Windows include typical single- double- or triple-paned residential fenestration, as well as commercial building glazing. Windows are generally less efficient than walls, and are also a common site for air infiltration. Energy-efficient windows can save 7-15% of residential energy. However, good windows are expensive, and are generally less cost-effective than other efficiency measures.

Research, policies, and programs related to windows can be found in the links below and to the right. For specific efficiency tips and guidance on residential windows, click here.