DuPont Building Products. RoofLiner is a lightweight synthetic roofing underlayment designed to offer protection against leaks and resistance to mold growth. Made from Elvaloy AC copolymer, the product is engineered for use with all types of roofs, including asphalt shingles, concrete, and standing seam metal. Available in 48-inch-wide, 250-foot-long rolls. 800.448.9835.