On sub-ambient temperature systems, humid ambient conditions cause a vapor driving force toward the insulation which, if not retarded, is detrimental to the insulation's thermal resistance. Therefore a vapor retarder should resist degradation. Degradation in this test method is induced by elevated temperature and humidity conditions.

1.1 This test method covers the determination of the aging resistance of flexible low permeance vapor retarders for thermal insulation as classified in Specification C 1136. Water vapor permeance measurement and visual inspection after exposure at elevated temperature and humidity are used to assess vapor retarder response.

1.2 Typical vapor retarders applicable to this test method that are intended for indoor use include foil-scrim-kraft laminates, metallized polyester-scrim-kraft laminates, treated fabrics, treated papers, films, foils, or combinations of these materials that may comprise a vapor retarder material. This test method is not intended for assessment of the liquid-applied coatings, sealants, or mastics commonly used with insulation products.

1.3 The values stated in inch-pound units are to be regarded as standard. The SI units given in parentheses are for information purposes only.

1.4 This standard does not purport to address all of the safety concerns, 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.