Fi-Foil's RBI Shield™ Double Bubble Reflective Insulation keeps floors warmer in the winter and cooler in the summer while also increasing comfort. Due to its high thermal reflectivity, RBI Shield™ is the best insulation product for floors, especially floors that incorporate radiant floor heating. In addition to its superior insulating qualities, it is the best vapor retarder on the market and has properties that will inhibit radon gas.