Fibrous glass duct liner insulations are manufactured from glass fibers bonded with thermosetting resin. They are dimensionally stable, withstand abuse, and provide a cleanable, fire-resistant interior surface designed to minimize friction loss. This interior treatment may be in the form of a coating and/or a mat facing. Two forms are available. Both are designed to meet physical property requirements of ASTM C 1071, Standard Specification for Duct Lining Insulation (Thermal and Sound Absorbing Material):