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Windows are responsible for 25–30 percent of residential heating and cooling energy use and are an important consideration for both new and existing homes.

If you are selecting windows for new construction, it's important to choose the most efficient windows you can afford that work best in your climate.

About 40 percent of residential windows on existing homes in the United States are single-pane windows. If your existing windows are single pane, taking steps to reduce the energy loss through windows can make your home more comfortable and save you money on energy bills.

You have three broad options if you hope to reduce the amount of energy lost through your windows and improve the comfort of your home:

  1. Improve the efficiency of your windows
  2. Retrofit your windows
  3. Replace your windows.

Improving the Efficiency of Your Windows

If your windows are in good condition, taking steps to improve their efficiency may be the most cost-effective option to increase the comfort of your home and save money on energy costs.

Cold Weather Window Tips

  • Install tight-fitting, insulating window shades on windows that feel drafty after weatherizing. Consider insulated cellular shades, which are “honeycombed” and can be raised or lowered. Obtain energy efficiency ratings for window attach­ments from the Attachments Energy Rating Council.
  • Close your curtains and shades at night to protect against cold drafts; open them during the day to let in warming sunlight.
  • Apply low-e film on the inside of your windows to keep heat from radiating out. Films are rated by the NFRC and will be rated by the AERC.
  • Alternatively, install low-e exterior or interior storm windows, which can save you 12–33 percent on heating and cooling costs, depending on the type of window already in­stalled in the home. They should have weatherstripping at all movable joints; be made of strong, durable materials; and have inter­locking or overlapping joints.
  • Repair and weatherize your current storm windows, if necessary.

Warm Weather Window Tips

  • Install white window shades, drapes, or blinds to reflect heat away from the house. It is always best to install exterior shades whenever possible
  • Close curtains on south- and west-facing windows during the day.
  • Install awnings on south- and west-facing windows to create shade.
  • Apply sun-control or other reflective films on south-facing win­dows to reduce solar heat gain. In hot climates, consider adding them to east, west, and south-facing windows.

Retrofit Your Windows

With any retrofit, it is important to ensure proper installation and air tightness. Following the retrofit, you may want to take additional steps to ensure efficiency by caulking and weatherstripping and adding window coverings and treatments.  

Even the most energy-efficient window must be properly installed to ensure energy efficiency. Therefore, it's best to have a professional install your windows.

Windows should be installed according to the manufacturer’s recommendations and be properly air sealed during installation to perform correctly. To air seal the window, caulk the frame and weatherstrip the operable components.

Selecting New Energy-Efficient Windows

Before selecting new windows for your home, determine what types of windows will work best and where to improve your home's energy efficiency. It's a good idea to understand the energy performance ratings of windows so you’ll know what energy performance ratings you need for your windows based on your climate and the home's design.

For labeling energy-efficient windows, ENERGY STAR® has established minimum energy performance rating criteria by climate. However, these criteria don't account for a home's design, such as window orientation.

If you're constructing a new home or doing some major remodeling, you should also take advantage of the opportunity to incorporate your window design and selection as an integral part of your whole-house design—an approach for building an energy-efficient home.