Draught Stopping NZ Homes Winter 2026: The $50–$300 Fix That Beats Cranking the Heater

Your first post-1-May power bill is about to arrive, and it's not going to be pretty. Contact lifted daily charges from 1 May, Genesis has raised retail prices an average of 12.8% from 16 May, and Meridian has flagged up to 7%. At the same time, the wind has turned southerly and most NZ homes are about to discover — yet again — just how leaky they really are.

If you can't afford a $5,000 insulation retrofit before July, there's one thing you can do this weekend that will genuinely move the needle: stop the draughts. For $50–$300 of bits from Bunnings or Mitre 10 and an afternoon's work, you can cut heat loss by 15–25% in a typical pre-2000 Kiwi home. That's a bigger return per dollar than almost any other upgrade, and unlike batts or wall cavity fill, you don't need an installer, a subsidy application, or a permit. You just need to know where to look.

At a Glance

Total realistic spend for a determined weekend DIYer: $150–$300. Realistic first-winter saving: $100–$200 on heating, plus a noticeably warmer house.

Why NZ homes are so draughty

New Zealand has some of the worst-built homes in the developed world for air-tightness. Roughly 70% of our housing stock predates the 2007 Building Code update, built with single-glazed timber joinery, gaps under skirtings, holes in the ceiling for downlights, and fireplace flues venting straight to the sky. (For the full backstory, see our complete home insulation guide.)

The result: in a typical 1960s–1990s NZ house, the entire volume of air inside is replaced by outside air somewhere between 5 and 15 times per hour during a southerly. Every one of those air changes is air you've already paid to heat. Insulation slows the heat that conducts through surfaces; draught stopping slows the heat carried away by air. Different problems — and the second one is far cheaper to fix.

Step 1 — find the draughts

You can't seal what you can't find. Pick a windy day (NZ being NZ, this should not be hard), shut all the doors and windows, turn off any extractor fans and ventilation systems, then walk slowly around the inside of the house.

The hand test. Run the back of your hand slowly along the frames of every window and external door, around the edges of skirting boards, around recessed downlights, behind power outlets on external walls, and around the ceiling hatch into the roof space. Cold spots tell you where the air is moving.

The candle or incense test. A lit candle, a stick of incense, or a smoking match held about 50mm from a suspected gap will visibly drift sideways when there's airflow. This is the most reliable cheap diagnostic — better than your hand, because human skin only registers air movement when it's a couple of degrees colder than ambient.

The thermal-camera test. If you've got a phone-clip thermal imager ($150–$300 from Bunnings or AliExpress), the cold streaks around windows and doors are obvious. Most homeowners don't need one — but if you're trying to convince a sceptical partner, this is the quickest way.

Where to look first in a pre-1990 NZ home, in rough order of impact:

1. The fireplace. An unused open fireplace is a metre-wide vertical hole in your house. Even an "old chimney we never use" can be responsible for 10–20% of a home's total air loss.
2. External door bottoms. Stand outside and look at the gap between the door and the threshold. If you can see daylight, the air is also moving.
3. Sash and timber-joinery windows. Pre-1990 timber windows lose their bead seals over time. Rattle the sash gently — if it moves at all, air is moving with it.
4. Recessed downlights. Particularly older non-IC-rated kind, which vent to the ceiling space by design. Each one is the rough equivalent of a 50mm hole punched through your insulation.
5. Ceiling hatch. Frequently a thin sheet of MDF sitting on a timber frame, with no seal. Roof-space air is typically 5–10°C colder than living-space air in winter.
6. Ranchslider and bi-fold tracks. The brush seals wear out within 5–10 years and most homeowners never replace them.
7. Skirting boards, architraves, and power outlets on external walls. In older homes there's often a continuous gap behind these connecting directly to the wall cavity or subfloor.
8. Old vents that no longer make sense. Wall-mounted extractor fans with broken dampers, redundant subfloor vents cut into the floorboards, dryer vents that no longer close.

Step 2 — fix them, by budget tier

Tier 1: $0 — what to do today

• Close internal doors to rooms you're not heating. The heat-pump-runtime savings from heating two rooms instead of five at the same temperature are enormous, regardless of how leaky the house is.
• Pull curtains as soon as the sun is off the windows. A heavy lined curtain pulled tight to the frame is genuinely equivalent to about half a millimetre of glass-fibre batt. Curtains pooled on the floor seal better than curtains stopping above the sill.
• Put a rolled-up towel along the bottom of any door that whistles. It's not pretty, but it's free, and it works while you wait for your seals to arrive.
• Block any unused fireplace with a bin bag stuffed with old towels or blankets as a temporary measure. Just put a note on the fireplace so you remember to take it out before next time you light it.

Tier 2: $50–$150 — the Bunnings / Mitre 10 weekend

This is where most homeowners get the biggest bang for their buck. None of the work below requires a tradesperson.

Door bottom seals — $20–$40 per door. A brush seal screws to the bottom of the door so it brushes the threshold. Stormguard, Raven and the Bunnings house brand are all fine. For external doors, the heavier automatic-drop kind ($40–$60) that lifts when the door opens is the best $40 you'll spend.

Foam or EPDM tape — $5–$15 per roll. Self-adhesive strips around the inside of the door frame and opening windows so the door or sash compresses onto them. EPDM rubber lasts 5–10 years; cheap foam tape lasts 2–3 winters before it crushes flat. Buy EPDM if it's in stock.

Chimney balloon or flue block — $30–$60. An inflatable bladder wedged into the chimney throat, or a rigid foam plug for smaller flues. Leave the warning tag hanging so nobody lights the fire on it.

Letterbox brush flap — $20–$40. Replaces the existing letter slot. A surprising amount of air moves through these on windy days.

Sash window draught-proofing kit — $40–$80 per window. NZ suppliers sell DIY kits with brush carrier strips that screw into the meeting rail and stiles. Give yourself an hour per window the first time.

Downlight covers — $25–$60 each. Sit over the downlight from above and stop air pulling through. Use IC-F or fire-rated covers for any halogen or older non-LED downlight. LED downlights usually run cool enough for a non-fire-rated foam cap, but check the spec.

Skirting and architrave caulk — $10–$30. A tube of paintable acrylic gap filler and half an hour with a caulking gun. Run a bead along the gap between skirting and floor, and around any architrave on an external wall.

A realistic shopping list for a 1970s 3-bedroom house: 2 door brush seals ($60), 1 automatic drop seal for the front door ($50), 2 rolls of EPDM tape ($25), 1 chimney balloon ($45), 4 downlight covers ($120), 1 tube of gap filler ($15). Around $315, plus a Saturday afternoon.

Tier 3: $200–$500 — bring in a professional

Most NZ towns now have a draught-proofing service — search "[your city] draught proofing" or "sash window restoration" and you'll usually find two or three. A good outfit will spend half a day to a day replacing perished seals on sash windows (fiddly DIY), fitting compression seals to timber doors, and dealing with the awkward edge cases — pipe penetrations behind the laundry, the cat flap, the dryer vent that no longer dampers shut.

For a 3- to 4-bedroom pre-1990 timber home, expect $600–$1,200 all up. Draught-proofing isn't covered by Warmer Kiwi Homes, but the payback is fast enough that it doesn't really matter.

Tier 4: $1,000+ — when seals aren't enough

There's a point where draught-proofing stops being the right answer:

• Rotten timber joinery. If the rebate in your window frame has rotted out, no seal in the world will grip it. Replace or rebuild the joinery first, then seal.
• Single-glazed windows in serious cold zones. South Island and Central Plateau homes generally need to think about double glazing or window inserts in addition to draught-proofing — the conduction heat loss through single glass dwarfs the air-leak loss in those climates.
• Walls with no insulation at all. Sealing a leaky uninsulated wall just means you now lose heat by conduction instead of convection. If you've draught-proofed and the house is still cold, look at retrofit wall insulation next, or at the cheaper ceiling and underfloor options if you haven't already.

What to skip

Plastic shrink-film window kits. Cheap, but they look terrible, make windows impossible to open, and trap moisture against the glass — exactly what you don't want in a Kiwi winter.

Spray-foam everything. Expanding foam is great for specific holes around pipe penetrations, but resist the urge to use it on every gap. It's nearly impossible to remove cleanly and tends to bridge into wall cavities where it traps moisture.

Permanently blocking subfloor vents. Your subfloor needs to breathe — blocking the perimeter vents traps moisture under the house and rots the bearers. If cold air is coming up through the floor, the answer is underfloor insulation plus a vapour barrier.

"Smart" draught-stopping gadgets sold on Facebook. None of the "magic" door snakes or stick-on "thermal seals" outperform a $30 brush seal from Mitre 10.

The ventilation balance — don't seal too tight

This is the most important warning in the whole article. NZ homes are leaky for a reason: most of them have no mechanical ventilation. The same airflow costing you money in heat loss also drags out moisture from showers, cooking, drying clothes and breathing.

Draught-proof aggressively without thinking about ventilation and you can end up with the same total power bill — just spent on a dehumidifier instead of a heat pump — and a house with visibly more condensation on the windows. The fix isn't leaving the draughts; it's adding controlled ventilation. Open an upstairs window during showers, run extractor fans for 10 minutes after cooking, and dry clothes outside or in a vented dryer. If your home is already wetting up, read our breakdown of HRV, DVS and Smartvent running costs or how to stop window condensation this winter before you go further.

Useful rule of thumb: airtight enough to hold a heated room at temperature on LOW, but ventilated enough that no window has visible condensation by 7am.

Does it actually pay back?

Let's run the numbers for a typical 1970s 3-bedroom Wellington house heated by a 5 kW heat pump in the lounge and a small panel heater in the bedroom.

Before draught-proofing, the house needs about 12,000 kWh of heating input across the winter to keep the lounge at 19°C and the bedroom at 16°C overnight. Research from BRANZ and Otago consistently finds a 15–20% reduction in heating energy in older NZ homes after thorough draught-stopping. Take the middle — 17.5% — and you're saving about 2,100 kWh.

At the new average residential rate of around 35c/kWh (post 1 May, blended day and night), that's around $735 saved over a winter. Even on a conservative 10% reduction it's $420 saved. Either way, $300 of draught proofing pays back in its first winter, with change to spare, and keeps paying back every winter after that.

With Genesis up 12.8% and Contact's daily charges higher than they were two weeks ago, the value of not having to heat extra air just keeps going up.

A sensible order of operations

If you're standing in front of your house in mid-May wondering what to do, this is the priority order I'd give a sibling:

1. This weekend ($50–$300): Walk the house with a stick of incense. Fix the obvious draughts — door seals, chimney balloon, window tape, downlight covers, letterbox flap.
2. Within a month ($600–$1,200, optional): If sash windows are still rattling, book a professional draught-proofer. They'll do in half a day what would take you three weekends.
3. Before next winter ($1,500–$3,000): Check whether you qualify for Warmer Kiwi Homes subsidies and use them to get ceiling and underfloor insulation done at 80–100% off the bill.
4. The year after ($3,000–$8,000): If the house still feels cold, look at retrofit wall insulation, double glazing, or window inserts depending on your climate zone.

The point of starting with draught-stopping isn't that it's the only thing you should do — it's that it's the cheapest, fastest, most accessible step on the ladder, and on a post-1-May power bill even a $50 fix pays back fast.

Not sure which upgrade your home actually needs first? Take our free 2-minute home energy assessment — it'll tell you whether draught-proofing is your highest-ROI fix or whether bigger structural jobs are the smarter spend.

Ready to take the next step beyond DIY? Find verified insulation installers in your area and ask whether your home qualifies for Warmer Kiwi Homes coverage — for most pre-2008 NZ homes, the answer is yes.