Fixing Drafty Windows: What to Do When Windows Leak Air
Drafty windows undermine home comfort and push heating and cooling bills higher. Most fixes cost under $50 and take an afternoon.
Windows are responsible for 25–40% of heating and cooling energy loss in a typical Australian home. Air leaks through gaps in window frames, failed weatherstripping and deteriorated seals make this worse. The good news: most window air leaks are fixable without replacing the window itself.
Why Drafty Windows Cost You Money
When cold air infiltrates in winter or hot air enters in summer, your heating and cooling system works harder and runs longer. In a poorly sealed home, your reverse cycle system may effectively be conditioning the outdoor air — a constant energy drain. Draught sealing is one of the most cost-effective interventions available to Australian homeowners.
How to Detect Window Air Leaks
- On a cold windy day, hold a damp hand near window edges and corners — you will feel air movement
- Use a lit incense stick near window perimeters — smoke deflection indicates a draft
- Look for daylight visible around window frames — a gap you can see is a gap that leaks air
- Check for condensation or moisture staining inside window reveals, indicating air movement
Caulk vs Weatherstripping: What to Use Where
| Product | Where to use | What it does |
|---|---|---|
| Caulk / flexible sealant | Fixed gaps between window frame and wall reveal | Permanently seals stationary joints |
| Weatherstripping (foam tape) | Around openable sashes and sliding sections | Compresses to seal movable parts while allowing opening |
| Door/window draught seals | Bottom of windows and door sills | Blocks underside gaps without impeding operation |
| Window film (temporary) | Entire pane face in winter | Adds an air layer — effective but reduces visibility |
Step-by-Step Fix
- 1. Clean all surfaces — caulk and tape adhere poorly to dust and old paint
- 2. Remove old, cracked or peeling caulk — a utility knife or caulk removal tool works
- 3. Apply new flexible sealant (silicone or polyurethane) to fixed frame-to-wall gaps
- 4. Fit new weatherstripping foam tape to openable sashes
- 5. Add draught stoppers to the bottom rail of windows that do not seat tightly
When to Consider Window Replacement
- Single-pane aluminium frames in a climate zone 5–7 home (Melbourne, ACT, southern highlands)
- Visible fog or moisture trapped between panes in double-glazed units — the seal has failed
- Frames that are warped, swelling or rotting beyond repair
- Windows where drafts persist after thorough sealing and weatherstripping
Sealing air leaks around windows costs $10–$50 in materials and takes a few hours. That is typically a faster payback than any other home efficiency upgrade.