South Island retrofit specialists for over 20 years. We slot high-performance double-glazed glass into your existing timber or aluminium frames
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Confirm your quote this July or August and we'll upgrade your LowE Standard glass to LowE Advanced at no extra cost — a meaningful real-world improvement in warmth, comfort and UV protection.
*For all valid quotes confirmed in July and August 2026. Subject to availability.
Get a free quote →Most older Nelson homes were built with single-pane windows that bleed heat in winter, bake rooms in summer, and let UV fade everything they touch. Retrofit double glazing fixes all four — without ripping out your existing frames.
Single glazing loses heat ~10× faster than insulated walls — that's heat you've paid to make.
Cold glass meets warm room air → water on every sill. Mould, rotted joinery, ruined curtains.
UV rays bleach timber, fabric and art. Thermoglaz blocks ~80% of UV transmission.
Heating a leaky home in a South Island winter is expensive. Less heat escaping = less heating needed.
Whatever your existing window frames are made of, we have a proven retrofit system to upgrade them to modern thermal performance without ripping them out.
A pioneering, reliable process: we remove your existing single-glazed panes from your timber windows and doors, then install new high-performance thermally insulated double-glazed glass into your existing frames.
We install Thermoglazed units into any existing aluminium frame — any size, shape or finish. The most professional and reliable retrofit system on the market, guaranteed to stand the test of time.
Built around minimal disruption to your home. Most installs are wrapped within a day or two.
We come to you, measure every window, check frame condition, and explain your options. No pressure, no obligation.
You get a clear, itemised quote covering glass type, frame work, and installation. Finance options available.
Your new double-glazed units are made specifically for your frames — including leadlight, colonial bars or coloured glass.
Our team arrives, removes the old glass, fits the new units, and tidies up. Most jobs done within 1-2 days.
We walk you through every window, check operation, and answer questions. You're not done until you're happy.
Workmanship and product warranty as standard. Site Safe and WGANZ accreditation behind every job.
Our free online calculator gives you an annual savings estimate based on your home's size, frame type and current insulation — then you come straight back and lock in your spot.
Opens on thermoglaz.co.nz in a new tab. Come back here when you're done to book your free assessment.
The team at Thermoglaz have been great to deal with. Andrea was super friendly, helpful and thorough when measuring, quoting and discussing options. Ratu and his co-worker were friendly and speedy with the install. The final product is great and would definitely recommend.
Right from the start Scott was fantastic at walking me through all the options. Ratu and the team carried out exemplary work — having had a bad install previously, I can see such a difference. Incredibly impressed by the care and time gone into my new double glazing. Wouldn't even bother looking elsewhere.
Thermoglaz did a great job at retrofitting our aluminium windows as well as installing full replacements. Despite our house already being fully insulated, the double glazing has certainly increased the warmth and comfort of our home, as well as noticeable noise reduction. Great to work with from quote through to installation.