Modern windows have a lot of technology behind them. They have features like insulated frames, triple panes, gas-filled cavities and protective coatings - all for the sake of boosting energy efficiency, which saves money on home heating and cooling.
However, be cautious when you hear a salesman refer to energy efficient windows. Anyone can call a window energy efficient, but precise government standards dictate which windows are actually energy efficient. Keep in mind, too, that climate affects energy efficiency. A window that is considered energy efficient in Arizona likely won’t be in Maine.
Shopping for energy efficient windows can be confusing. There are all sort of acronyms for various measures of energy efficiency, from SHGC to VT to LSG. But you don’t have to be a scientist to make sense of it all.
First, only consider windows that are certified by Energy Star, a federal program that helps consumer identify energy efficient products and appliances. Replacing old windows with Energy Star-certified windows can decrease your energy bills by up to 15 percent. Prior to shopping, use Energy Star’s climate zone search tool to identify the minimum criteria for windows in your region. Both Pella and Andersen windows are Energy Star-certified.
You should also familiarize yourself with the National Fenestration Rating Council (NFRC), the nonprofit that tests Energy Star products. The NFRC places a label on all Energy Star windows with various measures of energy efficiency, including:
- U-factor: How well a product prevents heat from escaping. The ratings usually range between 0.15 and 1.2. The lower the U-factor, the better.
- Solar Heat Gain Coefficient (SHGC): How much heat from the sun is blocked. SHGC is measured as a number between 0 and 1, with lower numbers blocking more solar heat. In warm climates, lower numbers are usually better. In cold climates, higher numbers are better.
- Visible Transmittance (VT): How much light comes in through the window. This is also expressed as a number between 0 and 1. The higher the VT, the more light that comes through.
- Air Leakage: How much outside air is able to enter the home through the window. This rate usually falls between 0.1 and 0.3. Unlike the first three, however, this is an optional rating. Manufacturers can choose to forgo it.
- Condensation Resistance: Another voluntary rating measuring how well a window resists condensation. This is expressed as a number between 1 and 100, with higher numbers better able to resist condensation.
Understanding how various window frame materials affect energy efficiency can also be helpful in making your decision. Read the Energy.gov window type guide for more information about the pros and cons of materials like vinyl, aluminum, wood, fiberglass and composite.
Energy efficient windows range in price from about $200 to several thousand dollars, depending largely on the window frame material. The level of energy efficiency also has an impact on price, as do local installation costs.
Nationwide, the average cost of a complete window replacement ranges from $7,000 to $20,000, according to Consumer Reports. Presumably, the average includes windows that are not Energy Star certified. However, energy efficient features such as argon gas between panels and low-E glass are becoming more standard.
Looked at another way, energy efficient windows are usually 10 to 20 percent more expensive than regular windows. However, labor should not be more expensive. Be sure to ask for a detailed breakdown of costs to make sure.
There are financial incentives to installing energy efficient windows, aside from the savings on your energy bills. The federal government offers a $200 tax credit, which has been extended through 2013, and many utility companies offer rebates.
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