An installer directory & savings field-guide for NZ homes
Warmer rooms. Drier windows. Lower power bills.
Plain-English double glazing for Kiwi homes — retrofit your existing timber sashes or swap out the whole frame. Real numbers on what it saves, real installers in your region.
- Retrofit · full-frame · IGU only
- WANZ-aligned specs
- Independent — installers don't pay to be listed
The field calculation
What would it actually save you?
Move the sliders. The arithmetic isn't a quote — it's a single-variable estimate of the heating-cost saving and condensation reduction you'd see on a typical NZ heat-pump-warmed home. The full assumptions are open at the bottom.
Heat-Loss Savings Estimator
Section 3 · Field calculation
Thermal verdict
$162
estimated annual heating saving
Condensation verdict
Largely eliminated on normal nights
In Wellington, the inside-pane temperature lifts comfortably above dew point on most winter nights. The exception is high-humidity rooms (ensuite-adjacent bedrooms, kitchens after cooking) — those still need the existing extractor habits.
Get matched to installers →Show the assumptions and the maths▸
Inputs to the model
- U single (base): 5.8 W/m²K
- U single (this house): 6.2 W/m²K
- U double (retrofit IGU): 2.8 W/m²K
- Total glazed area: 15.0 m²
- Heating degree-days: 1450
- Heat pump COP: 3.5
- Electricity price: $0/kWh
The arithmetic
Heat through glass per year (kWh) = (Usingle − Udouble) × area × HDD × 24 / 1000. We then divide by heat-pump COP to get electricity, then multiply by price. Single-variable model — assumes the room is heated to a constant 18°C through the heating season and ignores solar gain (which works in your favour) and air leakage (which doesn't). It is a ballpark for a "should I bother" conversation, not a quote.
The directory
A few installers worth knowing
Different regions, different work. Heritage retrofit specialists, marine-zone aluminium pros, alpine triple-glazing crews. Browse the full directory by region.
Tasman Glazing Ltd
Tasman Glazing
Long-established Auckland retrofit specialist — drops sealed IGUs into existing timber sashes without replacing the frame.
Mt Wellington
- Retrofit IGU
- Timber joinery
- Heritage
Kōwhai Window Co Ltd
Kōwhai Window Co
North Shore full-frame replacement — aluminium joinery for 70s/80s brick-and-tile, with marine-grade coatings for the coast.
Albany
- Full-frame
- Aluminium joinery
- Thermally broken
Isthmus Glass Ltd
Isthmus IGU
IGU manufacturer first, installer second — supplies units to the trade and direct to homeowners.
Penrose
- Retrofit IGU
- Full-frame
- New build
Harbour Thermal Glazing Ltd
Harbour Thermal
Glazing-and-air-sealing combined — treats Wellington's wind-driven heat loss as a single package.
Wellington Central
- Retrofit IGU
- Timber joinery
- Heritage
By region
Find an installer near you
Seven NZ regions, each with the local installers and a regional brief on what's distinctive about glazing there.
Why this directory
The wrong installer will sell you the wrong window — confidently.
Double glazing isn't one product. Retrofit, full-frame, IGU spec, frame thermal-break, climate-zone targeting — installers specialise. Matching the work to the installer is the whole job.
01
Retrofit, not replacement
Most NZ villas and 80s timber-framed houses can keep the original sashes — the installer routs out the existing rebate and drops in a sealed double-glazed unit. Half the cost of full-frame replacement, often a stronger result if you care about character.
02
Built for the Kiwi housing stock
Solid timber pre-1978 cottages. Aluminium-joinery 80s/90s tract homes. Architecturally-spec'd 2000s+ builds. Each has a different right answer — and the wrong installer will sell you the same answer regardless.
03
Honest payback maths
We won't tell you double glazing pays for itself in 5 years — it usually doesn't, on heating savings alone. The real returns are comfort, condensation, resale and noise. We say so.
04
H1-aware specs
Quotes call out U-values, spacer type (warm-edge vs aluminium), gas fill (argon vs air), low-E coating direction — the things that actually decide whether you meet the 2022 H1 schedule.
The field guide
Reading before you ring around
Practical NZ-specific writing on the questions that decide whether your renovation is worth the spend.
Field guide · 7 min · 26 April 2026
Retrofit vs full-frame double glazing in a NZ villa
Routing IGUs into the original timber sashes versus ripping the joinery out. What costs more, what looks better, and why the answer is usually retrofit — for a villa.
Read the chapter →
Field guide · 6 min · 26 April 2026
Will double glazing actually fix condensation on your bedroom windows?
Short answer: usually yes, but only if you also fix the underlying humidity. The longer answer is more useful — here's why some double-glazed windows still drip.
Read the chapter →
Field guide · 6 min · 26 April 2026
What does double glazing actually cost in NZ in 2026?
A real cost breakdown for the three common NZ scenarios — single-room retrofit, whole-house retrofit, whole-house full-frame replacement — with the line items installers don't always volunteer.
Read the chapter →
Get matched
Send us your brief.
Tell us about your house — age, region, what you're trying to fix (warmth, condensation, noise). The brief is forwarded to two or three installers matched to that specific work in your H1 climate zone, with responses inside two working days.
- Editorial directory — listings are not pay-to-place
- Two to three quotes, not eight — matched to the work
- Vetted against GBI registration and WANZ standards
Get matched to 2–3 installers
Brief form
Tell us about your house and what you're trying to fix — warmth, noise, condensation. We'll send you to installers who actually do that work in your region.