High-R Windows

Highly insulating windows to reduce conductive heat gains and losses

High-R Windows

Windows in the United States cause buildings to consume approximately 2 quads a year in heating energy, which is approximately one-third of all building space heating energy use and the largest single end use attributable to windows. Even if all existing windows were replaced with today’s ENERGY STAR low-e products (U-factor less than 0.35 Btu/hr-ft2-°F), window-related heating would still be over 1 quad (or 1x1015 Btu).

Because heating loads are strongly tied to conductive losses, technologies that lead to lower window U-factors are the key to reducing heating energy. A 0.1 Btu/hr-ft2-°F or R10 window is targeted as a product, which will meet the requirements of zero-energy homes. Current strategies used to reduce heat loss through windows are triple or quadruple glazing (which adds significant weight) or suspended films (which are costly). In collaboration with industry, LBNL researchers are investigating the use of non-structural center glazing layers, highly insulating window frames and spacers, and low-cost krypton gas to achieve cost and performance targets.

Contact