Standard: ASTM C1199 – Standard Test Method for Measuring the Steady-State Thermal Transmittance of Fenestration Systems Using Hot Box Methods

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

Applicable Products: Windows, Doors, Skylights, Curtain Walls

Test Procedure: The test utilizes an apparatus known as a guarded hot box. The guarded hot box consists of a cold room and a warm room.  The cold room contains refrigeration coils to maintain temperatures as low as -22ºF (-30ºC) and fans to replicate wind speeds of 15 mph (24 kph). The warm room contains electric heating elements to maintain temperatures up to 100ºF (38ºC). The warm room is enclosed within a second room, known as the guard room, with the same heating capabilities.

In the ASTM C1199 test, the product is placed in a wall between the warm and cold rooms. Temperatures of 70ºF (21ºC) and º0F (-18ºC) and a wind speed of 15 mph (24 kph) are maintained in the two rooms until steady-state conditions have been met for temperature on both sides and energy input to the warm side. The heat flow through the product is measured to determine the U-Factor of the product.

End Result: The thermal transmittance (U-Factor) of the product is determined. The U-Factor can be used to determine energy losses through products. This method is the underlying test method for the NFRC 102 test.

Special Notes: Alternative U-Factor methods which may be appropriate are NFRC 100, NFRC 102, AAMA 1503, CSA A440.2, and ASTM C1363.


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