Energy Efficient Windows

Windows bring light, warmth, and beauty into buildings and give a feeling of openness and space to living areas. They can also be major sources of heat loss in the winter and heat gain in the summer. However, when properly selected and installed, windows can help minimize a home's heating, cooling, and lighting costs.

Reducing heat loss or gain in homes often includes either improving existing windows or replacing them. Low-cost options available for improvement are caulking, weatherstripping, retrofit window films, and window treatments. Replacing windows will involve the purchase of new materials, which should adhere to certain energy efficiency standards.

Different combinations of frame style, frame material, and glazing can yield very different results when weighing energy efficiency and cost. For example, a fixed-pane window is the most airtight and the least expensive; a window with a wood frame is likely to have less conductive heat loss than one with an aluminum frame; double-pane, low-e window units are just as efficient as triple-pane untreated windows, but cost and weigh less.

No one window is suitable for every application. Many types of windows and window films are available that serve different purposes. Moreover, you may discover that you need two types of windows for your home because of the directions that your windows face and your local climate. To make wise purchases, first examine your heating and cooling needs and prioritize desired features such as daylighting, solar heating, shading, ventilation, and aesthetic value.

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This document was produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (NREL), a DOE national laboratory.

NOTICE
This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

Content provided by the U.S. Department of Energy