This specification covers the classification, composition, and physical properties of flexible fibrous glass insulation for use as interior surface of walls and roofs of metal buildings. The basic insulation blanket is designed to be postprocessed by a laminating process that applies an adhesive bonded facing to provide the interior finish and vapor retarder requirements for the building envelope The flexible insulation is furnished into Types I and II. Type I which is a glass processed from the molten state into fibrous form, bonded with a thermosetting resin, and formed into a resilient flexible blanket or batt. Type II is a Type I material supplied with a suitable facing adhered to one surface. The following physical properties of Types I and II materials shall be determined: thermal resistance, surface burning characteristics, combustion characteristics, water vapor sorption, fungi resistance, corrosiveness, odor emission, dimensional tolerances, and humid aging.