As awareness of green homes and energy efficiency is heightened, one of the items homeowners may have questions about is the efficiency of their home’s windows.
Windows provide homes with light, warmth, and ventilation, but they can also negatively impact a home’s energy efficiency. Energy costs can be reduced by installing new, energy-efficient windows in a home, but if it’s a matter of a tight budget, energy-efficient improvements to existing windows can also help. Both of these measures reduce heating and cooling bills and lower greenhouse gas emissions.
New Energy-Efficient Windows
If a home has very old and/or has inefficient windows, it might be more cost-effective to replace them than to try to improve their energy efficiency. New, energy-efficient windows eventually pay for themselves through lower heating and cooling costs, and sometimes even lighting costs. Improving window performance in a home involves design, selection, and installation.
High-performance windows not only provide reduced annual heating and cooling bills, they also reduce the peak heating and cooling loads. According to the Efficient Windows Collaborative, the use of high performance windows can help in reducing HVAC equipment sizing. Cold glass can create uncomfortable drafts as air next to the window is cooled and drops to the floor. Also, strong direct sunlight through window onto people and interior surfaces can cause overheating and discomfort.
The following terms may be useful when choosing new windows:
- U-factor (U-value) measures the rate of heat loss, or how well a product prevents heat from escaping. U-factor ratings generally fall between 0.20 and 1.20. The lower the U-factor, the greater a product’s resistance to heat flow and the better its insulating value.
- R-value is the insulating value, which is the opposite of a U-factor. Window R-values usually range from 0.9 to 3.0.
- Low-E (low-emittance) coating can be applied to glazing surfaces to reduce heat loss, improving both heating and cooling performance.
- Solar heat gain coefficient (SHGC) measures how well a product blocks heat caused by sunlight. The SHGC is expressed as a number between 0 and 1. The lower the SHGC, the less solar heat it transmits.
Improving Existing Windows
The energy efficiency of existing windows can be improved by adding storm windows, caulking and weatherstripping, and using window treatments or coverings. Adding storm windows can reduce air leakage and improve comfort, and caulking and weatherstripping can reduce air leakage around windows. Use caulk for stationary cracks, gaps, or joints less than one-quarter-inch wide, and use weatherstripping for building components that move, such as doors and operable windows. Windows treatments and coverings can reduce heat loss in the winter and heat gain in the summer. Most window treatments, however, aren’t effective at reducing air leakage or infiltration.
To encourage energy-efficient homes, some utility companies offer rebates for home improvements such as new windows. Check with your local utility company to find out about rebates and to ensure you purchase qualifying products. See more by clicking here.
For further information about windows, check out www.efficientwindows.org or www.windowratings.org.
Feel free to contact me with any questions about energy-efficient homes, as well as for any of your real estate needs.