Insulate your floor or wall space with EcoFoil Between Joist Insulation. Adding this quick and clean insulation will add comfort and energy efficiency to your home. EcoFoil radiant barrier insulation uses double layers of polyethylene bubbles sandwiched between highly reflective layers of aluminum, providing a radiant heat block. EcoFoil blocks 96% of radiant heat giving you a new level of comfort. EcoFoil joist insulation comes in two sizes (16" and 24" widths) to make installation easy. Each side has a 3/4" staple strip to hold it securely in place.