Not all windows created equal. The best windows for your home will depend on where you live in the US and the weather and climate that are common in that region. For example, if you live in the northeastern US, you will need windows that can stand up to very cold winters, potentially very hot summers, occasional super storms and hurricanes, and lots of rain and snow. If you live in the southwest, you will need windows that can tolerate intense sun, very dry conditions, and cool nights.
The US Environmental Protection Agency’s ENERGYSTAR program has established different energy efficiency guidelines for windows and doors depending on where they’ll be used. Windows that will be installed in a wet, cold climate must meet different energy efficiency standards than windows that will be used in a hot, dry climate. However, all ENERGYSTAR qualified windows, doors, and skylights must be independently tested, certified, and verified according to test procedures established by the National Fenestration Rating Council.
Like the appliances that show an Energy Guide label so consumers know how much energy their refrigerator will use, qualified windows will show an NFRC label that provides performance ratings in five categories: U-Factor; Solar Heat Gain Coefficient (SHGC); Air Leakage (AL); Visible Transmittance (VT); and Condensation Resistance.
The U-Factor indicates how well the window insulates; the lower the number, the better the insulation. The SHGC shows how well the window blocks sunlight; again, the lower the number, the better. The AL measures how quickly air passes through the window’s joints. The lower the AL value, the less air leaks into your home. VT measures how much light the window lets through. The higher the VT, the more light you’ll see. Finally, condensation resistance reflects how well the window resists water build-up. The higher the number, the better, because that means less build-up that the window will allow. (ENERGYSTAR offers specific numerical ranges for all factors here.)
When buying windows from a local contractor, the contractor should know which windows are the best qualified and most energy efficient for your region. If you are buying windows on your own, look for an ENERGYSTAR label that shows the window has been certified to meet the requirements of what EPA calls your “climate zone.” The label may either be a map that shades the states where the windows will provide energy efficiency benefits, or it may carry a statement like “ENERGYSTAR Certified in all 50 States.”
How did purchasing climate-specific windows change the comfort levels in your home? What about your utility bills? Share with us in the comments below!