RECOMMENDED USESTapered ACFoam Composite/GB consists of Atlas closed-cell polyiso foam bonded to 1/4" primed glass-mat gypsum board on the top with a fiber-reinforced felt facer on the bottom. It is manufactured in a tapered profile to attain positive drainage.  The glass-mat gypsum board provides a dense protection layer for the primary foam insulation and has a 500 psi compressive strength, which makes Composite/GB a good choice where foot traffice is a concern.