What the government numbers say
ENERGY STAR estimates that certified low-e storm windows save about 10 percent on annual heating and cooling bills when installed over single-pane clear glass windows. The U.S. Department of Energy reports that a low-e storm window over a low-performing window can reduce a home's heating and cooling costs by 10 to 35 percent. Real savings depend on your climate, your existing windows and how well the new panel fits.
Read about energy-efficient storm windowsWhy an added panel makes a difference
A storm window adds a second layer of glass and a pocket of air between the panel and your original window. That layer slows heat moving through the glass, and a snug perimeter seal cuts the air that leaks around an old sash. Made-to-measure panels help because the seal only works when the frame matches your opening.
See how to measure your openingLow-e glass versus clear glass
Low-e glass has a thin coating that reduces heat loss through the glass when it is cold outside. ENERGY STAR notes that some low-e products also limit incoming heat in summer. Clear glass storm windows still add a layer and cut drafts; low-e glass adds a coating on top of that. Our aluminum Low-E windows are built around that coating.
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Storm windows versus replacing every window
The Department of Energy describes low-e storm windows as costing about a quarter of what full window replacement costs while delivering similar energy savings. A storm window also keeps your original windows, which matters in older and historic homes where the frames and glass are part of the character.
Compare storm windows and replacementWhat changes your result
Single-pane windows with loose sashes gain the most. A tight, well-maintained double-pane window gains less. Check that the original frame is sound before adding a panel, measure at the mounting position, and choose a style that matches how your window opens. Savings figures are national estimates, not a promise for a specific house.
Shop storm windows by typeSavings go beyond the glass
ENERGY STAR notes that its savings estimates do not include the additional savings from reducing air leaks in older windows, which vary substantially from house to house. A snug storm window helps close the gaps around an old sash, so the real benefit can be larger than the glass numbers alone suggest.
Read about energy-efficient storm windowsWhere to start in your home
Begin with the windows that feel the draftiest, the single-pane windows, and the rooms you use most. A simple test is to hold your hand near the sash on a windy day. Add storm windows to those openings first, then work through the rest as your budget allows.
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