Draughts are one of the most common — and most fixable — reasons Kiwi homes feel cold and damp in winter. Uncontrolled air leakage lets your expensive heating escape and draws in cold, moist outside air. The good news is that finding and sealing draughts is mostly a straightforward DIY job that can make a real difference to your comfort and power bills.
Why Draughts Matter in NZ Homes
New Zealand's older housing stock — particularly pre-1970s timber homes — was built with little thought for airtightness. Gaps around joinery, under doors, and through subfloor vents can add up to a surprisingly large total opening. BRANZ research consistently shows that draught-sealing is one of the most cost-effective home improvements you can make, often paying for itself quickly through reduced heating costs. Under the Healthy Homes Standards, rental properties must also meet draught-stopping requirements, so landlords have a legal obligation to address significant gaps.
How to Find Draughts
Before you can fix a draught, you need to find it. Here are the most reliable methods:
The Hand Test
On a cold, windy day, slowly move your hand around window frames, door frames, skirting boards, cornices, wall penetrations (pipes, cables), and the ceiling. You'll often feel a cool flow of air.
The Incense or Smoke Test
Hold a lit incense stick near suspected gaps. Watch for the smoke to waver or be drawn sideways — that indicates moving air. Keep away from curtains and flammable materials.
The Torch Test (at Night)
Have a helper shine a torch along the outside of window and door frames while you watch from inside in a darkened room. Light leaking through reveals gaps.
Common Draught Locations
- Gaps under external doors — often the biggest single source
- Around window frames — especially older timber sash and casement windows
- Skirting boards and cornices — where walls meet floors and ceilings
- Fireplace flues — open fireplaces are a major heat loss point
- Subfloor vents and access hatches
- Penetrations for pipes, cables, and ducting
- Ceiling hatches and recessed downlights
Choosing the Right Draught-Sealing Product
Different gaps need different solutions. Here's a quick guide:
| Location | Recommended Product | Notes |
|---|---|---|
| Under external doors | Door bottom seal or door sweep | Choose one rated for the gap size |
| Door frames (sides/top) | Foam or rubber compression strip | Self-adhesive types are easiest |
| Window frames | V-strip or foam tape | Match to gap width |
| Skirting/cornice gaps | Paintable acrylic sealant (caulk) | Flexible, can be painted over |
| Pipe/cable penetrations | Expanding foam or silicone sealant | Use fire-rated foam near flues |
| Fireplace flue (unused) | Chimney balloon or flue blocker | Removable if you use the fire |
Products for all of the above are widely available at Bunnings and Mitre 10. PlaceMakers is another good option for trade-quality sealants and weatherstripping.
Step-by-Step: Sealing Common Draughts
Sealing Under a Door
- Measure the door width carefully.
- Choose a door bottom seal or brush-style door sweep to suit the gap size.
- Clean the door bottom thoroughly.
- Cut the seal to length with a hacksaw or tin snips.
- Fix with the screws provided, adjusting so it makes light contact with the floor without dragging heavily.
Applying Compression Weatherstrip to Door and Window Frames
- Clean the rebate (the surface the door or window closes against) with a damp cloth and allow to dry.
- Cut self-adhesive foam or rubber strip to length.
- Peel and press firmly into the rebate, working around the full perimeter.
- Test the door or window closes properly — it should feel slightly firmer but not difficult to shut.
Caulking Skirting Boards and Cornices
- Use a flexible, paintable acrylic sealant (not silicone, which can't be painted).
- Load a caulking gun and cut the nozzle at a slight angle.
- Run a neat bead along the gap.
- Smooth with a damp finger or caulking tool.
- Allow to cure before painting.
Sealing an Unused Fireplace
A chimney balloon is an inflatable plug that sits inside the flue, blocking cold air. They're removable if you ever want to use the fireplace again. Always attach the reminder tag so nobody lights a fire with the balloon in place.
Ventilation: Don't Over-Seal
This is important: draught-sealing is not the same as blocking all ventilation. Your home still needs controlled fresh air for healthy indoor air quality and to manage moisture. Subfloor vents, for example, should generally be kept clear to prevent dampness under the house. If you're sealing a very airtight home, consider a heat recovery ventilation (HRV) system. Energywise has good guidance on balancing warmth with healthy ventilation.
When to Call a Professional
Most draught-sealing is well within DIY reach. However, consider calling a qualified handyman or builder if:
- Gaps are large or structural — significant gaps in cladding or around window flashings may indicate weathertightness issues that need a proper assessment.
- You suspect subfloor or roof space problems — working in confined spaces carries safety risks.
- Recessed downlights need sealing — these require fire-rated covers and the work must not compromise electrical safety. Any work on the light fittings themselves is restricted electrical work and must be carried out by a registered electrician licensed under the Electrical Workers Registration Board (EWRB).
- You're not confident with the results — a professional can do a thorough audit and seal the home systematically.
You can find trusted local handymen and builders in your area at tradedirectory.co.nz.