DuPont claims that its RoofLiner synthetic roofing underlayment offers a number of advantages over conventional felt. For starters, a single 48-inch by 250-foot roll weighs about the same as a roll of 30-pound felt but covers five times the surface area. In addition, it repels water and resists mold growth better than typical roofing felt, the company says, and offers superior tear and UV resistance. The membrane is approved for slopes of 2/12 or greater and can be used in high-wind zones as long as the proper fastening schedule is followed. It costs about $155 per roll. DuPont, 800/448-9835, dupont.com