1. Scope 1.1 This test method provides requirements and guidelines and specifies calibration procedures required for the measurement of the steady state thermal transmittance of fenestration systems installed vertically. This test method specifies the necessary measurements to be made using measurement systems conforming to either Test Method C236 or C976 for determination of fenestration system thermal transmittance. 1.2 This test method refers to the thermal transmittance, , thermal conductance, , and the corresponding thermal resistance, Ru and c, respectively, of a fenestration system installed vertically in the absence of solar and air leakage effects. Note 1-Although this test method is a separate document from Test Methods C236 and C976, it is anticipated that it will be integrated into these documents when they are revised. The methods described in this document may also be adapted for use in determining the thermal transmittance of sections of building wall, roof and floor assemblies containing thermal anomalies which are smaller than the hot box metering area. 1.3 A discussion of the terminology and underlying assumptions for measuring the thermal transmittance is included. 1.4 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.