U.S. Department of Energy: Energy Efficiency and Renewable Energy

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Windows

Windows can be one of your home's most attractive features. Windows provide views, daylighting, ventilation, and solar heating in the winter. Unfortunately, they can also account for 10% to 25% of your heating bill. During the summer, your air conditioner must work harder to cool hot air from sunny windows. Install ENERGY STAR windows and use curtains and shade to give your air conditioner and energy bill a break. If you live in the Sun Belt, look into low-e windows, which can cut the cooling load by 10% to 15%.

If your home has single-pane windows, as many U.S. homes do, consider replacing them with new double-pane windows with high-performance glass (e.g., low-e or spectrally selective). In colder climates, select windows that are gas filled with low emissivity (low-e) coatings on the glass to reduce heat loss. In warmer climates, select windows with spectrally selective coatings to reduce heat gain. If you are building a new home, you can offset some of the cost of installing more efficient windows because they allow you to buy smaller, less expensive heating and cooling equipment.

If you decide not to replace your windows, the simpler, less costly measures listed here can improve their performance.

Cold-Climate Window Tips

Illustration shows how a double-pane window with low-e coating keeps hot air inside by reflecting heat  back into the room.

Cold-Climate Windows Keep Heat In
Double-pane windows with low-e coating on the glass reflect heat back into the room during the winter months.

Illustration shows how a double-pane window with spectrally selective coatings prevents heat coming in from the outside and allows light to come inside.

Warm-Climate Windows Keep Heat Out
In the summertime, the sun shining through your windows heats up the room. Windows with low-e coatings on the glass reflect some of the sunlight, keeping your rooms cooler.

Warm-Climate Window Tips

Long-Term Savings Tip

Shopping Tips for Windows

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Content Last Updated: 1/22/2009