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Insulating Windows

Windows can be one of your home's most attractive features. Windows provide views, natural light, 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). When it comes to energy-efficiency, a single-pane glass window is little better than an open hole in your wall. Also, the more windows you have, the less efficient your home is. Improving them is a good idea; however, you can only improve them so much while still keeping them transparent and pretty.

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 may offset some of the cost of installing more efficient windows because they may 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. Insulating your windows makes them much greener, as well as keeping out dust and noise.

Cold-Climate Window Tips

Double-pane windows with low-e coating on the glass reflect heat back into the room during the winter months.

Warm-Climate Window Tips

Installing, high-performance windows will improve your home's energy performance. While it may take many years for new windows to pay off in energy savings, the benefits of added comfort and improved aesthetics and functionality may make the investment worth it to you. Many window technologies are available that are worth considering.

Shopping Tips for Windows

In temperate climates with both heating and cooling seasons, select windows with both low U-factors and low SHGCs to maximize energy savings.


Adding another layer of glass more than doubles the R-value of the window, but that’s still not great.

Window Treatments and Covering

You can choose window treatments or coverings not only for decoration but also for saving energy. Some carefully selected window treatments can reduce heat loss in the winter and heat gain in the summer.

Low-Emissivity Windows

Also called Low-E, this glass has a clear coating that retards heat.


Reflective film, like you see on some office buildings, can reduce heat infiltration to 15% of that of a normal window.