Where the heat escapes
The Department of Energy estimates that air leaks around doors and windows account for 25 to 30 percent of heating and cooling energy loss in a typical home. Most of this leakage is invisible: gaps under doors, around window frames, where pipes and wires penetrate walls, and at the attic hatch.
Weatherstripping around door and window frames and a door sweep at the bottom of exterior doors are the highest-value, lowest-cost upgrades. Materials cost a few dollars per door and installation takes less than an hour.
Sealing the gaps that do not move
Caulk seals gaps in surfaces that do not move: where trim meets walls, where pipes penetrate exterior walls, around window frames, and at foundation joints. Use exterior-grade silicone or polyurethane caulk for outdoor applications; paintable latex caulk for interior trim.
Check existing caulk annually. Cracked, peeling, or missing caulk lets air and moisture in. Remove old caulk completely before applying new.
The biggest return on investment
If your home has fewer than 10 to 14 inches of attic insulation, adding more is typically the single highest-return energy upgrade. Heat rises, and an under-insulated attic loses heat continuously in winter and absorbs it in summer.
The Department of Energy's insulation calculator at energy.gov provides recommended R-values by climate zone and home type.
- Air leaks account for 25-30% of energy loss
- Weatherstripping + door sweeps are highest-value, lowest-cost fix
- Caulk around non-moving joints: trim, pipes, window frames
- Check and replace cracked or missing caulk annually
- Attic insulation: aim for 10-14 inches minimum
- Weatherstripping — DOE weatherstripping guidance and material selection.
- Insulation — DOE insulation recommendations by climate zone.