1.1 This practice specifies standard test specimen sizes and test conditions, as well as the calculation and presentation of the thermal transmittance and conductance data measured in accordance with Test Method C1199. The standard sizes and conditions are to be used for fenestration product comparison purposes. The specifier may choose other sizes and conditions for product development or research purposes. 1.2 This practice refers to the thermal transmittance, , thermal conductance, , and the corresponding thermal resistances, u and Rc , respectively, of a fenestration system installed vertically in the absence of solar and air leakage effects. Note 1-To determine air leakage effects for windows and doors, Test Methods E283 and E1424 should be referenced. For solar effects, ANSI/ASHRAE Standard 74-1988 should be referenced. 1.3 A discussion of the definitions and underlying assumptions for determining the thermal transmittance and thermal conductance is included. 1.4 This practice specifies the procedure for determining the standardized thermal transmittance using the experimentally determined thermal conductance, , and specified values of the room-side and weather-side surface conductances, I and hII , respectively. 1.5 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.