Windows to the world

An energy auditor uses an infrared camera to look for areas around the window that are leaky or poorly insulated.

Homeowners looking to replace older, drafty windows to improve their home’s energy efficiency should examine all their options. New windows are often the most costly and least cost-effective energy efficiency investment you can make. There are, of course, sound reasons besides energy efficiency to invest in new windows, such as comfort, resale value, aesthetics, and even need.

Anyone considering window replacement should first think about end goals. If reducing energy costs is important, the investment in new windows ought to be weighed against other energy efficiency opportunities. An energy audit by a qualified professional is the best way to compare options.

Windows may not be the problem

The auditor can perform a diagnostic test to determine if old windows actually leak air. These tests often show that windows, even old ones, are not as leaky as they might seem, and that more significant air leakage happens elsewhere in the home. Storm windows or drapes can reduce heat loss (or gain) through the windows.

But if new windows are necessary, homeowners have a number of choices. Double-pane windows usually meet code, but the additional cost for triple-pane windows could be worth the investment in an area with extreme temperatures. Argon or Krypton gas between the panes also adds efficiency.

Take a look at low-E

Low-emissivity coating also can be added to the glass. “Low-e” coating reflects heat back into the interior space, which reduces heating bills and increases comfort.

The efficiency of the overall window is measured by its U-factor, which assesses the heat loss of the entire window. Lower U-factors are more efficient. The window framing material, the number of layers of glass, and the special coatings on the glass all contribute to the overall U-factor.

Another simple measure is to look for is the ENERGY STAR label. Only windows that are substantially more efficient than standard code requires receive that label.

Pay attention to the installation

Working with a professional is important. A poor installation can result in long-term damage, such as moisture problems that can create mold, mildew, and wall rot, which can prevent the window from operating properly or cause paint to peel.

Bids for new windows vary a great deal, so it’s worth requesting more than one and comparing qualifications, as well as price, for something that will change the look and comfort of your home for many years.

Pat Keegan and Brad Thiessen write for Collaborative Efficiency, an energy communications company.