In terms of HVAC Ductworks functionality, Insulation facing is often used to limit vapor drive with the ultimate goal of preventing condensation.
Perm rating is a standard measure of the water vapor permeability of a material. The higher the number, the more readily water vapor can diffuse through the material. A perm rating of less than 0.1 is considered a Class I impermeable vapor retarder, which is also considered a vapor barrier.
Foil scrim kraft (FSK)
Poly scrim kraft (PSK)
All service jacket (ASJ)
All of above insulation facing Perm rating less than 0.1 that meet the Class I impermeable vapor retarder. So the Insulation facing suitable for a wide variety of applications, it can be used as vapor barrier layer for insulation materials, with good aging resistance and corrosion resistance.