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Stylized Text: Software for Fenestration.

Picture of Fenestration Logo. Computer programs useful for designing buildings, windows, and shading systems are available from a variety of sources.

FSEC's more general Energy Gauge® software, for building energy performance assessment, is available at

Some fenestration-related software is available for free download from this site. Click on the appropriate link below.

FSEC Software  |  Other Fenestration Software Sources

FSEC Software

The following computer programs are being developed for use in building energy analyses, including window and shade design and performance evaluation. They are offered here for free download. The programs come with no warranty, guarantee, or other legal protection. We believe them to be based upon correct formulations and proper programming, but the user must bear full responsibility for the consequences of their use.

The program descriptions follow the link to the program and the instructions for downloading. The new versions will be posted for download as they become available. Please check back monthly, to see which ones have been added.


  1. In most cases, the program is an exe file ready to run. Download it into the directory recommended above below the download link. Also download any associated files and subdirectories to the recommended directory. For example, INFILES and OUTFILES folders. If these are present, the contents of the INFILES folder are needed by the program, and program print results go to the OUTFILES folder by default. See 4 below to create a link on your desktop to run the program.
  2. If the file you have selected has a “.zip” extension, you must obtain an unzipping program, such as WinZip to “unarchive” this file. (If this is the case, the program is provided as a zipped file to reduce download time.) In the future we plan to offer zipped and unzipped versions and eventually convert all files and folders into a self-extracting exe file you can download and then run to install the program. This is already the case with SUNPATH 3.2
    You can obtain a free trial version of WinZip from ( In this case you tell your web browser to save the program you want into a download folder or other directory of your choosing. Remember where you saved the zip file.
    Exit your web browser and run WinZip program, telling it to unzip the file you have downloaded. If prompted for where to put the extracted (unzipped) files, it is recommended that you direct WinZip to the folder recommended for the program. The extraction process may result in a setup.exe file to run. If there is a Setup Procedure, such as with SunPath, execute the setup.exe and follow instructions to install the program in a folder under Program Files named Florida Solar Energy Center and in a subfolder whose name is recommended above.
  3. Once you have saved an exe file, you can run it as follows. Click on Start and Run and use the “Browse” button to run the exe file you have downloaded. Then install the program in a folder named “Florida Solar Energy Center” in your Program Files folder.
  4. If the installation process leaves an icon for the program you have installed on your desktop, or puts one in your Start button Programs list, then you can execute (run) the program from this icon. If it does not, you can create one yourself as follows.
    Right click on your desktop away from any icon. In the pull down window select New>Shortcut. Then click on the Browse button and use the drive and file list window to point to the program’s “.exe” file. For SUNPATH, this file is called sunpath.exe and should have an icon next to it with “SP” on it. Click on this file, click on OK, edit the name to appear under the icon to “SUNPATH” or “SUNPATH32,” and click on Finish. The icon should appear on your desktop. You can then copy this shortcut into your Start > Programs list if you like. Double clicking on the desktop icon will start the program. Single clicking on the icon in the Start>Programs list will run it.


Click here to download
Self-extracting installation file.
Save setup.exe in
c:\Program Files\Florida Solar Energy Center\SunPath,
then run it

This is a fully MS Windows-based implementation of the popular SUNPATH 2.0, an MS DOS application. It allows the user to select latitude and longitude coordinates for a site of interest (from a many-city library provided or by hand entry) and then determine the position(s) in the sky of the center of the sun for any day of the year and time of day, or for a sequence of days and times. The results are output into an ASCII file with columns labeled and conditions specified, easy to import into any word processing program, spreadsheet, or for direct printing. Also included is a simple procedure for plotting multicolor sunpath diagrams. These charts show the altitude angle (above the horizon) variation and the azimuth angle (degrees of rotation from north toward east) variation of the sun from sunrise to sunset for selected dates in each of the 12 months of the year. The new version is very user-friendly and a minimum of reading is needed to run the program the first time.


Click here to download

Directly executable file. Install the exe files and all the other files in the Awnshade directory shown below. Run awnshade.exe to run the program. Recommend install in
c:\Program Files\Florida Solar Energy Center\AWNSHADE\

This is an old MS-DOS program written in Visual Basic for DOS. It does offer a crude form of windows and graphics, and is still available for download. The user selects which type of window shading is of interest from a menu of the following choices: 1. Awning only. Horizontal overhang above window, or lower front edge of awning, with and without side walls extending from lower edge back to the wall on either side of the window. 2. Vertical side fins. Rectangular vertical planar shades to either side of the window and perpendicular to the wall. 3. Awning plus side fins. A combination of cases 1 and 2. The user then enters a solar altitude angle and a relative azimuth angle (0 degrees being perpendicular to the wall) and the program calculates the unshaded fraction of the window area, that fraction of the total window area which receives direct sunlight without being shaded. The user also has the option of determining the effective unshaded fraction for uniformly diffuse incident radiation and to output a table of unshaded fractions for a range of solar altitude and relative azimuth angles.


Click here to download

Directly executable file. Install the exe file and the other files in the AWNSHADE3 directory as indicated below.
Run awnshade3.exe to run the program. Recommend install in
c:\Program Files\Florida Solar Energy Center\AWNSHADE\

BETA Review Version only.

Use at your own risk.

This is a fully MS Windows-based implementation of AWNSHADE 1.0, described above, to be released Summer 2004. To install, copy all files, including AWNSHADE3.EXE, from the link "Click here to download" above.

The default (and recommended) installation subdirectory on your computer is
c:\Program Files\Florida Solar Energy Center\AWNSHADE\

Put the files in the above directory.


The files Awnshade1.ico and Awnshade2.ico are provided to use as the shortcut icons for AWNSHADE3.exe, especially USEFUL if you place a shortcut on your desktop. Once you have a shortcut on your desktop, right click on it and then click on "Change Icon" and "Browse" to one of these two icon files. Read the README.TXT file for further installation and operating instructions.

You should create an "OUTFILES\" directory or folder in the program's folder. Data files created by the program will be placed in this folder by default. The program gives you the option of choosing another directory to store the output data files in another folder on your computer. Simply follow directions while running the program.



Dr. Christian Gueymard developed the SMARTS terrestrial solar spectral irradiance calculation model while working at the Florida Solar Energy Center in the 1990s. (The acronym stands for a Simple Model of the Atmospheric Radiative Transfer of Sunshine.) For more information about solar radiation databases and computational products in general, you can visit NREL's

Solar Radiation Resource Information web page at:

SMARTS computes clear sky spectral irradiances (direct beam, circumsolar, hemispherical diffuse and total on a prescribed receiver plane - tilted or horizontal) for one set of atmospheric conditions (user specified, or selected from 10 standard atmospheres); and for one to many points in time or solar geometries. The algorithms were developed to match the output from the MODTRAN complex band models within 2%. The algorithms are implemented in compiled FORTRAN code for the Macintosh and PC platforms. Source code is available. The algorithms are used in conjunction with files for atmospheric absorption of atmospheric components and spectral albedo functions. The spectral resolution is 0.5 nm from 280 nm to 400 nm; 1 nm from 400 nm to 1750 nm, and 10 nm from 1750 nm to 4000 nm. The user constructs a text file of between 20 and 30 lines of simple text and numbers specifying input conditions and up to 28 spectral output parameters. The user may specify field of view angles for direct beam computations, and a separate computation for the circumsolar component. Gaussian or triangular smoothing functions with user-defined bandwidth may be specified to compare model results with measurements made with the specified pass band. The user may specify only Ultraviolet (280 nm - 400 nm) computations for erythemal dose, UV index, etc. Photometric (luminous flux) computations, weighted by a selected photopic response curve, may also be specified. Output is spreadsheet-compatible ASCII text files and header information with prescribed conditions.

We previously offered a DOS-based user interface to the SMARTS model called SUNSPEC 1.0 for free download from this web site.  In recent years, the model has been greatly improved and expanded by Dr. Gueymard, working with the National Renewable Energy Laboratory in Golden, Colorado.  The FORTRAN computer coding of the SMARTS program has been available to researchers for some time, but it requires a certain amount of knowledge of atmospheric physics to operate properly.

Thanks to various sponsorships, the new SMARTS-2 model is now available for Windows, Macintosh, and Linux operating systems.  Graphic user interface versions for Windows are also available, making it easier to use. 

A comprehensive description of the SMARTS model can be found in FSEC publication # FSEC-PF-270-95 dated December 1995 or from NREL at

SMARTS version 2.9.2 is the model used to generate the American Society for Testing and Materials (ASTM) terrestrial
reference spectra for ASTM Standard G-173-03 "Standard Tables for Reference Solar Spectral Irradiance at Air Mass 1.5: Direct Normal and Hemispherical for a 37 Tilted Surface".

To get the latest software for SMARTS

SMARTS version 2.9.5 for Windows, Macintosh and Linux operating systems was made available for download by NREL in 2006. To obtain the current version, visit


OptPropConvert 1.0 Beta
Click here to download

This is an executable file. Save it to the directory shown below.
Run OptPropconvert.exe to run the program.
Recommend install in
c:\Program Files\Flo
rida Solar Energy Center\OptPropConvert

This is a small Windows utility program which can be used to read spectral optical property data files published by the National Fenestration Rating Council (, output as text files from the Optics 5 program’s glazing library. The program then converts the spectral transmittance and reflectance data into solar- and photopic- weighted average values for the refractive index and material internal absorptivity. These quantities are needed to run the program TDDTrans.exe described below, and may be useful for other purposes as well.

Caution: This is a draft beta version only, not to be used for official rating purposes until the NFRC has accepted it for use in rating TDDs.


TDDTrans 1.0 Beta
Click here to download

This is an executable file. Save it in the directory shown below.
Run TDDTrans.exe to run the program.
Recommend install in
c:\Program Files\Florida Solar Energy Center\TDDTrans

This Windows based computer program was developed on contract to the National Fenestration Rating Council in order to perform the calculations specified by a draft standard practice for the rating of Tubular Daylighting Devices (TDDs)— also known as tubular skylights—for solar heat gain and visible transmittance properties. It was upgraded with U.S. Department of Energy funding to better enable calculations with spectrally selective optical components.

Caution: This is a draft beta version only, not to be used for official rating purposes until the NFRC has adopted an official standard practice for the rating of these devices for solar gain and visible transmittance, and until this beta version has been converted to accurately follow the procedures spelled out in the official standard.

Other Fenestration Software Sources

RESFEN is a program for calculating the annual heating and cooling energy use and costs due to fenestration systems in residential buildings. RESFEN (RESidential FENestration) also calculates their contribution to peak heating and cooling loads.  This program was developed by and is available from Lawrence Berkeley National Laboratory.

Other Software Tools Available from LBNL: For a list of related software developed at Lawrence Berkeley National Laboratory, some of which are downloadable, click on this link and then click on "Software". In particular, WINDOW is the cornerstone of LBNL's fenestration software series. It calculates total window U-factors, SHGC, visible transmittance, and other related properties. Optics is a preprocessor for WINDOW's glass database. THERM models two-dimensional heat-transfer effects in building components such as windows, walls, foundations, roofs, and doors; appliances; and other products where thermal bridges are of concern. The software program FRAME, developed in Canada, performs similar heat transfer calculations.

Software from the National Research Council of Canada: SkyVision is a program to size and evaluate skylights. DaySim is a daylighting analysis software that calculates the annual daylight availability in arbitrary buildings as well as the lighting energy use of automated lighting controls (occupancy sensors, photocells) compared to standard on/off switches. The program combines the backward raytracing software Radiance, developed by Greg Ward at the Lawrence Berkeley National Laboratory, with a daylight coefficients approach. The underlying sky model to calculate annual illuminance profiles is the Perez all weather sky model. A stochastic model from Skartveit and Olseth has been adapted to calculate the short-time-step development (down to 1 minute) of indoor illuminances based on hourly mean direct and diffuse irradiance values.

DAYSIM was developed at the Lighting Group of the National Research Council Canada and at the Solar Building Design Group of the Fraunhofer Institute for Solar Energy Systems. LightSwitch Wizard is the daylighting analysis tool underlying DaySim. It has been developed to support daylighting-related design decisions in commercial buildings during an early design stage. The tool offers a comparative, reliable, and fast analysis of the amount of daylight available in single offices and classrooms as well as the lighting energy performance of automated lighting controls (occupancy sensors, photocells) compared to standard on/off switches.

RayDirect, Daylight redirecting software

Lesodial, Daylighting software

ADELINE provides architects and engineers with accurate information about behavior and the performance of indoor lighting systems. Both natural and electrical lighting problems can be solved, in simple rooms or the most complex spaces. The program is an integrated lighting design computer tool developed by an international research team within the framework of the International Energy Agency (IEA) Solar Heating and Cooling Programme Task 12. The computer program is supported by the Fraunhofer Institute for Building Physics.

Lumen Designer is a Computer Aided Design (CAD) system for designing architectural spaces and illuminating them with both electric lighting and daylighting. The software includes extendable libraries of objects, materials, and lighting products, and radiosity calculations permitting full color rendering of the illuminated space in 3D perspective. It is the latest embodiment of LumenMicro.

Radiance and Desktop Radiance is a highly accurate ray-tracing software system for UNIX computers that is licensed at no cost to users for non-commercial use; commercial use licenses including distribution rights are available for a fee. Radiance was written initially by Greg Ward at Lawrence Berkeley National Laboratory and further developed with primary support from the U.S. Department Of Energy and additional support from the Swiss Federal Government. It is copyrighted by the Regents of the University of California.

Solar Position and Solar Spectrum Software

Solar Position Software. We think the best is our own SUNPATH v. 3.2, but there are other sources on the web. Do a search on "sun position" or "sun paths".

Solar Spectrum Software. We think the best is a model developed originally by Dr. Christian Gueymard when he worked at FSEC a number of years ago. In the intervening years Dr. Gueymard has improved and advanced his model, the SMARTS model, and it is now available through the National Renewable Energy Laboratory in Golden, CO. You can download the SMARTS model for free from their web site.