What to look for in replacement windows.
Old-fashioned, single-pane windows are prime candidates for replacement. But even newer, double-pane windows might be failing or inadequate. Check for drafts by running a lighted candle around a window’s edge. Frost and ice buildup on the exterior of the house near doors and windows is also a sign of leakage. Finally, make sure your windows operate smoothly. It shouldn’t take effort to open and close them.
When shopping for replacements, keep in mind these considerations.
Energy efficiency: The easiest way to find efficient windows is to look for the Energy Star label—the same government-ratings system more familiarly used on appliances and electronics. In the coldest climes, the U.S. Department of Energy estimates that the average homeowner can save up to $501 and 3,839 lbs. of CO2 a year by replacing single-pane windows with Energy Star-rated alternatives.
The two most important numbers to examine are the U-factor, which measures the rate of heat loss, and the Solar Heat Gain Coefficient (SHGC), which measures how effectively the window blocks heat coming from the sun. Lower ratings are better in both instances. The most efficient windows have coatings that keep out the summer heat and reduce ultraviolet light to prevent pigments in fabrics and furniture from fading by up to 75 percent—all without reducing the amount of visible light.
Construction and installation: Replacement windows come in vinyl, aluminum, wood, clad wood or fiberglass. Each looks and performs differently—and cost varies widely. The most expensive choice is clad wood, which combines a traditional look with low maintenance and energy-efficient performance, while vinyl tends to cost the least.
When shopping, look for a sturdy frame with reinforced corners for support and thermal resistance. Water management is critical for preventing damage to the window and surrounding structure, so it should depend on flashing rather than caulking. Check that hardware and mechanisms are strong and well attached, while sashes should operate smoothly and easily. Identify the weep system (found on the bottom edge of the frame) and ensure it will drain moisture outside your house’s siding. When choosing a contractor to install the windows, look for certification by the American Window and Door Institute or Installation Masters.
Aesthetics: In the old days, windows had multiple small panes because it was prohibitively expensive and technologically unfeasible to make larger ones. With industrial glass production, the reverse is now true, and manufacturers have come up with some odd solutions to recreate the look of traditional windows, such as sandwiching the “mullions” between the sealed layers of glass.
The better models are a hybrid in which mullion bars are permanently attached to both sides of the glass, while a spacer bar is installed between the glass to cast realistic shadows. But a few national brands, including Dynamic Architectural, Marvin, Kolbe and Parrett make authentic divided lite windows, in which double-glazed panes are separated by true mullions. The only drawback? Price. Expect to pay about twice as much for this type of construction. These manufacturers—and many regional custom builders—can also build to custom specifications and designs to suit any architectural vision, modern or traditional.