Scope: This test applicable to both residential and commercial fenestration products.

Applicable Products: Windows, Doors, Skylights, Curtain Walls

Test Procedure: This procedure utilizes computer simulation software to determine overall product thermal transmittance (U-Factor), including frame and glass elements. Two-dimensional finite element software is used to calculate the U-Factors of individual elements of the window. Frame, Edge and Center-of-Glass (COG) U-Factors are calculated using the WINDOW and THERM software programs developed by Lawrence Berkeley National Laboratory (LBNL).

The ANSI/NFRC 100 procedure calculates U-Factors for winter conditions of 70ºF (21ºC) interior temperature and 0ºF (-18ºC) exterior temperature.

End Result: The U-Factor of the product is determined. The U-Factor can be used to determine energy losses through products. This computer simulation is used in conjunction with the NFRC 102 test method to prove the validity of the results for the product. This typically is used to certify windows, doors, skylights and curtain walls for U-Factor and to qualify for Energy Star.

Special Notes: Alternative U-Factor methods which may be appropriate are NFRC 102, AAMA 1503, CSA A440.2, ASTM C1199, and ASTM C1363.


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