Insulated Window Glazing or Glass
Insulated window glazing refers to windows with two or more panes of glass. They are also called double-glazed, triple-glazed, and—sometimes more generally—storm windows.
To insulate the window, the glass panes are spaced apart and hermetically sealed to form a single-glazed unit with an air space between each pane of glass. The glass layers and the air spaces resist heat flow. As a result, insulated window glazing primarily lowers the U-factor, but it also lowers the solar heat gain coefficient. (See energy performance ratings for windows, doors, and skylights for more information on these terms.)
Some window manufacturers use spacers—which separate two panes of glass—that conduct heat less readily than others. These spacers can further lower a window's U-factor.
Other technologies window manufacturers use to improve the energy performance of insulated glazing include these:
Learn More
Financing & Incentives
Find Federal Tax Credits for Energy Efficiency
Energy Savers
Product Information
Residential Windows, Doors, and Skylights
ENERGY STAR®
Product Ratings
National Fenestration Rating Council
Department of Energy Resources
Highly Insulated Window Technology
Lawrence Berkeley National Laboratory
Related Links
Window Technologies: Low Conductance Spacers
Efficient Windows Collaborative
