Windows can 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 new solar control spectrally selective windows. Spectrally selective windows can cut the cooling load by 10% to 15%.

If your home has single-pane windows consider replacing them. New doublepane windows with high-performance glass are available on the market. In colder climates, select doublepane windows that are gas filled with low emissivity coatings on the glass to reduce heat loss. In warmer climates, select doublepane 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 doing so allows you to buy smaller, less expensive heating and cooling equipment.

Cold climate window tips

  • Use a heavy-duty, clear plastic sheet on a frame or tape clear plastic film to the inside of your window frames during the cold winter months to help reduce leakage of warm air.
  • Install tight-fitting, insulating window shades on windows that feel drafty after weatherizing.
  • Close your curtains and shades at night; open them during the day.
  • Keep windows on the south side of your house clean to let in the winter sun.
  • Install exterior or interior storm windows.
    • Storm windows can reduce heat loss through the windows by 25% to 50%.
    • Storm windows should have weatherstripping at all moveable joints; be made of strong, durable materials; and have interlocking or overlapping joints.
    • Low-e storm windows save even more energy.

Warm climate windows keep heat out

In the summertime, the sun shining through your windows heats up the room. Windows with spectrally selective coatings on the glass reflect some of the sunlight, keeping your rooms cooler.

Warm climate window tips

  • install white window shades, drapes, or blinds to reflect heat away from the house
  • close curtains on south- and west-facing windows during the day
  • install awnings on south- and west-facing windows
  • apply sun-control or other reflective films on south-facing windows to reduce solar gain

Shopping for windows

  • Look for the ENERGY STAR
  • When you’re shopping for new windows, look for the National Fenestration Rating Council label
    • This means the window’s performance is certified
  • Remember, the lower the U-value, the better the insulation.
    • In colder climates, a U-value of 0.35 or below is recommended.
      • These windows have at least double glazing and a low-e coating
  • In warm climates, where summertime heat gain is the main concern, look for windows with double glazing and spectrally selective coatings that reduce heat gain.
  • Select windows with air leakage ratings of 0.3 cubic feet per minute or less.
  • In temperate climates with both heating and cooling seasons, select windows with both low U-values and low solar heat gain coefficiency (SHGC) to maximize energy benefits.
  • New windows must be installed correctly to avoid air leaks around the frame.
    • Look for a reputable, qualified installer.