part of the Initial Transmitted Diffuse Solar Absorbed on Inside of Surface for these adjacent zone surfaces.

Additional Window Outputs (Advanced)

The following output variables for windows or glass doors are available when the user requests to display advanced report variables. These seven reports show the individual components that are combined to determine overall Window Heat Gain and/or Window Heat Loss (described above).

Window Convection Heat Gain from Glazing to Zone [W]

The surface convection heat transfer from the glazing to the zone in watts. This report variable is the term called “[Convective heat flow to the zone from the zone side of the glazing]” under the description above for Window Heat Gain report variable. If the window has an interior shade or blind, then this is zero and the glazing’s convection is included in the report called “Window Convection Heat Gain from Gap between Shade and Glazing to Zone”.

Window Net Infrared Heat Gain from Glazing to Zone [W]

The net exchange of infrared radiation heat transfer from the glazing to the zone in watts. This report variable is the term called “[Net IR heat flow to the zone from zone side of the glazing]” under the description above for Window Heat Gain report variable.

Window Shortwave Heat Loss from Zone Back Out Window [W]

This is the short-wave radiation heat transfer from the zone back out the window in watts. This is a measure of the diffuse short-wave light (from reflected solar and electric lighting) that leave the zone through the window. This report variable is the term called “[Short-wave radiation from zone transmitted back out the window]” under the description above for Window Heat Gain report variable.

Window Heat Gain from Frame and Divider to Zone [W]

This is the heat transfer from any frames and/or dividers to the zone in watts. This report variable is the term called “[Conduction to zone from window frame and divider, if present]” under the description above for Window Heat Gain report variable. (The word “conduction” here is used because the models is simplified compared to the complexities of surface convection and radiation.)

Window Frame Heat Gain [W]

This is the positive heat flow from window frames to the zone in watts. This is part of the Window Heat Gain from Frame and Divider to Zone.

Window Frame Heat Loss [W]

This is the negative heat flow from window frames to the zone in watts. This is part of the Window Heat Gain from Frame and Divider to Zone.

Window Frame Inside Temperature [C]

Window Frame Outside Temperature [C]

Window Divider Heat Gain [W]

This is the positive heat flow from window dividers to the zone in watts. This is part of the Window Heat Gain from Frame and Divider to Zone.

Window Divider Heat Loss [W]

This is the negative heat flow from window dividers to the zone in watts. This is part of the Window Heat Gain from Frame and Divider to Zone.

Window Divider Inside Temperature [C]

Window Divider Outside Temperature [C]

Window Convection Heat Gain from Gap between Shade and Glazing to Zone [W]

This is the convection surface heat transfer from the both the glazing and the shade’s back face to the zone in Watts. This report variable is the term called “[Convective heat flow to the zone from the air flowing through the gap between glazing and shading device]” under the description above for Window Heat Gain report variable.

Window Convection Heat Gain from Shade to Zone [W]

This is the convection surface heat transfer from the front side of any interior shade or blind to the zone in Watts. This report variable is the term called “[Convective heat flow to the zone from the zone side of the shading device]” under the description above for Window Heat Gain report variable.

Window Net Infrared Heat Gain from Shade to Zone [W]

The net exchange of infrared radiation heat transfer from the shade or blind to the zone in watts. This report variable is the term called “[Net IR heat flow to the zone from the zone side of the shading device]” under the description above for Window Heat Gain report variable.

Thermochomic Window Outputs

Window Thermochromic Layer Temperature [C]

Window Thermochromic Layer Specification Temperature [C]

The temperature under which the optical data of the TC glass layer are specified.

The overall properties (U-factor/SHGC/VT) of the thermochromic windows at different specification temperatures are reported in the .eio file. These window constructions are created by EnergyPlus during run time. They have similar names with suffix “_TC_XX” where XX represents a specification temperature.

Switchable Window Outputs

Switchable Window System Switching Factor[]

The switching factor (tint level) of the switchable window: 0 means no switching – clear state; 1 means fully switched – dark state.

Switchable Window System Visible Transmittance[]

Other Surface Outputs/Reports

Several reports can be selected for Surfaces. (See Group – Report for details on how to specify). Examples are:

DXF

This report produces a special file (eplusout.dxf) in the industry standard DXF (Drawing Interchange Format) for drawings. It is produced and accepted by many popular, commercial CAD programs. Detailed reference can be found on the AutoCAD™ website at: http://www.autodesk.com/techpubs/autocad/acadr14/dxf/index.htm

Details, Vertices, DetailsWithVertices

This version of the report creates lines in the eplusout.eio file for each surface (except internal mass surfaces). Details of this reporting is shown in the Output Details and Examples document.

Shading Surfaces

Shading surfaces are entities outside of the building that may cast shadows on the building’s heat transfer surfaces. These entities do not typically have enough thermal mass to be described as part of the building’s thermal makeup.

The most important effect of shading surfaces is to reduce solar gain in windows that are shadowed. (However, in some cases, shading surfaces can reflect solar onto a wall or window and increase solar gain.)

There are two kinds of shading surfaces in EnergyPlus: detached and attached. A detached shading surface, such as a tree or neighboring building, is not connected to the building. An attached shading surface is typically an overhang or fin that is attached to a particular base surface of the building, usually a wall; attached shading surfaces are usually designed to shade specific windows.

Similarly to the surfaces, the detailed objects use vertex entry whereas the other objects are limited to rectangular representation.

EnergyPlus creates “bi-directional” shades from each shading surface entered. This means that the shade you input will cast a shadow no matter which side of the shade the sun is on. For example, a vertical fin will cast a shadow whether the sun is on the left side or right side of the fin.[5]

It is important to note that EnergyPlus will automatically account for “self-shading” effects—such as in L-shaped buildings—in which some of the building’s wall and roof surfaces shade other parts of the building, especially windows. This means that you only need to describe shading elements that aren’t building heat-transfer surfaces.

Shading surfaces can also reflect solar radiation onto the building. This feature is simulated if you choose FullExteriorWithReflections or FullInteriorAndExteriorWithReflections in the Building object (ref: Building - Field: Solar Distribution). In this case, you specify the reflectance properties of a shading surface with the ShadingProperty:Reflectance object .

Shading surfaces also automatically shade diffuse solar radiation (and long-wave radiation) from the sky. And they will automically shade diffuse solar radiation from the ground if Solar Distribution Field = FullExteriorWithReflections or FullInteriorAndExteriorWithReflections in the Building object.[6] Otherwise, shading surfaces will not shade diffuse radiation from the ground unless you enter a reduced value for View Factor to Ground for those building surfaces that are shaded (ref: BuildingSurface:Detailed - Field: View Factor to Ground and FenestrationSurface:Detailed - Field: View Factor to Ground).

Detached Shading Surfaces

Shading:Site, Shading:Building

These objects are used to describe rectangular shading elements that are external to the building. Examples are trees, high fences, near-by hills, and neighboring buildings.

If relative coordinates are used (ref: Field: Coordinate System in GlobalGeometryRules), shading surfaces entered with Shading:Site remain stationary if the building is rotated, whereas those entered with Shading:Building rotate with the building. If world coordinates are used Shading:Site and Shading:Building are equivalent.

Field: Name

This is a unique character string associated with the detached shading surface. Though it must be unique from other surface names, it is used primarily for convenience with detached shading surfaces.

Field: Azimuth Angle

Theoretically, this should face to the surface it is shading (i.e. if a south wall, this should be a north facing shade) but since EnergyPlus automatically generates the mirror image, the facing angle per se’ is not so important.

Field: Tilt Angle

The tilt angle is the angle (in degrees) that the shade is tilted from horizontal (or the ground). Default for this field is 90 degrees.

Starting Corner for the surface

The rectangular surfaces specify the lower left corner of the surface for their starting coordinate. See the introductory paragraph for rules on this entry.

Field: Starting X Coordinate

Field: Starting Y Coordinate

Field: Starting Z Coordinate

Field: Length

Field: Height

Examples of these (can be found in example files 4ZoneWithShading_Simple_1.idf and 4ZoneWithShading_Simple_2.idf)

Shading:Site:Detailed, Shading:Building:Detailed

These objects are used to describe shading elements that are external to the building. Examples are trees, high fences, near-by hills, and neighboring buildings.

If relative coordinates are used (ref: Field: Coordinate System in GlobalGeometryRules), shading surfaces entered with Shading:Site:Detailed remain stationary if the building is rotated, whereas those entered with Shading:Building:Detailed rotate with the building. If world coordinates are used Shading:Site:Detailed and Shading:Building:Detailed are equivalent.

While "detached" implies that shading surfaces are not part of the building, the detached shading sequence can be used to describe attached shading surfaces that may shade heat transfer surfaces in more than one zone. For example, wing A of a building might shade several zones of wing B but wing A (for whatever reason) is not described in the geometry for the simulation so it is represented by a detached shade to get its shadowing effect.

Field: Name

This is a unique character string associated with the detached shading surface. Though it must be unique from other surface names, it is used primarily for convenience with detached shading surfaces.

Field: Transmittance Schedule Name

The name of a schedule of solar transmittance values from 0.0 to 1.0 for the shading surface. If a blank is entered in this field, the transmittance value defaults to 0.0, i.e., the shading surface is opaque at all times. This scheduling can be used to allow for seasonal transmittance change, such as for deciduous trees that have a higher transmittance in winter than in summer. Transmittance based on time of day can also be used—a movable awning, for example, where the transmittance is some value less than 1.0 when the awning is in place and is 1.0 when the awning is retracted.

The following assumptions are made in the shading surface transmittance calculation:

n Beam solar transmittance is independent of angle of incidence on the shading surface.

n Beam radiation incident on a shading surface is transmitted as beam radiation with no change in direction, i.e., there is no beam-to-diffuse component.

n If two shading surfaces with non-zero transmittance overlap, the net transmittance is the product of the individual transmittances. Inter-reflection between the shading surfaces (and between the shading surfaces and the building) is ignored.

n For the daylighting calculation (ref: Group – Daylighting) the shading surface’s visible transmittance is assumed to be the same as its solar transmittance.

n Shading devices are assumed to be opaque to long-wave radiation no matter what the solar transmittance value is.

Note that shading devices only shade solar radiation when the sun is up, which is automatically determined by EnergyPlus from latitude, time of year, etc. The user need only account for the time-varying transmittance of the shading device in the transmittance schedule, not whether the sun is up or not.

Field: Number Vertices

The number of sides in the surface (number of X,Y,Z vertex groups). For further information, see the discussion on “Surface Vertices” above.

Attached Shading Surfaces

Overhangs are usually horizontal devices that are used to shade windows. Fins are usually vertical devices that similarly shade windows.

Shading:Overhang

Field: Name

This is the name of the overhang. It must be different from other surface names.

Field: Window or Door Name

Field: Height above Window or Door

Field Tilt Angle from Window/Door

This field is the tilt angle from the Window/Door. For a flat overhang, this would be 90 (degrees).

Field: Left Extension from Window/Door Width

This field is the width from the left edge of the window/door to the start of the overhang (meters).

Field: Right Extension from Window/Door Width

This field is the width from the right edge of the window/door to the start of the overhang (meters).

Field: Depth

Shading:Overhang:Projection

An overhang typically is used to shade a window in a building. This object allows for specifying the depth of the overhang as a fraction of the window or door’s height.

Field: Name

This is the name of the overhang. It must be different from other surface names.

Field: Window or Door Name

Field: Height above Window or Door

Field Tilt Angle from Window/Door

This field is the tilt angle from the Window/Door. For a flat overhang, this would be 90 (degrees).

Field: Left Extension from Window/Door Width

This field is the width from the left edge of the window/door to the start of the overhang (meters).

Field: Right Extension from Window/Door Width

This field is the width from the right edge of the window/door to the start of the overhang (meters).

Field: Depth as Fraction of Window/Door Height

This field is the fraction of the window/door height to specify as the depth of the overhang (meters) projecting out from the wall.

Shading:Fin

Fins shade either side of windows/doors in a building. This object allows for specification of both fins for the window. Fin placement is relative to the edge of the glass and user must include the frame width when a frame is present.

Field: Name

This is the name of the overhang. It must be different from other surface names.

Field: Window or Door Name

Field: Left Fin Extension from Window/Door

This field is the width from the left edge of the window/door to the plane of the left fin (meters). The extension width is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Left Fin Distance Above Top of Window

This field is the distance from the top of the window to the top of the left fin (meters) and is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Left Fin Distance Below Bottom of Window

This field is the distance from the bottom of the window to the bottom of the left fin (meters) and is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Left Fin Tilt Angle from Window/Door

This field is the tilt angle from the window / door for the left fin. Typically, a fin is 90 degrees (default) from its associated window/door.

Field: Left Fin Depth

This field is the depth (meters) of the left fin (projecting out from the wall).

Field: Right Fin Extension from Window/Door

This field is the width from the right edge of the window/door to the plane of the right fin (meters). The extension width is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Right Fin Distance Above Top of Window

This field is the distance from the top of the window to the top of the right fin (meters) and is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Right Fin Distance Below Bottom of Window

This field is the distance from the bottom of the window to the bottom of the right fin (meters) and is relative to the edge of the glass and includes the frame width.

Field: Right Fin Tilt Angle from Window/Door

This field is the tilt angle from the window / door for the right fin.. Typically, a fin is 90 degrees (default) from its associated window/door.

Field: Right Fin Depth

This field is the depth (meters) of the right fin (projecting out from the wall).

Shading:Fin:Projection

Fins shade either side of windows/doors in a building. This object allows for specification of both fins for the window. This object allows for specifying the depth of the overhang as a fraction of the window or door’s width. Fin placement is relative to the edge of the glass and user must include the frame width when a frame is present.

Field: Name

This is the name of the overhang. It must be different from other surface names.

Field: Window or Door Name

Field: Left Fin Extension from Window/Door

Field: Left Fin Distance Above Top of Window

This field is the distance from the top of the window to the top of the left fin (meters) and is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Left Fin Distance Below Bottom of Window

This field is the distance from the bottom of the window to the bottom of the left fin (meters) and is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Left Fin Tilt Angle from Window/Door

This field is the tilt angle from the window / door for the left fin. Typically, a fin is 90 degrees (default) from its associated window/door.

Field: Left Fin Depth as Fraction of Window/Door Width

This field is the fraction of the window/door width to specify as the depth of the left fin (meters) projecting out from the wall.

Field: Right Fin Extension from Window/Door

This field is the width from the right edge of the window/door to the plane of the right fin (meters).. The extension width is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Right Fin Distance Above Top of Window

This field is the distance from the top of the window to the top of the right fin (meters) and is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Right Fin Distance Below Bottom of Window

This field is the distance from the bottom of the window to the bottom of the right fin (meters) and is relative to the edge of the glass and includes the frame width when a frame is present.

Field: Right Fin Tilt Angle from Window/Door

This field is the tilt angle from the window / door for the right fin.. Typically, a fin is 90 degrees (default) from its associated window/door.

Field: Right Fin Depth as Fraction of Window/Door Width

This field is the fraction of the window/door width to specify as the depth of the right fin (meters) projecting out from the wall.

Examples of these (can be found in example files 4ZoneWithShading_Simple_1.idf and 4ZoneWithShading_Simple_2.idf)

Shading:Zone:Detailed

This object is used to describe attached “subsurfaces” such as overhangs, wings or fins that project outward from a base surface. This classification is used for convenience; actually, a device of this type can cast shadows on the surface to which it is attached as well as on adjacent surfaces. For example, a fin may shade its parent wall as well as adjacent walls.

Note that a zone surface can cast shadows on other zone surfaces. However, you don’t have to worry about such effects—for example, one wall of an L-shaped building shading another wall--because EnergyPlus will automatically check for this kind of “self shadowing” and do the proper calculations.

Unlike attached (or detached) shading surfaces, building surfaces can only cast shadows in the hemisphere towards which they face. This means, for example, that a roof that faces upward will not cast a shadow downward. (Thus, specifying an oversized roof in an attempt to account for the shading effects of overhangs will not work). Interior surfaces do not cast shadows of any kind.

Field: Name

This is the name of the attached shading surface. It must be different from other surface names.

Field: Base Surface Name

This is the name of the surface to which this shading device is attached. This surface can be a wall (or roof) but not a window or door.

Field: Transmittance Schedule Name

The following assumptions are made in the shading surface transmittance calculation:

n Beam solar transmittance is independent of angle of incidence on the shading surface.

n Beam radiation incident on a shading surface is transmitted as beam radiation with no change in direction, i.e., there is no beam-to-diffuse component.

n For the daylighting calculation (ref: Group – Daylighting) the shading surface’s visible transmittance is assumed to be the same as its solar transmittance.

n Shading devices are assumed to be opaque to long-wave radiation no matter what the solar transmittance value is.

Field: Number Vertices

The number of sides in the surface (number of X,Y,Z vertex groups). For further information, see the discussion on “Surface Vertices” above. The example below shows the correct input for an overhang (to shade the appropriate portion of the base wall and window).

ShadingProperty:Reflectance

Specifies the reflectance properties of a shading surface when the solar reflection calculation has requested, i.e., when if “Reflections” option is chosen in the Building object (ref: Building - Field: Solar Distribution). It is assumed that shading surfaces are divided into an unglazed, diffusely reflecting portion and a glazed, specularly-reflecting portion, either of which may be zero. The reflectance properties are assumed to be the same on both sides of the shading surface.

Note that a shadowing transmittance schedule (ref: Shading Surfaces, Field: Transmittance Schedule Name) can be used with a reflective shading surface. However, EnergyPlus assumes that the reflectance properties of the shading surface are constant even if the transmittance varies.

Field: Shading Surface Name

The name of the Shading:Site:Detailed, Shading:Building:Detailed, or Shading:Zone:Detailed object to which the following fields apply.

If this ShadingProperty:Reflectance object is not defined for a shading surface the default values listed in each of the following fields will be used in the solar reflection calculation.

Field: Diffuse Solar Reflectance of Unglazed Part of Shading Surface

The diffuse solar reflectance of the unglazed part of the shading surface (default = 0.2). This reflectance is assumed to be the same for beam-to-diffuse and diffuse-to-diffuse reflection. Beam-to-diffuse reflection is assumed to be independent of angle of incidence of beam radiation. Diffuse-to-diffuse reflection is assumed to be independent of angular distribution of the incident of diffuse radiation. The outgoing diffuse radiation is assumed to be isotropic (hemispherically uniform).

The sum of this reflectance and the shading surface transmittance should be less than or equal to 1.0.

Field: Diffuse Visible Reflectance of Unglazed Part of Shading Surface

The diffuse visible reflectance of the unglazed part of the shading surface (default = 0.2). This reflectance is assumed to be the same for beam-to-diffuse and diffuse-to-diffuse reflection. Beam-to-diffuse reflection is assumed to be independent of angle of incidence of beam radiation. Diffuse-to-diffuse reflection is assumed to be independent of angular distribution of the incident of diffuse radiation. The outgoing diffuse radiation is assumed to be isotropic (hemispherically uniform).

This value if used only for the daylighting calculation (ref: Daylighting:Controls). The sum of this reflectance and the shading surface transmittance should be less than or equal to 1.0.

Field: Fraction of Shading Surface That Is Glazed

The fraction of the area of the shading surface that consists of windows (default = 0.0). It is assumed that the windows are evenly distributed over the surface and have the same glazing construction (see following “Name of Glazing Construction”). This might be the case, for example, for reflection from the façade of a neighboring, highly-glazed building. For the reflection calculation the possible presence of shades, screens or blinds on the windows of the shading surface is ignored. Beam-to-beam (specular) reflection is assumed to occur only from the glazed portion of the shading surface. This reflection depends on angle of incidence as determined by the program from the glazing construction. Beam-to-diffuse reflection from the glazed portion is assumed to be zero. The diffuse-to-diffuse reflectance of the glazed portion is determined by the program from the glazing construction.

Field: Glazing Construction Name

The name of the construction of the windows on the shading surface. Required if Fraction of Shading Surface That Is Glazed is greater than 0.0.

IDF example of Shading Surface Reflectance for shading surface with specular reflection

IDF example of Shading Surface Reflectance for shading surface without specular reflection

WindowProperty:ShadingControl

Window shading with coverings like drapes, blinds, screens or pull-down shades can be used to reduce the amount of solar radiation entering the window or reduce daylighting glare. It can also be used to reduce heat loss through the window (movable insulation). Leaving the window covering open in the winter can maximize solar heat gain and thereby reduce heating loads.

With WindowProperty:ShadingControl—which is referenced by windows and glass doors (ref: FenestrationSurface:Detailed with Type = Window or GlassDoor)--you specify the type and location of the shading device, what variable or combination of variables controls deployment of the shading device, and what the control setpoint is. If the shading device is a blind, you also specify how the slat angle is controlled.

As shown in Figure 24, a shading device can be inside the window (Shading Type = InteriorShade or InteriorBlind), outside the window (Shading Type = ExteriorShade or ExteriorBlind), or between panes of glass (Shading Type = BetweenGlassShade or BetweenGlassBlind). The exception is window screens which can only be outside the window (Shading Type = ExteriorScreen).

When a shading device is present it is either retracted or activated. When it is retracted it covers none of the window. When it is activated it covers the entire glazed part of the window (but not the frame). Whether the shading device is retracted or activated in a particular timestep depends on the control mechanism: see “Shading Control Type,” below. To model a case in which the shading device, when activated, covers only part of the window you will have to divide the window into two separate windows, one with the shading device and one without the shading device.

A shading device can also be of a kind in which the optical properties of the glazing switch from one set of values to another in order to increase or decrease solar or visible transmittance (Shading Type = SwitchableGlazing).

Specify “Name of Construction with Shading”

This is the name of a window Construction that has the shading device as one of its layers. The thermal and solar-optical properties of the shading device are given by the shading material referenced in that Construction (ref: Construction, WindowMaterial:Shade, WindowMaterial:Screen and WindowMaterial:Blind). To use this method you have to define two Constructions for the window, one without the shading device and one with it. See Example 1, below.

The Construction without the shading device is referenced in the FenestrationSurface:Detailed input for the window (see IDF example, below). The Construction with the shading device is referenced by the window’s WindowProperty:ShadingControl.

For Shading Type = InteriorShade, InteriorBlind, ExteriorShade, ExteriorScreen and ExteriorBlind these two Constructions must be identical expect for the presence of the shading layer in the shaded Construction, otherwise you will get an error message. You will also get an error message if the Construction referenced by the window has a shading layer.

Specify the “Material Name of the Shading Device”

This is the name of a WindowMaterial:Shade, WindowMaterial:Screen or WindowMaterial:Blind. This method can be used with Shading Type = InteriorShade, InteriorBlind, ExteriorShade and ExteriorBlind. It cannot be used with Shading Type = BetweenGlassShade, BetweenGlassBlind, or SwitchableGlazing. If Shading Type = InteriorShade or ExteriorShade, then you specify the name of a WindowMaterial:Shade. If Shading Type = InteriorBlind or ExteriorBlind, then you specify the name of a WindowMaterial:Blind. If Shading Type = ExteriorScreen, then you specify the name of a WindowMaterial:Screen. See Example 2, below. This method is simpler to use since you don’t have to specify two Constructions that differ only by the shading layer.

When this method is used, the program will automatically create a shaded window construction by adding a shading layer to the outside or inside of the construction corresponding to the window referencing the WindowProperty:ShadingControl. The name, created by the program, of this shaded construction is composed as follows: if the name of the window construction is CCC and the material name of the shading device is DDD, then the shaded construction name is CCC:DDD:INT for an interior shading device and CCC:DDD:EXT for an exterior shading device.

This method is the required if you want to add a shading device to a construction brought in from a WINDOW5 Data File (ref: Construction:WindowDataFile).

Note that if both “Name of Construction with Shading” and “Material Name of Shading Device” are specified, the former takes precedence.

Most Shading Control Types allow you to specify a schedule that determines when the control is active. One example is a control that is active seasonally. For example, to deploy shading only in the summer when the incident solar is high enough, use Shading Control Type = OnIfHighSolarOnWindow with a schedule that is 1 during the summer months and 0 otherwise and specify Shading Control Is Scheduled = YES.

In addition, most Shading Control Types also allow you to specify that glare control is active in addition to the specified Control Type. For example, you might want to deploy shading when the solar incident on a window is too high OR the glare from the window is too high. This type of joint control requires that the window be in a daylit zone, that the maximum allowed glare be specified in the Daylighting object for the zone, and that Glare Control Is Active = YES in WindowProperty:ShadingControl.

If Shading Type = InteriorBlind, ExteriorBlind or BetweenGlassBlind you can use WindowProperty:ShadingControl to specify how the slat angle of the blind is controlled when the blind is in place.

A special type of WindowProperty:ShadingControl is SwitchableGlazing. An example is electrochromic glazing in which the transmittance and reflectance of the glass is controlled electronically. For example, you could have electrochromic glazing switch from clear (high transmittance) to dark (low transmittance) to control solar gain. If you choose the Shading Type = SwitchableGlazing option for WindowProperty:ShadingControl, the unswitched (clear) state is specified by the Construction referenced by the window and the switched (dark) state is specified by the Construction referenced by WindowProperty:ShadingControl for that window. For example, if you specify Shading Type = SwitchableGlazing and Shading Control Type = OnIfHighSolarOnWindow, then the glazing will switch to the dark state whenever the solar radiation striking the window exceeds the Setpoint value.

For Shading Type = SwitchableGlazing the state of the window is either clear (unswitched) or dark (fully switched) for all Shading Control Types except MeetDaylightIlluminanceSetpoint. In this case, the transmittance of the glazing is adjusted to just meet the daylight illuminance set point at the first daylighting reference point (see Daylighting). This type of control assures that there is just enough solar gain to meet the daylighting requirements in a zone, and no more, thus reducing the cooling load.

Field: Name

Name of the window shading control. It is referenced by a window (ref: Field: Shading Control Name).

Field: Shading Type

InteriorShade: A diffusing shade is on the inside of the window. (In the shaded Construction the shading layer must be a WindowMaterial:Shade.)

ExteriorShade: A diffusing shade is on the outside of the window. (In the shaded Construction the shading layer must be a WindowMaterial:Shade.)

BetweenGlassShade: A diffusing shade is between two glass layers. (In the shaded Construction the shading layer must be a WindowMaterial:Shade.) This shading type is allowed only for double- and triple-glazing. For triple-glazing the shade must be between the two inner glass layers.

ExteriorScreen: An insect screen is on the outside of the window. (In the shaded Construction the shadling layer must be a WindowMaterial:Screen.)

InteriorBlind: A slat-type shading device, such as a Venetian blind, is on the inside of the window. (In the shaded Construction the shading layer must be a WindowMaterial:Blind.)

ExteriorBlind: A slat-type shading device is on the outside of the window. (In the shaded Construction the shading layer must be a WindowMaterial:Blind.)

BetweenGlassBlind: A slat-type shading device is between two glass layers. (In the shaded Construction the shading layer must be a WindowMaterial:Blind.) This shading type is allowed only for double- and triple-glazing. For triple-glazing the blind must be between the two inner glass layers.

SwitchableGlazing: Shading is achieved by changing the characteristics of the window glass, such as by darkening it.

Field: Construction with Shading Name

Name of the window Construction that has the shading in place. The properties of the shading device are given by the shading material referenced in that Construction (ref: Construction, WindowMaterial:Shade, WindowMaterial:Screen and WindowMaterial:Blind). For Shading Type = SwitchableGlazing, this is the name of the Construction that corresponds to the window in its fully-switched (darkest) state.

Specifying “Name of Construction with Shading” is required if Shading Type = BetweenGlassShade, BetweenGlassBlind, or SwitchableGlazing. For other Shading Types, you may alternatively specify “Material Name of Shading Device” (see below).

Field: Shading Control Type

Specifies how the shading device is controlled, i.e., it determines whether the shading device is “on” or “off.” For blinds, screens and shades, when the device is “on” it is assumed to cover all of the window except its frame; when the device is “off” it is assumed to cover none of the window (whether “on” or “off” the shading device is assumed to cover none of the wall that the window is on).

For switchable glazing, “on” means that the glazing is in the fully-switched state and “off” means that it is in the unswitched state; for example, for electrochromic glazing, “on” means the glazing is in its darkest state and “off” means it is in its lightest state.

The choices for Shading Control Type are the following. If SetPoint is applicable its units are shown in parentheses.

The following six control types are used primarily to reduce zone cooling load due to window solar gain.

OnIfScheduleAllows: Shading is on if schedule value is non-zero. Requires that Schedule Name be specified and Shading Control Is Scheduled = Yes.

Note: For exterior window screens AlwaysOn, AlwaysOff, and OnIfScheduleAllows are the only valid shading control types.

OnIfHighSolarOnWindow: Shading is on if beam plus diffuse solar radiation incident on the window exceeds SetPoint (W/m²) and schedule, if specified, allows shading.

OnIfHighHorizontalSolar: Shading is on if total (beam plus diffuse) horizontal solar irradiance exceeds SetPoint (W/m²) and schedule, if specified, allows shading.

OnIfHighOutdoorAirTemperature: Shading is on if outside air temperature exceeds SetPoint (C) and schedule, if specified, allows shading.

OnIfHighZoneAirTemperature: Shading is on if zone air temperature in the previous timestep exceeds SetPoint (C) and schedule, if specified, allows shading.

OnIfHighZoneCooling: Shading is on if zone cooling rate in the previous timestep exceeds SetPoint (W) and schedule, if specified, allows shading.

OnIfHighGlare: Shading is on if the total daylight glare index at the zone’s first daylighting reference point from all of the exterior windows in the zone exceeds the maximum glare index specified in the daylighting input for zone (ref: Group – Daylighting). Applicable only to windows in zones with daylighting.

Note: Unlike other Shading Control Types, glare control is active whether or not a schedule is specified.

MeetDaylightIlluminanceSetpoint: Used only with ShadingType = SwitchableGlazing in zones with daylighting controls. In this case the transmittance of the glazing is adjusted to just meet the daylight illuminance set point at the first daylighting reference point. Note that the daylight illuminance set point is specified in the Daylighting:Controls object for the Zone; it is not specified as a WindowProperty:ShadingControl SetPoint. When the glare control is active, if meeting the daylight illuminance set point at the first daylighting reference point results in higher discomfort glare index (DGI) than the specified zone’s maximum allowable DGI for either of the daylight reference points, the glazing will be further dimmed until the DGI equals the specified maximum allowable value.

The following three control types can be used to reduce zone heating load during the winter by reducing window conductive heat loss at night and leaving the window unshaded during the day to maximize solar gain. They are applicable to any Shading Type except ExteriorScreen but are most appropriate for interior or exterior shades with high insulating value ("movable insulation"). “Night” means the sun is down and “day” means the sun is up.

OnNightIfLowOutdoorTempAndOffDay: Shading is on at night if the outside air temperature is less than SetPoint (C) and schedule, if specified, allows shading. Shading is off during the day.

OnNightIfLowInsideTempAndOffDay: Shading is on at night if the zone air temperature in the previous timestep is less than SetPoint (C) and schedule, if specified, allows shading. Shading is off during the day.

OnNightIfHeatingAndOffDay: Shading is on at night if the zone heating rate in the previous timestep exceeds SetPoint (W) and schedule, if specified, allows shading. Shading is off during the day.

The following two control types can be used to reduce zone heating and cooling load. They are applicable to any Shading Type except ExteriorScreen but are most appropriate for translucent interior or exterior shades with high insulating value ("translucent movable insulation").

OnNightIfLowOutdoorTempAndOnDayIfCooling: Shading is on at night if the outside air temperature is less than SetPoint (C). Shading is on during the day if the zone cooling rate in the previous timestep is non-zero. Night and day shading is subject to schedule, if specified.

OnNightIfHeatingAndOnDayIfCooling: Shading is on at night if the zone heating rate in the previous timestep exceeds SetPoint (W). Shading is on during the day if the zone cooling rate in the previous timestep is non-zero. Night and day shading is subject to schedule, if specified.

The following control types can be used to reduce zone cooling load. They are applicable to any Shading Type except ExteriorScreen but are most appropriate for interior or exterior blinds, interior or exterior shades with low insulating value, or switchable glazing.

OffNightAndOnDayIfCoolingAndHighSolarOnWindow: Shading is off at night. Shading is on during the day if the solar radiation incident on the window exceeds SetPoint (W/m²) and if the zone cooling rate in the previous timestep is non-zero. Daytime shading is subject to schedule, if specified.

OnNightAndOnDayIfCoolingAndHighSolarOnWindow: Shading is on at night. Shading is on during the day if the solar radiation incident on the window exceeds SetPoint (W/m²) and if the zone cooling rate in the previous timestep is non-zero. Day and night shading is subject to schedule, if specified. (This Shading Control Type is the same as the previous one, except the shading is on at night rather than off.)

OnIfHighOutdoorAirTempAndHighSolarOnWindow: Shading is on if the outside air temperature exceeds the Setpoint (C) and if if the solar radiation incident on the window exceeds SetPoint 2 (W/m²).

OnIfHighOutdoorAirTempAndHighHorizontalSolar: Shading is on if the outside air temperature exceeds the Setpoint (C) and if if the horizontal solar radiation on the window exceeds SetPoint 2 (W/m²).

Field: Schedule Name

Required if Shading Control Is Scheduled = Yes. If schedule value > 0 , shading control is active, i.e., shading can be on only if the shading control test passes. If schedule value = 0, shading is off whether or not the control test passes. If Schedule Name is not specified, shading control is assumed to be active at all times.

Field: Setpoint

The setpoint for activating window shading. The units depend on the type of trigger:

SetPoint is unused for Shading Control Type = OnIfScheduleAllows, OnIfHighGlare and DaylightIlluminance.

Field: Shading Control Is Scheduled

Accepts values YES and NO. The default is NO. Not applicable for Shading Control Type = OnIfHighGlare and should be blank in that case.

If YES, Schedule Name is required and that schedule determines whether the shading control specified by Shading Control Type is active or inactive (see Schedule Name, above).

If NO, Schedule Name is not applicable (should be blank) and the shading control is unscheduled.

Shading Control Is Scheduled = YES is required if Shading Control Type = OnIfScheduleAllows.

Field: Glare Control Is Active

If YES and the window is in a daylit zone, shading is on if the zone's discomfort glare index exceeds the maximum discomfort glare index specified in the Daylighting object referenced by the zone. For switchable windows with MeetDaylightIlluminanceSetpoint shading control, if Glare Control is active, the windows are always continuously dimmed as necessary to meet the zone’s maximum allowable DGI while providing appropriate amount of daylight for the zone.

The glare test is OR'ed with the test specified by Shading Control Type. For example, if Glare Control Is Active = YES and Shading Control Type = OnIfHighZoneAirTemp, then shading is on if glare is too high OR if the zone air temperature is too high.

Glare Control Is Active = YES is required if Shading Control Type = OnIfHighGlare.

Field: Shading Device Material Name

The name of a WindowMaterial:Shade, WindowMaterial:Screen or WindowMaterial:Blind. Required if "Name of Construction with Shading" is not specified. Not applicable if Shading Type = BetweenGlassShade, BetweenGlassBlind or SwitchableGlazing and should be blank in this case. If both "Name of Construction with Shading" and "Material Name of Shading Device" are entered the former takes precedence.

Field: Type of Slat Angle Control for Blinds

Applies only to Shading Type = InteriorBlind, ExteriorBlind or BetweenGlassBlind. Specifies how the slat angle is controlled. The choices are FixedSlatAngle, ScheduledSlatAngle and BlockBeamSolar.

If FixedSlatAngle (the default), the angle of the slat is fixed at the value input for the WindowMaterial:Blind that is contained in the construction specified by Name of Construction with Shading or is specified by Material Name of Shading Device.

If ScheduledSlatAngle, the slat angle varies according to the schedule specified by Slat Angle Schedule Name, below.

If BlockBeamSolar, the slat angle is set each timestep to just block beam solar radiation. If there is no beam solar on the window the slat angle is set to the value input for the WindowMaterial:Blind that is contained in the construction specified by Name of Construction with Shading or is specified by Material Name of Shading Device. The BlockBeamSolar option prevents beam solar from entering the window and causing possible unwanted glare if the beam falls on work surfaces while at the same time allowing near-optimal indirect radiation for daylighting.

Field: Slat Angle Schedule Name

This is the name of a schedule of slat angles that is used when Type of Slat Angle Control for Blinds = ScheduledSlatAngle. You should be sure that the schedule values fall within the range given by the Minimum Slat Angle and Maximum Slat Angle values entered in the corresponding WindowMaterial:Blind. If not, the program will force them into this range.

Field: Setpoint 2

Used only as the second setpoint for the following two-setpoint control types: OnIfHighOutdoorAirTempAndHighSolarOnWindow, OnIfHighOutdoorAirTempAndHighHorizontalSolar, OnIfHighZoneAirTempAndHighSolarOnWindow,

An IDF example: window with interior roll shade that is deployed when solar incident on the window exceeds 50 W/m².

! Example 1: Interior movable shade specified by giving name of shaded construction

! in WindowProperty:ShadingControl

WindowMaterial:Glazing, GLASS - CLEAR SHEET 1 / 8 IN, !- Material Name

SpectralAverage,! Optical data type {SpectralAverage or Spectral}

, ! Name of spectral data set when Optical Data Type = Spectral

0.003 , !- Thickness {m}

0.837 , !- Solar Transmittance at Normal Incidence

0.075 , !- Solar Reflectance at Normal Incidence: Front Side

0.075 , !- Solar Reflectance at Normal Incidence: Back Side

0.898 , !- Visible Transmittance at Normal Incidence

0.081 , !- Visible Reflectance at Normal Incidence: Front Side

0.081 , !- Visible Reflectance at Normal Incidence: Back Side

0.0 , !- IR Transmittance

0.8400000 , !- IR Emissivity: Front Side

0.8400000 , !- IR Emissivity: Back Side

0.9000000 ; !- Conductivity {W/m-K}

WindowMaterial:Shade, ROLL SHADE, !- Material Name

0.3 , !- Solar Transmittance at normal incidence

0.5000000 , !- Solar Reflectance (same for front and back side)

0.3 , !- Visible Transmittance at normal incidence

0.5000000 , !- Visible reflectance (same for front and back side)

0.9000000 , !- IR Emissivity (same for front and back side)

0.05 , !- IR Transmittance

0.003 , !- Thickness

0.1 , !- Conductivity {W/m-K}

     0.0          ,   !- Top Opening Multiplier
     0.0          ,   !- Bottom Opening Multiplier
     0.5          ,   !- Left-Side Opening Multiplier
     0.5          ,   !- Right-Side Opening Multiplier
     0.0          ;   !- Air-Flow Permeability

Construction, SINGLE PANE WITH NO SHADE, ! Name of construction without shade

GLASS - CLEAR SHEET 1 / 8 IN; !- First material layer

Construction, SINGLE PANE WITH INT SHADE, ! Name of construction with shade

GLASS - CLEAR SHEET 1 / 8 IN, !- First material layer

ROLL SHADE ; !- Second material layer

WindowProperty:ShadingControl, CONTROL ON INCIDENT SOLAR, !- Name of Shading Control

InteriorShade, !- Shading Type

SINGLE PANE WITH INT SHADE, !- Name of construction with shading device

OnIfHighSolarOnWindow, !- Shading Control Type

, !- Schedule name

50.0, !- Setpoint {W/m2}

NO, !- Shading Control Is Scheduled

NO, !- Glare Control Is Active

, !- Material Name of Shading Device

, !- Type of Slat Angle Control for Blinds

; !- Slat Angle Schedule Name

WindowProperty:FrameAndDivider

The WindowProperty:FrameAndDivider object is referenced by exterior windows that have

A frame surrounds the glazing in a window (see Figure 25 and Figure 26). It is assumed that all frame characteristics—such as width, conductance and solar absorptance—are the same for the top, bottom and side elements of the frame. If the frame elements are not the same then you should enter area-weighted average values for the frame characteristics.

The window vertices that you specify in the FenestrationSurface:Detailed object are those of the glazed part of the window, not the frame. EnergyPlus automatically subtracts the area of the frame—determined from the glazing dimensions and the frame width—from the area of the wall containing the window.

A divider, as shown in Figure 25, Figure 26 and Figure 27, divides the glazing up into separate lites. It is assumed that all divider elements have the same characteristics. If not, area-weighted average values should be used. EnergyPlus automatically subtracts the divider area from the glazed area of the window.

Reveal surfaces, as shown in Figure 28, are associated with the setback of the glazing from the outside and/or inside surface of the parent wall. If the depth and solar absorptance of these surfaces are specified, the program will calculate the reflection of beam solar radiation from these surfaces. The program also calculates the shadowing (onto the window) of beam and diffuse solar radiation by outside reveal surfaces.

In EnergyPlus, a window can have any combination of frame, divider and reveal surfaces, or none of these.

The best source of frame and divider characteristics is the WINDOW 5 program, which will calculate the values required by EnergyPlus for different frame and divider types. In particular, the THERM program within WINDOW 5 will calculate the effective conductance of frames and dividers; this is the conductance taking 2-D heat transfer effects into account.

Note that a window’s frame and divider characteristics, along with other window information, can be read in from the Window 5 Data File (see “Importing Windows from WINDOW 5” and “Construction from Window5 Data File”). In this case the WindowProperty:FrameAndDivider referenced by the window is not applicable and should be blank unless you want to specify reveal surfaces for beam solar reflection.

In the illustration above, the divider has two horizontal elements and one vertical element.

Field: Name

The name of the frame/divider object. It is referenced by WindowProperty:FrameAndDivider Name in FenestrationSurface:Detailed.

Field: Frame Width

The width of the frame elements when projected onto the plane of the window. It is assumed that the top, bottom and side elements of the frame have the same width. If not, an average frame width should be entered such that the projected frame area calculated using the average value equals the sum of the areas of the frame elements.

Field: Frame Outside Projection

The amount by which the frame projects outward from the outside surface of the window glazing. If the outer surface of the frame is flush with the glazing, Frame Outside Projection = 0.0. Used to calculate shadowing of frame onto glass, solar absorbed by frame, IR emitted and absorbed by frame, and convection from frame.

Field: Frame Inside Projection

The amount by which the frame projects inward from the inside surface of the window glazing. If the inner surface of the frame is flush with the glazing, Frame Inside Projection = 0.0. Used to calculate solar absorbed by frame, IR emitted and absorbed by frame, and convection from frame.

Field: Frame Conductance

The effective thermal conductance of the frame measured from inside to outside frame surface (no air films) and taking 2-D conduction effects into account. Obtained from WINDOW 5 or other 2-D calculation.

Field: Ratio of Frame-Edge Glass Conductance to Center-Of-Glass Conductance

The glass conductance near the frame (excluding air films) divided by the glass conductance at the center of the glazing (excluding air films). Used only for multi-pane glazing constructions. This ratio is greater than 1.0 because of thermal bridging from the glazing across the frame and across the spacer that separates the glass panes. Values can be obtained from WINDOW 5 for the user-selected glazing construction and frame characteristics.

Field: Frame Solar Absorptance

The solar absorptance of the frame. The value is assumed to be the same on the inside and outside of the frame and to be independent of angle of incidence of solar radiation. If solar reflectance (or reflectivity) data is available, then absorptance is equal to 1.0 minus reflectance (for opaque materials).

Field: Frame Visible Absorptance

The visible absorptance of the frame. The value is assumed to be the same on the inside and outside of the frame and to be independent of angle of incidence of solar radiation. If visible reflectance (or reflectivity) data is available, then absorptance is equal to 1.0 minus reflectance (for opaque materials).

Field: Frame Thermal Hemispherical Emissivity

The thermal emissivity of the frame, assumed the same on the inside and outside.

Field: Divider Type

The type of divider (see figure below). Divider Type = Suspended is applicable only to multi-pane glazing. It means that the divider is suspended between the panes. (If there are more than two glass layers, the divider is assumed to be placed between the two outermost layers.)

Divider Type = DividedLite means that the divider elements project out from the outside and inside surfaces of the glazing and divide the glazing into individual lites. For multi-pane glazing, this type of divider also has between-glass elements that separate the panes.

Field: Divider Width

The width of the divider elements when projected onto the plane of the window. It is assumed that the horizontal and vertical divider elements have the same width. If not, an average divider width should be entered such that the projected divider area calculated using the average value equals the sum of the areas of the divider elements.

Field: Number of Horizontal Dividers

Field: Number of Vertical Dividers

Field: Divider Outside Projection

The amount by which the divider projects out from the outside surface of the window glazing. For Divider Type = Suspended, Divider Projection = 0.0. Used to calculate shadowing of divider onto glass, solar absorbed by divider, IR emitted and absorbed by divider, and convection from divider.

Field: Divider Inside Projection

The amount by which the divider projects inward from the inside surface of the window glazing. If the inner surface of the divider is flush with the glazing, Divider Inside Projection = 0.0. Used to calculate solar absorbed by divider, IR emitted and absorbed by divider, and convection from divider.

Field: Divider Conductance

The effective thermal conductance of the divider measured from inside to outside divider surface (no air films) and taking 2-D conduction effects into account. Obtained from WINDOW 5/6 or other 2-D calculation.

Field: Ratio of Divider-Edge Glass Conductance to Center-Of-Glass Conductance

The glass conductance near the divider (excluding air films) divided by the glass conductance at the center of the glazing (excluding air films). Used only for multi-pane glazing constructions. This ratio is greater than 1.0 because of thermal bridging from the glazing across the divider and across the spacer that separates the glass panes. Values can be obtained from WINDOW 5/6 for the user-selected glazing construction and divider characteristics.

Field: Divider Solar Absorptance

The solar absorptance of the divider. The value is assumed to be the same on the inside and outside of the divider and to be independent of angle of incidence of solar radiation. If solar reflectance (or reflectivity) data is available, then absorptance is equal to 1.0 minus reflectance (for opaque materials).

Field: Divider Visible Absorptance

The visible absorptance of the divider. The value is assumed to be the same on the inside and outside of the divider and to be independent of angle of incidence of solar radiation. If visible reflectance (or reflectivity) data is available, then absorptance is equal to 1.0 minus reflectance (for opaque materials).

Field: Divider Thermal Hemispherical Emissivity

The thermal emissivity of the divider, assumed the same on the inside and outside.

The following fields specify the properties of the window reveal surfaces (reveals occur when the window is not in the same plane as the base surface). From this information and from the geometry of the window and the sun position, the program calculates beam solar radiation absorbed and reflected by the top, bottom, right and left sides of outside and inside window reveal surfaces. In doing this calculation, the shadowing on a reveal surface by other reveal surfaces is determined using the orientation of the reveal surfaces and the sun position.

n If an exterior shade, screen or blind is in place it shades exterior and interior reveal surfaces so that in this case there is no beam solar on these surfaces.

n If an interior shade or blind is in place it shades the interior reveal surfaces so that in this case there is no beam solar on these surfaces.

n The possible shadowing on inside reveal surfaces by a window divider is ignored.

n The outside reveal surfaces (top, bottom, left, right) have the same solar absorptance and depth. This depth is not input here but is automatically determined by the program—from window and wall vertices--as the distance between the plane of the outside face of the glazing and plane of the outside face of the parent wall.

n The inside reveal surfaces are divided into two categories: (1) the bottom reveal surface, called here the "inside sill;" and (2) the other reveal surfaces (left, right and top).

n The left, right and top inside reveal surfaces have the same depth and solar absorptance. The inside sill is allowed to have depth and solar absorptance values that are different from the corresponding values for the other inside reveal surfaces.

n The inside sill depth is required to be greater than or equal to the depth of the other inside reveal surfaces. If the inside sill depth is greater than zero the depth of the other inside reveal surfaces is required to be greater than zero.

n The reflection of beam solar radiation from all reveal surfaces is assumed to be isotropic diffuse; there is no specular component.

n Half of the beam solar reflected from outside reveal surfaces is goes towards the window; the other half goes back to the exterior environment (i.e., reflection of this outward-going component from other outside reveal surfaces is not considered).

n The half that goes towards the window is added to the other solar radiation incident on the window. Correspondingly, half of the beam solar reflected from inside reveal surfaces goes towards the window, with the other half going into the zone. The portion going towards the window that is not reflected is absorbed in the glazing or is transmitted back out into the exterior environment.

n The beam solar that is absorbed by outside reveal surfaces is added to the solar absorbed by the outside surface of the window's parent wall; similarly, the beam solar absorbed by the inside reveal surfaces is added to the solar absorbed by the inside surface of the parent wall.

The net effect of beam solar reflected from outside reveal surfaces is to increase the heat gain to the zone, whereas the effect of beam solar reflected from inside reveal surfaces is to decrease the heat gain to the zone since part of this reflected solar is transmitted back out the window.

If the window has a frame, the absorption of reflected beam solar by the inside and outside surfaces of the frame is considered. The shadowing of the frame onto interior reveal surfaces is also considered.

Field: Outside Reveal Solar Absorptance

Field: Inside Sill Depth

The depth of the inside sill, measured from the inside surface of the glazing to the edge of the sill (see Figure 28).

Field: Inside Sill Solar Absorptance

The depth of the inside reveal surfaces other than the sill, measured from the inside surface of the glazing to the edge of the reveal surface (see Figure 28).

Field: Inside Reveal Solar Absorptance

Figure 28. (a) Vertical section through a window (with frame) showing outside and inside reveal surfaces and inside sill. (b) Perspective view looking from the outside of a window (without frame) showing reveal surfaces. Note that “Outside Reveal Depth” is not a user input; it is calculated by the program from the window and wall vertices.

WindowProperty:AirflowControl

This object is used to specify the control mechanism for windows in which forced air flows in the gap between adjacent layers of glass. Such windows are called “airflow windows.” They are also known as “heat-extract windows” or “climate windows.”

A common application is to reduce the zone load by exhausting indoor air through the window. In the cooling season this picks up and expels some of the solar heat absorbed by the window glass (and by the between-glass shade or blind, if present). In the heating season this warms the window, reducing the heat loss from the window. A side benefit is increased thermal comfort. This is because the inside surface of the window will generally be cooler in summer and warmer in winter.

The surface report variable “Window Gap Convective Heat Flow [W]” gives the heat picked up (or lost) by the gap airflow.

Field: Name

Name of the window that this WindowProperty:AirflowControl refers to. It must be a window with two or three glass layers, i.e., double- or triple-glazing. For triple-glazing the airflow is assumed to be between the two inner glass layers.

An error will result if the gas in the airflow gap is other than air. If an airflow window has a between-glass shade or blind, the gas in the gap on either side of the shade or blind must be air.

Field: Airflow Source

Field: Airflow Destination

This is where the gap air goes after passing through the window. The choices are:

ReturnAir. The gap air goes to the return air for the window’s zone. This choice is allowed only if Airflow Source = InsideAir. If the return air flow is zero, the gap air goes to the indoor air of the window’s zone. If the sum of the gap airflow for all of the windows in a zone with Airflow Destination = ReturnAir exceeds the return airflow, then the difference between this sum and the return airflow goes to the indoor air.

Figure 29 shows the allowed combinations of Airflow Source and Airflow Destination. The allowed combinations of Airflow Source and Airflow Destination are:

Field: Maximum Flow Rate

The maximum value of the airflow, in m³/s per m of glazing width. The value is typically 0.006 to 0.009 m³/s-m (4 to 6 cfm/ft).

The airflow can be modulated by specifying Airflow Has Multiplier Schedule = Yes and giving the name of the Airflow Multiplier Schedule (see below).

The fan energy used to move the air through the gap is generally very small and so is ignored.

Field: Airflow Control Type

ScheduledOnly. The airflow in a particular timestep equals Maximum Airflow times the value of the Airflow Multiplier Schedule for that timestep.

Field: Airflow Is Scheduled

Field: Airflow Multiplier Schedule Name

The name of a schedule with values between 0.0 and 1.0. The timestep value of the airflow is Maximum Airflow times the schedule value. Required if Airflow Is Scheduled = Yes. Unused if Airflow Is Scheduled = No. This schedule should have a ScheduleType with Numeric Type = Continuous and Range = 0.0 : 1.0.

Figure 29. Gap airflow configurations for airflow windows. (a) Air exhaust window: Airflow Source = InsideAir, Airflow Destination = OutsideAir; (b) Indoor air curtain window: Airflow Source = InsideAir, Airflow Destination = InsideAir; (c) Air supply window: Airflow Source = OutsideAir, Airflow Destination = InsideAir; (d) Outdoor air curtain window: Airflow Source = OutsideAir, Airflow Destination = OutsideAir; (e) Airflow to Return Air: Airflow Source = InsideAir, Airflow Destination = ReturnAir. Based on “Active facades,” Version no. 1, Belgian Building Research Institute, June 2002.

An IDF example: window with a constant airflow from inside to outside at 0.008 m³/s-m.

WindowProperty:StormWindow

This object allows you to assign a movable exterior glass layer (“storm window” or “storm glass”) that is usually applied to a window in the winter to reduce heat loss and removed in the summer. A WindowProperty:StormWindow object is required for each window that has an associated storm window. It is assumed that:

n When the storm glass is in place it is the outermost layer of the window, it covers only the glazed part of the window and not the frame, and it forms a tight seal. See Figure 30.

n When the storm glass is not in place it is completely removed and has no effect on window heat transfer.

Figure 30. Section through a single-glazed window without (left) and with (right) a storm glass layer. Not to scale.

With the addition of a storm window, single glazing effectively becomes double glazing, double glazing becomes triple glazing, etc.

The presence of a storm window is indicated by the report variable “Storm Window On/Off Flag” (see “Window Output Variables”). This flag is 0 if the storm window is off, 1 if it is on, and –1 if the window does not have an associated storm window.

The program automatically creates a window construction (ref: Construction) that consists of the storm window glass layer and its adjacent air layer added to the original (unshaded, or “bare”) window construction. In the eplusout.eio file this construction is called BARECONSTRUCTIONWITHSTORMWIN:n, where n is the number of the associated StormWin object. If the window has a shaded construction, the program creates a construction called SHADEDCONSTRUCTIONWITHSTORMWIN:n that consists of the storm window glass layer and its adjacent air layer added to the original shaded window construction.

The program also creates a WindowMaterial:Gas layer corresponding to the air layer adjacent to the storm glass. In the eplusout.eio file this layer is called AIR:STORMWIN:kMM, where k is the thickness of the air layer expressed as an integer number of millimeters.

Field: Window Name

This is the name of a window (or glass door) to which the storm glass is applied. Not all windows can accept WindowProperty:StormWindow. The rules are:

n The window must be an exterior window. WindowProperty:StormWindow is not applicable to interior (interzone) windows.

n The window construction (without the storm glass layer) can have up to three glass layers.

n If the window has an associated shaded construction (ref: WindowProperty:ShadingControl), that construction can have an interior shade or blind and up to three glass layers, or a between-glass shade or blind and two glass layers. The shaded construction cannot have an exterior shade or blind, cannot have a between-glass shade or blind and three glass layers, and cannot be switchable glazing.

n The window cannot be an airflow window, i.e., a window that has an associated WindowProperty:AirflowControl.

Field: Storm Glass Layer Name

This is the name of a window glass material. Storm windows are assumed to consist of a single layer of glass. A storm window frame, if present, is ignored.

Field: Distance Between Storm Glass Layer and Adjacent Glass

The separation between the storm glass and the rest of the window (Figure 30). It is measured from the inside of the storm glass layer to the outside of the adjacent glass layer.

Field: Month that Storm Glass Layer Is Put On

The number of the month (January = 1, February = 2, etc.) during which the storm window is put in place.

Field: Day of Month that Storm Glass Layer Is Put On

The day of the month that the storm window is put in place. It is assumed that the storm window is put in place at the beginning of this day, i.e., during the first simulation timestep of the day, and remains in place until that month and day given by the following two fields.

Field: Month that Storm Glass Layer Is Taken Off

The number of the month (January = 1, February = 2, etc.) during which the storm window is removed.

Field: Day of Month that Storm Glass Layer Is Taken Off

The day of the month that the storm window is removed. It is assumed that the storm window is removed at the beginning of this day, i.e., during the first simulation timestep of the day, and stays off until the month and day given by Month that Storm Glass Layer Is Put On, Day of Month that Storm Glass Layer Is Put On.

In the northern hemisphere, the month the storm window is put on is generally greater than the month it is taken off (for example put on in month 10, when it starts to get cold, and taken off in month 5, when it starts to warm up). In the southern hemisphere this is reversed: month on is less than month off.

An IDF example of WindowProperty:StormWindow. The storm window is put in place on October 15 and removed on May 1.

Importing Windows from WINDOW 5

WINDOW 6.3 is capable of writing IDF excerpts for Window data. This is the preferred method as no external file is necessary.

The WINDOW 5 program calculates the U-value, Solar Heat Gain Coefficient, solar transmission/absorption characteristics, visible transmission characteristics and other properties of a window under standard indoor and outdoor conditions. WINDOW 5 treats the whole window system—glazing, frame and divider. A sub-program of WINDOW 5 called THERM uses a 2-D finite element calculation to determine the effective conductance of frame, divider and edge-of-glass elements. Another sub-program, OPTICS 5, determines the solar-optical properties of glazing, including laminates and coated glass.

WINDOW 5 writes a data file containing a description of the window that was analyzed. An example is shown below. This file, which can be named by the user, can be read by EnergyPlus. For more complete description and examples, see the object description -- Construction:WindowDataFile.

In this way, the same window that was created in WINDOW 5 can be imported into EnergyPlus for annual energy analysis without having to re-input the window data. To obtain WINDOW 5 go to http://windows.lbl.gov. A major advantage of using WINDOW 5 to create window input for EnergyPlus is that you will have direct access to WINDOW 5’s expanding database of over 1000 different glass types; and you will be able to browse through this database according to different criteria (color, transmittance, solar heat gain coefficient, etc.) to help you select the best glass type for your application.

Although WINDOW 5 writes only one window entry on the WINDOW 5 data file, EnergyPlus users can combine two or more of these files to end up with a single WINDOW 5 data file with multiple window entries of different types. In this way a library of windows from WINDOW 5 can be built up if so desired. If you combine files like this you should be sure not to leave out or change any of lines from the original files.

3) import WINDOW 5 report containing layer-by-layer calculated values and overall glazing system angular values.

n The SHGC calculations in EnergyPlus for window layers input using full spectral data use a spectral weighting data set (derived from Optics5 data file ISO-9845GlobalNorm.std) that is different from the WINDOW 5 default spectral weighting data set (W5_NFRC_2003.std). This difference accounts for most of the variation in SHGC values reported by EnergyPlus and WINDOW 5 for full spectral data window layer input. This variation is more pronounced for window constructions of three glass layers or more.

n Users intending to select a window construction based on SHGC value for energy code compliance should base their selection on the value reported by WINDOW 5 since this is the officially recognized value.

The fixed version of the program will not show the above line; rather, there will be two lines such as shown below. If you have the above condition, with an editor you would break this into two lines:

In EnergyPlus, the Window5 data file is searched for each “Construction from Window5 Data File” object in the EnergyPlus input. This object has a very simple form:

If there is a window called ConstructionName on the Window5 data file, the data for that window is read from the file and the following EnergyPlus objects and their names are created. The “W5” prefixed to these names indicates that the object originated in the Window5 data file.

n WindowMaterial:Glazing for each of the glass layers. They will be named W5:ConstructionName:GLASS1,W5:ConstructionName:GLASS2 , etc.

n WindowMaterial:Gas or WindowMaterial:GasMixture for each of the gap layers. They will be named W5:ConstructionName:GAP1, W5:ConstructionName:GAP2 , etc.

n WindowProperty:FrameAndDivider (if the window on the Window5 data file has a frame and/or divider). It will be named W5:ConstructionName. This WindowProperty:FrameAndDivider will be assigned to any window on the input file that has a construction called “ConstructionName” even if that window has referenced another WindowProperty:FrameAndDivider (i.e., if WindowProperty:FrameAndDivider Name for that window is specified). In this case a warning will result.

EnergyPlus handles the “one glazing system” and “two glazing systems” cases differently. If there is one glazing system, the glazing system height and width from the Window5 data file are not used. Instead, the window dimensions are obtained from the window vertices that have been specified on the IDF file. However, a warning message will result if the height or width calculated from the window’s vertex inputs differs from the corresponding Window5 data file values by more than 10%. This warning is given since the effective frame and edge-of-glass conductances on the WINDOW 5 data file can depend on the window dimensions if the frame is non-uniform, i.e., consists of sections with different values of width, projection, or thermal properties.

If the WINDOW 5 data file entry has two glazing systems, System1 and System2, the following happens, as shown in the figure below. Assume that the original window is called WinOriginal. System1 is assigned to WinOriginal. Then EnergyPlus automatically creates a second window, called WinOriginal:2, and assigns System2 to it. The dimensions of WinOriginal are ignored; the dimensions of System1 on the data file are assigned to it, but the position of the lower left-hand vertex of WinOriginal is retained. The dimensions of System2 on the data file are assigned to WinOriginal:2. The lower left-hand vertex of WinOriginal:2 is determined from the mullion orientation and width.

Following is an example WINDOW 5 data file for a slider window with two identical double low-E glazing systems separated by a horizontal mullion. Each system has a frame and divider. Note that all dimensions, such as glazing height and width, are in millimeters; when EnergyPlus reads the file these are converted to meters. Following the data file example is a description of the contents of the file. That data used by EnergyPlus is shown in bold.

Window5 Data File for EnergyPlus

Window 5.0 v5.0.73

Date : Tue Nov 13 17:07:40 2001

Window name : DoubleLowE

Description : Horizontal Slider, AA

# Glazing Systems: 2

GLAZING SYSTEM DATA: Height Width nPanes Uval-center SC-center SHGC-center Tvis-center

System1 : 1032 669 2 1.660 0.538 0.467 0.696

System2 : 1033 669 2 1.660 0.538 0.467 0.696

FRAME/MULLION DATA: Width OutsideProj InsideProj Cond EdgeCondRatio SolAbs VisAbs Emiss Orient'n (mull)

L Sill : 97.3 25.4 25.4 500.000 1.467 0.500 0.500 0.90

R Sill : 97.3 25.4 25.4 500.000 1.467 0.500 0.500 0.90

L Head : 70.2 25.4 25.4 18.822 1.490 0.500 0.500 0.90

R Head : 70.2 25.4 25.4 18.822 1.490 0.500 0.500 0.90

Top L Jamb : 54.3 25.4 25.4 31.141 1.503 0.500 0.500 0.90

Bot L Jamb : 54.3 25.4 25.4 500.000 1.494 0.500 0.500 0.90

Top R Jamb : 70.2 25.4 25.4 500.000 1.518 0.500 0.500 0.90

Bot R Jamb : 97.6 25.4 25.4 264.673 1.547 0.500 0.500 0.90

Mullion : 53.5 25.4 25.4 500.000 1.361 0.500 0.500 0.90 Horizontal

Average frame: 75.5 25.4 25.4 326.149 1.464 0.500 0.500 0.90

DIVIDER DATA : Width OutsideProj InsideProj Cond EdgeCondRatio SolAbs VisAbs Emiss Type #Hor #Vert

System1 : 25.4 25.4 25.4 3.068 1.191 0.500 0.500 0.900 DividedLite 2 3

System2 : 25.4 25.4 25.4 3.068 1.191 0.500 0.500 0.900 DividedLite 2 3

GLASS DATA : Layer# Thickness Cond Tsol Rfsol Rbsol Tvis Rfvis Rbvis Tir EmissF EmissB SpectralDataFile

System1 : 1 3.00 0.900 0.50 0.33 0.39 0.78 0.16 0.13 0.00 0.16 0.13 CMFTIR_3.AFG

2 6.00 0.900 0.77 0.07 0.07 0.88 0.08 0.08 0.00 0.84 0.84 CLEAR_6.DAT

System2 : 1 3.00 0.900 0.50 0.33 0.39 0.78 0.16 0.13 0.00 0.16 0.13 CMFTIR_3.AFG

2 6.00 0.900 0.77 0.07 0.07 0.88 0.08 0.08 0.00 0.84 0.84 CLEAR_6.DAT

GAP DATA : Gap# Thick nGasses

System1 : 1 12.70 1

System2 : 1 12.70 1

GAS DATA : GasName Fraction MolWeight ACond BCond CCond AVisc BVisc CVisc ASpHeat BSpHeat CSpHeat

System1 Gap1 : Air 1.0000 28.97 0.002873 7.76e-5 0.0 3.723e-6 4.94e-8 0.0 1002.737 0.012324 0.0

System2 Gap1 : Air 1.0000 28.97 0.002873 7.76e-5 0.0 3.723e-6 4.94e-8 0.0 1002.737 0.012324 0.0

GLAZING SYSTEM OPTICAL DATA

Angle 0 10 20 30 40 50 60 70 80 90 Hemis

System1

Tsol 0.408 0.410 0.404 0.395 0.383 0.362 0.316 0.230 0.106 0.000 0.338

Abs1 0.177 0.180 0.188 0.193 0.195 0.201 0.218 0.239 0.210 0.001 0.201

Abs2 0.060 0.060 0.061 0.061 0.063 0.063 0.061 0.053 0.038 0.000 0.059

Rfsol 0.355 0.350 0.348 0.350 0.359 0.374 0.405 0.478 0.646 0.999 0.392

Rbsol 0.289 0.285 0.283 0.282 0.285 0.296 0.328 0.411 0.594 1.000 0.322

Tvis 0.696 0.700 0.690 0.677 0.660 0.625 0.548 0.399 0.187 0.000 0.581

Rfvis 0.207 0.201 0.198 0.201 0.212 0.234 0.278 0.374 0.582 0.999 0.260

Rbvis 0.180 0.174 0.173 0.176 0.189 0.215 0.271 0.401 0.648 1.000 0.251

System2