Drafty Window Cost Calculator
Estimate yearly heat-loss cost of a single leaky window — and what fixing it saves.
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Visible gap, pencil-width crack ≈ 1 sq in. Rattling sash with daylight ≈ 4-8 sq in.
Typical winter average: 25-35°F.
Gas ~$15, propane ~$30, electric resistance ~$50.
Yearly cost
$7
Air leakage
4.0 CFM
Daily cost
$0.04
What this means
Air infiltration through a leaky window adds heat loss on top of conduction loss through the glass itself. A single visibly-leaky double-hung can cost $40-$120/year in cold climates — and most homes have several.
Most leakage isn't the glass: it's around the sash, between the frame and rough opening, and at the meeting rail. All of these are DIY-fixable for a few dollars per window.
How to lower this cost
- Add V-strip weatherstripping in the sash channels — fixes the biggest leak in old double-hungs.
- Caulk between the window frame and the trim/wall.
- Apply shrink-film window insulation kits — cuts both drafts and conduction loss.
- Use a sash lock to pull the meeting rail tight (not just for security).
- Replace failed weatherstripping on casement windows — usually a $10 part.
Next step
Tally leaks across the whole house
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Results are estimates based on typical conditions. Actual costs vary by climate, utility rates, equipment efficiency, and home characteristics. Use them as a starting point — for precise figures consult a qualified energy auditor or your utility company. Estimates are not a guarantee, and any work you do on your home is at your own risk — we are not liable for installation errors or property damage. Air sealing a home with gas, oil, propane, or wood-burning appliances can cause backdrafting and carbon monoxide risk — get a combustion safety test and keep CO alarms working. See our Disclaimer.