Our STS Pro-Shield Plus Liner has multiple functions. One of the best functions is, being used as a Heat Shield in crawl spaces or basements for floors above. By stapling the liner, foil side facing up towards the floor, the foil will reflect the radiate heat back up into your home. Keeping your floors warmer and lowering you energy costs. This Great Option is one that saves you money year around. Not allowing the heat to penetrate your floors during the summer will help keep your cooling cost down as well. See "TAX CREDIT CERTIFIED" for more info!!! Liner is sold by the roll only, so mix the 50' and 125' roll sizes to get the closest square footage required! Note: Don't forget to add extra for cuts and obstacles.