Flat Roof Insulation provides high long-term R-Values and saves labor installation time. Suitable for use with all roofing membrane materials, expanded polystyrene (EPS) roof insulation is compatible with loose-laid and attached single-ply membranes, conventional built-up roofing or modified bitumen systems. Flat Roof Insulation is unfaced EPS and is suitable for use with loosely laid single-ply membranes. Flat EPS Roof Insulation is also used with conventional BUR and mechanically or adhesively attached single-ply and modified bitumen membranes when field-applied cover boards are used.