Storm window guide · Energy
How much energy do storm windows save?
What the U.S. Department of Energy's own research found, without the sales pitch.
What the research found
The Department of Energy had the Pacific Northwest National Laboratory test low-E storm windows. Three findings matter for a house in the Midwest:
- About 10% a year in test homes. In two identical test homes, the one with exterior low-E storm windows added over its existing double-pane windows used about 10.5% less heating energy and 8% less cooling energy, an estimated 10% over a typical year (PNNL Lab Homes study).
- More in cold climates. PNNL's modeling of homes across the country put heating and cooling savings higher in colder climate zones like Iowa's than in mild ones (PNNL-24826).
- Low-E makes the difference. The low-E coating adds savings over a clear-glass storm window (DOE Building America Solution Center).
Your result depends on your windows, your house and your heating fuel. Older, leakier windows generally have the most to gain.
Why it works
A storm window traps a layer of still air in front of your window. Still air insulates, so less heat leaks out in winter and less comes in during summer. Add Low-E glass and an invisible coating reflects heat back where it came from.
Fit matters as much as glass. Because we build each storm window to your measured opening, it closes off the drafts a stock size leaves behind.
Questions
Do storm windows really save energy?
Yes. In side-by-side test homes run for the U.S. Department of Energy, adding exterior low-E storm windows over the homes' existing double-pane windows cut heating and cooling energy by an estimated 10% over a typical year. Computer modeling by the same lab found larger savings in cold climates.
Is Low-E worth it in a storm window?
Usually. The Department of Energy research found the low-E coating adds meaningful savings over clear-glass storm windows, and it does it without darkening the view. See how Low-E works.
Do storm windows stop drafts?
They help. A well-fitted storm window closes the gaps around an older window from the outside. Ours are built to the opening, with woolpile weatherstrip on the inserts and a sill expander at the bottom.
See what Low-E costs on your windows.
Tick Low-E in the instant quote to see what it adds to your windows.