Scope: This test is applicable to large assemblies, such as walls and roofs.

Applicable Products: Any exterior wall or roof assembly, including steel stud wall systems, insulated concrete forms, tilt-up concrete walls, and insulated metal panels

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 C1363 test, the assembly is placed in a wall between the warm and cold rooms. Temperatures 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 assembly is measured to determine the U-Factor and/or R-Value of the assembly.

End Result: The thermal transmittance (U-Factor) and/or thermal resistance (R-Value) of the assembly is determined. These can be used to determine energy losses through assemblies and the impact on overall building energy usage.

Special Notes: This method is used to determine R-Value for complex systems, when simple material tests such as ASTM C518 and C177 are not applicable.


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