CeraZorb is a synthetic cork underlayment that is installed on top of a subfloor and below a heating element. It is recommended when installing an electric floor heating system over a concrete slab to prevent heat loss. By creating a thermal break, the heat is prevented from sinking into the concrete, and more heat radiates into the floor covering and room. In addition to preventing unnecessary heat loss, CeraZorb provides sound dampening benefits and double the crack isolation benefits when compared to cork. This pack of four 2' x 4' sheets offers up to 32 sq. ft. of coverage and works well for smaller projects or as a supplemental add-on for a larger pack of CeraZorb.