Storm windows or new windows
A low-e storm window over a sound old sash is the cheaper energy upgrade, and on the federal numbers for a climate like ours it pays back in a few winters.
Storm windows are nothing new on old Maine houses. The modern version has a low-emissivity coating, and that changes the numbers.
Low-e storm windows, modeled for a zone 6 city
PNNL, one of the Department of Energy's national laboratories, modeled low-e storm windows in cities across the country. The nearest in our climate zone is Burlington, Vermont (climate zone 6A):
| Measure | Result |
|---|---|
| Site energy savings, over single-pane windows | 19 percent |
| Savings-to-investment ratio | 3.2 |
| Simple payback | 4.8 years |
| U-factor improvement | 0.88 down to 0.36 with a low-e storm outside a single-glazed wood double-hung, and 0.51 down to 0.28 outside a double-glazed one |
Low-e glass over clear glass in a storm window paid back in 2 to 5 years in every zone studied.
Against replacement windows
ENERGY STAR's own modeling for the Northern zone puts a whole-house replacement at about $568 a year saved over single-pane glass and about $282 a year over older double-pane. Those are whole-house figures for a typical two-story house; a partial replacement saves proportionally less, and the price of the windows is not in them at all.
Rebates
When we checked Efficiency Maine's residential rebate list in October 2026 it covered heat pumps, heat pump water heaters, insulation, wood and pellet boilers, geothermal, electric vehicles, batteries, clothes washers and circulator pumps; it had no rebate for windows or doors. Its own winter tips suggest storm windows, window film or indoor inserts to cut heat loss through old glass.
When a storm window is the wrong answer
- When the sash or frame is rotten.
- When a bedroom window fails the escape rule and has to change size.
- When condensation between an old sash and its storm keeps the sill wet; a storm needs weep holes at the bottom.
- When you want the house to look different.
In a historic district a storm window has one more advantage: Yarmouth's review rules, for one, treat storm windows as reversible alterations that need no review.
Where this comes into the work
Sources: pnnl.gov · energystar.gov · efficiencymaine.com · efficiencymaine.com · yarmouth.me.us
Common questions
Interior or exterior storm windows?
Will storm windows stop drafts?
Do old triple-track storms count?
Not sure your windows are worth keeping?
We will look at the sashes and frames and tell you.
Get a free estimate →