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
- You can 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. Remember, the plastic must be sealed tightly to the frame to help reduce infiltration.
- 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 movable joints; be made of strong, durable materials; and have interlocking or overlapping joints. Low-e storm windows save even more energy.
- Repair and weatherize your current storm windows, if necessary.
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.
Long-Term Savings Tip
- 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.
Efficient windows may have two or more panes of glass, warm-edge spacers between the window panes, improved framing materials, and low-e coating(s), which are microscopically thin coatings that help keep heat inside during the winter and outside during the summer.
Shopping Tips for Windows
- Look for the ENERGY STAR label.
- Check with local utilities to see what rebates or other financial incentives are available for window replacement.
- High-performance windows have at least two panes of glass and a low-e (low emissivity) coating.
- Remember, the lower the U-factor, the better the insulation. In colder climates, focus on finding a low U-factor.
- Low solar heat gain coefficients (SHGCs) reduce heat gain. In warm climates, look for a low SHGC.
- In temperate climates with both heating and cooling seasons, select windows with both low U-factors and low SHGCs to maximize energy savings.
- Look for whole-unit U-factors and SHGCs, rather than center-of-glass, or COG, U-factors and SHGCs. Whole-unit numbers more accurately reflect the energy performance of the entire product.
- Have your windows installed by trained professionals. Be sure they’re installed according to manufacturer’s instructions; otherwise, your warranty may be void.