Therma-Tru fiberglass doors offer the authentic look of wood. But, unlike wood, fiberglass will not warp or rot. And, unlike steel, it will not dent or rust. Built with a polyurethane foam core, Therma-Tru fiberglass doors insulate against cold and heat for exceptional energy efficiency. Discover Therma-Tru® complete fiberglass door systems that are engineered with craftsmanship to help provide weather resistance and energy efficiency.