rFOIL 4320 Standard Concrete Underpad is an outstanding reflective insulation and puncture-resistant vapor barrier. It consists of a double layer of polyethylene bubbles sandwiched between an aluminum surface and a clear polyethylene sheet. It is ideal for many under-slab insulation applications because a protective film is applied to the aluminum surface virtually eliminating the risk of corrosion. Using rFOIL 4320 Standard Concrete Underpad in your construction project can improve the efficiency of radiant heating systems, significantly decrease heat loss to the ground below and redirect radiant heat energy back to living area when properly installed with the clear side facing upwards. It extends the life of heating systems and generates faster reaction time for radiant floor heating It provides exceptional thermal value and a strong, permanent vapor and radon barrier and acts as a cost-effective alternative to rigid foam insulation.