5mm (1/4 inch) closed cell polyethylene foam sandwiched between WATERPROOF METALIZED REFLECTIVE FILM on both sides.Heating and cooling costs are about 60% of the average American Household energy bill. The most effective way to cut these cost is to lower the amount of heat transferred into the home in the summer an out of the home in the winter. Our Radiant Barrier/Reflective Insulation is made from double-sided 99% aluminum foil, with closed-cell polyethylene foam. It provides optimal protection by reflecting up to 97% of radiant energy, in addition to resisting conductive and convective heat transfers. Additional Details ------------------------------ Product description: 5mm (1/4 inch) closed cell polyethylene foam sandwiched between WATERPROOF METALIZED REFLECTIVE FILM on both sides.Heating and cooling costs are about 60% of the average American Household energy bill. The most effective way to cut these cost is to lower the amount of heat transferred into the home in the summer an out of the home in the winter. Our Radiant Barrier/Reflective Insulation is made from double-sided 99% aluminum foil, with closed-cell polyethylene foam. It provides optimal protection by reflecting up to 97% of radiant energy, in addition to resisting conductive and convective heat transfers.