Windows are a major part of the envelope, often making up as much as 25% of the exterior walls. Windows are a main source of energy transfer. While being concerned about the insulation and building materials, many homeowners overlook the importance of windows. Often windows are chosen for merely aesthetic or immediate cost reasons. Yet, windows account for up to 25% of the typical home’s heating load in cold climates and up to 50% of the cooling load in hot climates.

High performance windows can improve energy efficiency of homes in cold weather by minimizing heat loss and, in hot climates, by minimizing solar heat gain. Many technological advances have been made that significantly enhance energy efficiency. These technologies include new frame materials and designs, low-emissivity and/or solar control coatings, low conductance gas fills, double paning, and insulating spacers between glazings. While, these new technologies can make the initial cost of windows higher for the buyer, the cost savings in energy is substantial.

The Department of Energy’s Energy Efficiency and Renewable Energy website discusses different window technologies and their savings in depth.