ASTM C1258-21a PDF Download

ASTM C1258-21a is a standard test method that determines the resistance of flexible low permeance vapor retarders for thermal insulation to elevated temperature and humidity. The test method involves measuring the water vapor permeance of the vapor retarders and conducting visual inspections after exposure to elevated temperature and humidity.

The scope of this test method specifies that it applies to vapor retarders classified in Specification C1136. These vapor retarders are typically used for indoor applications and may include materials such as foil-scrim-kraft laminates, metallized polyester-scrim-kraft laminates, treated fabrics, treated papers, films, foils, or combinations thereof. However, it is important to note that this test method is not intended for assessing liquid-applied coatings, sealants, or mastics commonly used with insulation products.