Great panes
A guide to energy-efficient windows and what to look for when shopping
HOME MAINTENANCE
Heat gain or loss through windows accounts for 25% to 30% of our home's heating and cooling energy use. Drafty windows in your house can lead to higher utility bills and inconsistent indoor temperatures. Both factors force your home's HVAC system to work overtime to maintain a comfortable temperature, leading to higher energy costs.
Switching to energy-efficient windows can address these costly problems when done correctly.
What makes a window energy-efficient?
Glass type, coating, gas fills and frame materials are things to prioritize when shopping for new windows. You'll also want to consider where you live and your home's orientation, as certain features benefit different climates and sun exposure.
The best energy-efficient windows feature multiple panes of glass filled with an inert gas — typically argon or krypton — that further insulates the window. Wood, fiberglass and composite frame materials usually are the most energy-efficient, depending on your climate and willingness to maintain them.
Next, consider the coating. Windows with a low-emissivity coating or film cost more, but may reduce energy loss by 30% to 50%. Different low-e coatings are designed for hot or cold climates and can even control the amount of visible daylight that comes through your windows.
An often overlooked aspect of energy efficiency is installation.
"You can buy the highest quality windows on the market, but a poorly executed installation can undermine the energy efficiency benefits," says Kiril Ratia, founder of Ratia Construction.
Ratia says that if a window installer or a carpenter uses the wrong-size nails, they can puncture the window's sealing mechanism. A good installer also should place insulation around the window, add flashing tape, put weather stripping around the sashes and finish the seal with caulk. Anything that compromises the seal of the window and the opening it fills will lead to drafts.
Understanding energy ratings and labels
Window energy ratings and labels guide buyers to make the best choice, but they can feel overwhelming at first. Here's a quick breakdown of common energy ratings and labels — and what to look for.
■ A U-factor rating provides insight into a window or door's energy efficiency by measuring its heat transfer through the glass and glazing. The lower the number, the better.
■ Solar Heat Gain Coefficient is the amount of solar radiation transmitted or absorbed through a window, glass door or skylight. The lower the SHGC rating, the better the product is at shading and the less solar heat it transmits. A window with a higher SHGC rating keeps heat in the home during the winter. Choose windows with an SHGC rating that best suits the climate and your home's orientation.
■ Visible transmittance is a performance rating measuring the fraction of visible sunlight entering your home through the window. This rating ranges from 0 to 1, with 0 indicating that no visible light enters the home. Typically, higher VT ratings are ideal because they reduce the amount of electric lighting your home needs during the day.
■ Air leakage ratings measure how much air seeps into your home through a closed window. Look for windows with a low air leakage rating, as this indicates greater energy efficiency.
■ Energy Star certifications, managed by the U.S. Environmental Protection Agency, indicate that a product is energy-efficient. Use the Energy Star Climate Zone Finder to match the window type to your home's climate zone.
Lowering energy costs
Energy-efficient replacement windows decrease the amount of heat your home loses in winter and help keep it cooler in summer. If you live in a colder climate, a gas-filled, low-e window helps reduce heat loss. Homeowners in warmer climates should prioritize windows with a solar-control film or coating to keep their homes cool.
Energy Star-certified windows, for example, can save homeowners up to 13% on energy bills when replacing single-pane windows. If your electric bill is about $150 per month, this is a savings of about $234 per year.
If you notice rising energy costs, drafts or condensation between window panes, consider caulk or weatherstripping to update existing windows, or replace them entirely for the best results.
Ideally, replace all of your windows at once (especially if they're the same age), or work room by room to target the worst offenders.
Costs and considerations
Window costs vary significantly based on the window materials, installation team and energy-efficiency features. Most homeowners can expect to pay between $400 and $1,500 per window, with the higher end of the range reflecting premium wood, fiberglass or composite windows.
In terms of return on investment, experts say homeowners can expect long-term results in several ways.
"Homeowners can typically expect to recoup 60% to 70% of their window investment at resale, but the real payback begins immediately through reduced energy bills," says Phil Adkins, president at Adkins & Sons, a home improvement contractor. "In my experience, most families notice a meaningful reduction in their utility expenses within the first year, particularly in regions with harsh winters or hot summers where HVAC systems work overtime."
