Seal Leaks: The $50 Fix Contractors Charge $800 For
Air sealing beats new windows for ROI. Focus: attic hatch perimeter, recessed lights, plumbing penetrations, crawl space rim joist. Fire-rated foam + acoustical sealant under $50.
Before you spend $15,000 on new windows, spend $50 on air sealing. A Department of Energy audit typically finds that attic air leakage costs 15-25% of a home’s heating and cooling bill. Windows are often under 10%. The math is not close.
Where the leaks actually are
1. Attic hatch perimeter — almost always wide open. Weatherstrip it and add R-10 foam board on top of the hatch door.
2. Recessed can lights — older IC-rated cans leak air like a screen door. Install airtight LED retrofit modules or cover from the attic side with an airtight enclosure.
3. Plumbing penetrations — every pipe through the top plate is a chimney. Fire-rated spray foam seals the gap.
4. Crawl space rim joist — the band joist where the floor meets the foundation. Two-inch rigid foam board cut to fit between the joists, sealed with spray foam at the edges. This is a 4-hour job and it changes how the downstairs feels in January.
5. Bathroom fan housing — most builder-grade fans are not airtight. Caulk the housing to the ceiling drywall and insulate above the fan.
Tools
Great Stuff Fireblock spray foam ($6/can), acoustical sealant ($8/tube), caulk gun, headlamp, knee pads, kitchen trash bag to kneel on. Total: under $50. Four hours of your Saturday, one full winter of lower bills.