Hobbies and Crafts What type of front door is most energy-efficient? What type of front door is most energy-efficient? fiberglass exterior doors What is a eco friendly door? Sustainable Doors A good exterior door will fit tightly and use the best available weather-stripping technology. The most energy-efficient doors are made of fiberglass or wood-clad steel, or painted steel, filled with a core of polyurethane foam.