THERM Documentation

THERM Documentation

User Manuals

The THERM 7 User's Manual is in the process of being updated (from the THERM 2 version), and as sections of the manual are updated, they will be available here. Below are links to sections (PDF files) that are complete to date:

National Fenestration Rating Council WINDOW / THERM Simulation Manual

Comparison of WINDOW 5 / THERM 5 and WINDOW 6 / THERM 6 Results for Specular Glazing Systems (PDF)


The THERM Notes section contains information that is not yet in a User Manual.

Sample Files

  • Sample DXF and THERM files (Example THERM and DXF -- some of these are referenced in the THERM 7 User Manual Drawing Tips excerpt above. The files include:
    • auto.dxf
    • autofill.dxf
    • autofill2.dxf
    • cen1.dxf
    • cen2.dxf
    • circles.dxf
    • lowhoriz.dxf
    • bad1.THM
    • bad2.THM
    • bad4.THM
    • cut&paste.THEm
    • Spacer-half.thm
  • ​Aluminum Slider Example Files (ZIP)
    • These sample files are from the NFRC THERM 5.2 / WINDOW 5.2 Simulation Manual. There may be a few slight difference between the files and those shown in the manual (for example the spacer in the aluminum slider example). When running them in later versions of THERM, make sure to regenerate boundary conditions, and when using them in later versions of WINDOW, make sure to recalculate all the results.


  • Creating THERM Sample File (Flash Video)
    Specification document to accompany the Tutorial (PDF)
  • Creating a Steel Stud Wall in THERM (Flash Video)
    • Windows Media Player (WMV)
    • QuickTime (MOV)
  • U-factor tags explanation (Flash Video)
    • Windows Media Player (WMV)
    • QuickTime (MOV)
  • DXF Underlay — False Die Mold Method (Flash Video)
  • The Calc Manager in THERM has been made into a multi-threaded process which allows it to take advantage of multi-core processors
    • QuickTime (MOV)
  • Displaying Surface Condensation Potential in THERM 7
    • QuickTime (MOV)
  • Viewing R-values Instead of U-factors in THERM 7
    • QuickTime (MOV)
  • Using the Updater Function to Download a New Version
    • QuickTime (MOV)

Technical Documentation

Algorithm Documentation

WINDOW7 and THERM7 implement the ISO 15099 algorithms:

  • ISO 15099
    • The algorithms in WINDOW6 and THERM6 follow the procedures presented in ISO 15099:
    • "Thermal performance of windows, doors and shading devices - Detailed calculations."
    • See: ANSI Standards Store: ISO 15099:2003

In addition to implementing ISO 15099 algorithms in WINDOW7 and THERM7, we have added additional capabilities to WINDOW7.

The following reports and papers describe these additional capabilities and/or elaborate on ISO15099.

  • Deflection in Glazing Systems:
    • Thermal Performance of Deflected IGU (PDF)
    • July 16, 2012
  • Thermal Algorithm Documentation for THERM:
    • Conrad 5 & Viewer 5 Technical and Programming Documentation (PDF)
    • June 20, 2006
  • Thermal Algorithm Documentation for WINDOW:
    • TARCOG: Mathematical Models for Calculation of Thermal Performance of Glazing Systems with or without Shading Devices (PDF)
    • October 17, 2006
    • (Draft, still under review and revision)
  • Venetian Blind Algorithm Documentation:
    • Calculation of Optical Properties for a Venetian Blind Type of Shading Device (PDF)
    • October 20, 2006
    • (Draft, still under review and revision)
  • Woven Shade Algorithm Documentation:
    • Implementation of Woven Shade Method in Layeroptics.DLL (PDF)
    • November 9, 2006
    • (Draft, still under review and revision)
  • Bidirectional Optical Properties of Slat Shading: Comparison Between Raytracing and Radiosity Methods (PDF)
    • (Submitted to Solar Energy but not yet published)
  • Documentation for LBNL BSDF XML format:
    • Found in Section 6.4 of the WINDOW 6.1 / THERM 6.1 Research Version User Manual (PDF)
  • WINDOW BTDF Output File Documentation
    • Found in Section 6.3 of the WINDOW 6.1 / THERM 6.1 Research Version User Manual (PDF)
  • Verification Results
    • WINDOW 6 Verification Results (PDF)
    • June 12, 2006
    • (Draft, still under review and revision)
  • Joe Klems Matrix Method publications
    • A New Method for Predicting the Solar Heat Gain of Complex Fenestration Systems. I. Overview and Derivation of the Matrix Layer Calculation 1993 (PDF)
    • A New Method for Predicting the Solar Heat Gain of Complex Fenestration Systems. II. Detailed Description of the Matrix Layer Calculation 1993 (PDF)
  • Frit Model Documentation
    • Optical Model of Fritted Glazing in WINDOW, 9/24/2012​ (PDF)

THERM 2 User's Manual

The THERM 6.3 User's Manual has not been completed yet, so in the meantime, the following documents will cover most of the features of the program.

  • Entire Manual in PDF Format (PDF)

Other Useful Information

  • THERM 2.1 (including 2.1a) New Features Documentation (PDF)
  • THERM Drawing Tips (PDF)
    (This is Chapter 10 from an older THERM manual, which has some valuable drawing information that is not yet in any other manual. It references files in a CD that are unfortunately no longer available)
  • Teaching Students About Two-Dimensional Heat Transfer Effects in Buildings, Building Components, Equipment, and Appliances Using THERM 2.0 (PDF)
    Published in ASHRAE Transactions 1999, Vol 105, Part 1.