Energy efficient windows

By Miranda Boutelle September 2023

Adding efficiency to your windows will add year-round comfort and savings to your home

Line art showing suns heat reflecting off windowUpgrading or improving your windows is an important component of your home’s energy efficiency. There are several options for improving your windows, ranging from replacement windows to storm windows to budget-friendly repairs.

Window efficiency

Start by identifying the kind of windows you have. Are they single pane or double pane? Are the frames metal, wood or vinyl? Some manufacturers etch the make and model numbers in a corner of the glass, so you can look up the manufacturer for more information.

Several components can make windows more efficient. High-quality frame materials insulate and reduce heat transfer. Two or more panes of glass with space in between (filled with air or gas) improve the window’s insulation capability. Warm edge spacers hold the panes of glass the proper distance apart and help insulate the edges of the panes. Low-emissivity coatings applied to the glass can reflect infrared light, keeping the heat in during the winter and out during the summer.

Single-pane windows and double-pane windows with metal frames are the least energy efficient. The lower the efficiency of your existing windows, the higher the potential for energy savings.

Window efficiency is rated in U-factor and Solar Heat Gain Coefficient, or SHGC. U-factor measures heat transfer through the window, which relates to how well it insulates. The lower the U-factor, the more efficient the window. The SHGC measures how effectively the window blocks heat from the sun.

closeup on woman's hand locking window
According to U.S. Department of Energy, heat gain and loss through windows consumes 25% to 30% of residential heating and cooling energy costs. | Courtesy photo

Replacement and maintenance

If you want to replace your existing windows, I recommend shopping for ENERGY STAR®-certified windows. ENERGY STAR® sets specific U-factor and SHGC requirements based on your geography, so you get the best fit for your location. The window industry has been impacted by price increases over the past few years, so keep in mind, this can be an expensive upgrade.

Storm windows are a lower-cost solution for some homes. Low emissivity storm windows have energy savings similar to replacement windows at about a third of the cost. Storm windows are mounted to the interior or exterior and are available in operable styles, so you can still open and close your windows.

If you want to maintain the historic architecture of your existing windows, low-e storm windows are a great option. Some companies can refit your existing window frames with custom double-pane glass and weatherstripping.

If new windows or storm windows are not in the budget, your best bet is to maintain your existing windows. Keep the paint and caulking on the exterior in good condition. Caulk around the inside trim, ensure sash locks are installed properly and seal tight when locked. There are a variety of weatherstripping types for windows to keep drafts at bay.

Whether you replace or make improvements to what you have, adding efficiency to your windows will add year-round comfort to your home.

Category: Efficiency

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