Insulperm^® is a patented, CFC-free, expanded polystyrene insulation board of nomimal 1 pcf density. It’s specifically designed for use in Siplast Lightweight Insulating Concrete applications. When used in a stair-stepped configuration, it serves as the base for the system’s slope-to-drain capability. This lightweight board is specifically designed to give the system good composite strength while allowing the release of moisture vapor. Insulperm® is supplied in 2 ft. x 4 ft. boards with thickness ranging from 1 in. to 28 in.