WarmlyYours 2' x 4' CeraZorb Insulating Synthetic Cork Underlayment Sheet, Lightweight, 4 Pack, 32 sq. ft. Coverage SYNTHETIC CORK UNDERLAYMENT: Specifically designed for setting tile and stone and is an excellent insulation choice under our WarmlyYours TempZone Electric Radiant Floor Heating product. R-value 1.5, with compressive strength 34 psi at 10% deformation, IIC 52 wood construction, FIIC 59 - 7.5" concrete slab. IIC 20 - 6" concrete slab, TCNA Robinson test Light Commercial PREVENT HEAT LOSS: Recommended when installing an electric floor heating system over a concrete slab. By creating a thermal break, the heat is prevented from sinking into the concrete, and more heat radiates into the floor covering and room LIGHTWEIGHT AND SOUND DAMPENING: Up to 25 times lighter than traditional 1/4" backer board, also provides sound dampening benefits and double the crack isolation benefits when compared to cork COMPATIBLE SIZE: Available in 2 x 4 and 4 x 4 sheets, 5 mm. (roughly 3/16 in.) thick. This is a pack of 4 sheets, provides 32 sq. ft. of coverage and is great for medium to large projects 5-YEAR WARRANTY: Limited 5-year warranty and 24/7 lifetime installation and technical support at 800-875-5285