Other alternatives are made of a polyurethane foam insulation core - offering six times the energy efficiency of wood - faced on both sides with vinyl or aluminum. These typically cost for a 6-foot-wide door. All well-made nonwood home doors are designed with thermal breaks (separations between indoor and outdoor surfaces that block the conduction of heat or cold.) Glazing options Of course, the largest part of a glass sliding design door is glass. To make a door truly energy efficient, high-performance glazing is key. Fortunately, this is standard with most high-quality sliders. You''ll find double-paned glass with low-E (low energy) coating and, in some cases, argon gas filling. Low-E reduces heat transfer and protects against ultraviolet damage; argon gas filling provides greater insulation. Some manufacturers let you specify home the glazing you want when you order. Where sun-caused fading or damage can e a serious problem, you may want to opt for glass with a solar bronze or solar gray tint to reject ultraviolet rays. In addition, some companies offer decorative stained or beveled glass design with true brass caming (leading). For bathrooms or other places where privacy is a concern, obscure glass is available.

Beautifully detailed supplies, Classic-Craft and Fiber-Classic doors look and feel just like wood. Their durable fiberglass surface features a rich red oak grain, but unlike wood doors, they won''t split, dent, or warp. Plus, they''re backed by a lifetime-limited warranty. And, there''s Smooth-Star -- the new fiber glass Steel-Beater door. When comparing fiber glass Smooth-Star doors to steel, the differences are dramatic -- better looks, better feel, better performance and twice the warranty of steel doors.For 35 years, Therma-Tru Doors and systems have been synonymous with quality and innovation. Innovative manufacturing techniques and a sixth sense of market trends make Therma-Tru the nation''s leading manufacturer of fiberglass and steel doors. Fiberglass is the home future, and smart, forward-thinking builders agree that Therma-Tru has the doors they need now and for the future.

Now the nation''s leading producer of steel doors, Therma-Tru helped build the market for that product category. The effectiveness of that pioneering effort is reflected in the market share steel currently holds. For the past two decades company has focused its commitment to quality fiberglass and innovation on doors, the fastest-growing segment within the exterior door category. We were interested in differentiating ourselves from the rest of the market -- that''s the only way to be profitable in the long term recalling hiscompany''s motivation for pursuing fiberglass. Therma-Tru recruited a ream of engineers and assigned them the mission of developing a new product that would put perform both wood and steel. The team blended fiberglass and resins to invent a sheet-molding compound, as well as the tooling to transform those supplies into a door skin. After extensive laboratory and field testing, the fiberglass industry''s first door hit the market: the Fiber-Classic.