RECOMMENDED USESTapered ACFoam Composite/PB consists of Atlas closed-cell polyiso bonded to 1⁄2" perlite on the top and a fiberreinforced felt facer on the bottom. It is manufactured in a tapered profile to attain positive drainage. The perlite top eliminates the need for cover boards or vented base sheets normally recommended over foam insulations. Tapered ACFoam Composite/PB may be used with BUR, modified bitumen, and certain single-ply systems. Available in 4´ x 4´ (1220mm x 1220mm) only.