The U.S. Department of Energy says that in a typical residential or commercial building, about 42 percent of energy is lost through doors, roofs, attics, walls, floors, and foundations. In the winter, windows can account for 10 to 25 percent of a home’s utility bill through heat loss. To address these energy losses, the Energy Department is investing $9 million in building envelope technologies, including high-efficiency windows, roofs, and heating and cooling equipment.
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