🔧 Skill Level: Beginner
Quick Answer
Air leaks are invisible but can account for 25-40% of heating and cooling losses in Melbourne homes. Find them with an incense stick or smoke pen, then seal with silicone caulk and weatherstripping. Most homes can be sealed in a half-day for under $50. Autumn is the best time — before heating season starts.
What You’ll Need
- Incense stick or smoke candle (reveal air movement)
- Caulking gun ($10-20 at Mitre 10)
- Paintable caulk (acrylic or silicone, $8-15 at Bunnings)
- Weatherstripping tape ($20-50 for whole house)
- Expanding foam for large gaps ($12-20 at Bunnings)
- Draught stoppers for doors ($15-30)
- Torch/headlamp for dark areas
Where Air Leaks Hide in Melbourne Homes
Most Melbourne homeowners focus on windows and doors, but in SE Melbourne’s brick veneer and weatherboard homes, the worst leaks are often in unexpected places. A systematic room-by-room hunt takes about an hour and identifies $200-400 in annual heating savings.
Top leak locations by priority:
- Where walls meet the ceiling (ceiling rose gaps, cornice cracks)
- Around electrical outlets and light switches on external walls
- Under skirting boards on external walls
- Around penetrations (pipes, conduits, cables entering walls)
- Attic hatch/manhole edges
- Around exhaust fans and rangehood ducting
- Door frames and window frames (gap between frame and wall)
Step-by-Step: Finding and Sealing Air Leaks
- Choose your detection method: On a cold, windy day, close all windows and doors. Light an incense stick or smoke candle. Hold it near suspected leak points — smoke will drift toward leaks. Alternatively, run your hand slowly along surfaces to feel cold air movement.
- Check external wall outlets first: Remove electrical outlet covers (turn off power at switchboard first). Hold incense behind the outlet. Many older homes have no insulation or seal behind power points — cold air flows freely from the wall cavity.
- Check the ceiling perimeter: Hold incense near where the wall meets the ceiling along external walls. Gaps in cornice or plaster allow heated air to escape directly into the roof space.
- Check door and window frames: Run incense around the full perimeter of each external door and window frame — not just the opening edge, but where the frame meets the wall.
- Seal small gaps (under 5mm): Apply paintable caulk for wall/ceiling gaps and around frame perimeters. Smooth with a wet finger. Allow 24 hours to cure before painting.
- Seal medium gaps (5-20mm): Use flexible silicone or backer rod + caulk. For gaps around pipes, use fire-rated silicone if near any heat source.
- Seal large gaps (over 20mm): Use expanding foam, allow to cure, then trim flush and caulk over for a neat finish.
- Seal doors: Install weatherstripping on door frames and draught stoppers at the base. Test by closing door and checking for visible light gaps.
Room-by-Room Checklist
| Room | Key Leak Points | Best Fix |
|---|---|---|
| Living room | Skirting boards, cornice gaps, fireplace (if unused) | Caulk skirting; seal fireplace damper or block flue |
| Bedroom | External wall outlets, window frames, cornice | Outlet foam gaskets; frame caulk |
| Kitchen | Rangehood duct, under-sink pipe penetrations | Flexible silicone around penetrations; backdraft damper on rangehood |
| Bathroom | Exhaust fan, pipes through tiles, door gap | Silicone around fan; door weatherstrip |
| Roof/attic | Manhole edges, recessed downlights, ceiling penetrations | Foam tape on manhole; downlight covers |
When to Call a Professional
If you find significant air movement through internal walls (indicating missing wall insulation), gaps in the building envelope (subfloor, eaves), or if the house has major draughtiness despite sealing visible gaps, an energy auditor can do a blower door test ($300-500) to precisely identify all leaks. Ask about the Victorian Energy Upgrades program — audits may qualify for rebates.
Tips & Gotchas
- Safety warning: Always turn off power at the switchboard before removing outlet covers. Never apply foam or caulk near active electrical components. Use fire-rated silicone near heat sources.
- The best time to detect leaks is on a cold, windy winter day when the pressure difference is greatest. Autumn is ideal — you feel the difference immediately after sealing.
- Unused fireplaces are enormous air leaks — a standard open flue is like leaving a window open 24/7. Install a chimney balloon ($40-70 at Bunnings) if you don’t use it.
- Outlet foam gaskets ($5 for a pack of 10 at Bunnings) are one of the highest ROI air sealing products. Install behind every outlet on external walls.
- Don’t seal bathroom and kitchen exhaust fans — these need to vent. Instead, ensure they have backdraft dampers so air doesn’t flow in when they’re off.
Frequently Asked Questions
How much can I save by sealing air leaks?
Typically 15-30% on heating and cooling bills. Melbourne homes with older construction (pre-2000) commonly have enough leakage to waste $300-600/year in heating costs. Payback on sealing materials is usually under 3 months.
Will sealing air leaks cause moisture problems?
Only if you seal too aggressively without mechanical ventilation. Modern building codes require controlled ventilation. For typical Melbourne homes with exhaust fans and some natural ventilation, aggressive air sealing is safe and beneficial.
What’s the difference between air sealing and insulating?
Insulation slows heat transfer; air sealing stops air movement. Both are needed — insulation without air sealing still allows wind-washing (air moving through or around batts), reducing their effectiveness by up to 50%.
Local Resources (SE Melbourne)
- Bunnings Warehouse – Caulk, expanding foam, draught stoppers, outlet gaskets
- Victorian Energy Upgrades – Rebates for draught-sealing and insulation
- YourHome.gov.au – Government guide to airtightness and insulation
