How can one coating keep heat out in summer and keep it in during winter?

It sounds like a contradiction, but it isn’t. The coating works like a mirror for infrared heat, reflecting it back toward where it came from. In summer, the sun’s heat is near-infrared coming from outside, so it’s reflected away and rooms stay cooler. In winter, your home’s warmth is long-wave far-infrared radiating off your heater, walls, furniture and the people inside, and the coating reflects that back inside instead of letting it escape. It’s one consistent behaviour; the season just changes which direction the heat is coming from. Some heat still passes through the glass by conduction, so it reduces heat transfer rather than stopping it completely.

Is a glass coating as good as double glazing?

No single coating fully matches double glazing’s insulation, and we say so openly. Thermal Glass Coat’s strength is that it targets radiant (infrared) heat and UV directly, installs in as little as half a day with no building work, and costs a fraction of retrofit glazing — making it the practical choice when double glazing is too expensive or disruptive.

Does it work on single-glazed windows?

Yes. Thermal Glass Coat is applied to your existing single glazing and reduces the infrared heat passing through it. Some heat still transfers by conduction through single glass, so we’re happy to advise where a coating gives the best return for your specific windows.

Will it change how my windows look?

No, not noticeably. Once applied the coating is virtually clear, with only a very slight tint most people don’t notice. It doesn’t reduce your privacy or block natural light — it only cuts the infrared heat and UV you can’t see.

Does it protect against UV and fading?

Yes — Thermal Glass Coat blocks up to 99% of UV, the main cause of fading in floors, furniture, curtains and artwork. This is one area where standard double glazing offers little protection, so we’re often asked to apply the coating over existing double-glazed windows purely for UV and fading control.

How long does it last?

Thermal Glass Coat is guaranteed for 10 years against cracking, bubbling, peeling and delaminating. Because it bonds chemically to the glass rather than sticking on like film, it won’t lift at the edges over time. After 11+ years of applications in New Zealand we have had no instances of the coating breaking down, and in Japan it has been in use for 15+ years with no signs of breakdown.

How long does installation take and how messy is it?

Most homes are completed by a trained technician in half a day to two days, depending on the size of the job, with minimal noise and mess and no building work. You may need to move some furniture away from the windows.

Does it help with condensation?

Yes, it can help — but it will not stop condensation. By keeping the inner surface of the glass closer to room temperature, the coating reduces how much moisture condenses on your windows. How much depends on your home’s humidity and ventilation.

Glass coating or window film — what’s the difference?

Both are optical treatments on your existing glass, but a coating bonds chemically to the glass while film is a separate laminate held on by adhesive. The bonded coating is virtually clear, harder-wearing, and won’t bubble, peel or delaminate at the edges — the most common way stick-on film fails. Film can be cheaper up front and comes in heavy-tint or removable versions, so it may suit renters or anyone wanting dark privacy tint.

Does window film reduce heat loss?

Some window films reduce radiant heat and UV, but results vary a lot by product — darker tint films are more effective at reducing heat loss, while cheaper films are often UV-only. High-end films give thermal and UV performance similar to Thermal Glass Coat, though the coating is usually lower cost and more durable. On single glazing, heat still transfers by conduction through the glass regardless of the film. A bonded glass coating works on the same principle but is more durable. We’re happy to give you an honest assessment of what either can realistically achieve on your specific windows.

Where is Thermal Glass Coat available in New Zealand?

We serve Auckland, the Waikato, Bay of Plenty and Hawke’s Bay. Call 0274 810 686 or email admin@thermalglasscoat.co.nz for a quote.

Will the coating make my rooms darker?

No, not noticeably. The coating lets most of the visible light through — typically we see only an 8–10% drop in light, which most people never notice. Your rooms stay bright and naturally lit, while the coating quietly cuts the infrared heat and UV you can’t see anyway. That’s the whole idea: keep the light, lose the heat.

Does tinted glass do the same thing?

Not really. Tinted glass can reduce heat, but it does it by darkening the room — you trade away your natural light to get there. Thermal Glass Coat works differently: it lets the natural light in while still blocking up to 99% of UV and up to 90% of the infrared heat. So you get the heat and fade protection without living in a dimmer home.

How should I clean the coated glass?

Easy — and we’ll give you a printed “Aftercare” guide when we finish. The short version: use a soft microfibre cloth with warm water, then dry it off with a clean dry microfibre cloth. That’s it. Don’t use detergents or cleaning sprays on the coated glass.

How much solar energy does the coating block?

On ordinary clear glass, the coating rejects a meaningful share of total solar energy — conservatively around 45–50%, and often more depending on the type of glass. Within that, it blocks up to 90% of infrared (the heat you feel) and up to 99% of UV (the light that fades your furnishings). The exact result depends a lot on the specific glass being treated, and in practice we usually see better than these figures.

How thick is the coating?

Very thin — an average of about 7 microns, compared to most window films at around 40 microns. Because it’s so thin and bonds into the glass rather than sitting on top like a laminate, there’s no film edge to catch, lift or peel.

Is the coating scratch-resistant? How hard is it?

Yes. The cured coating is hard-wearing — up to around 4.5H on the pencil-hardness scale, which is harder than typical window film. Normal cleaning with a soft cloth won’t mark it.

Is the coating fire-resistant?

The cured coating is combustion-resistant.

If the glass breaks, will the coating hold it together?

No — and it’s important to be clear about this. Thermal Glass Coat doesn’t change the safety rating of your glass. If a pane is designed to break a certain way under impact, it still will. The coating is about heat and UV performance, not safety glazing, so it’s not a substitute for safety or laminated glass where that’s required.

Is there any glass that can’t be coated?

Yes, a few types. The coating can’t be applied to already-coated or treated glass surfaces — that includes the coated side of reflective glass and low-E glass, the treated side of frosted glass, the printed side of decorative glass, and wire glass and laminated glass. If you’re not sure what you’ve got, we can check for you before quoting.

Is it an interior or exterior coating?

It’s mainly applied to the inside of your glass, though it can be used on the outside in certain situations. We’ll advise which suits your windows when we assess the job.

Can it be applied over existing tinted film?

No. Any existing film needs to come off first, so the coating can bond directly to the clean glass surface. We can talk through removal if your windows are currently filmed.

What’s the smell during and after application, and is it safe?

The liquid contains solvents, so there’s a smell while it’s going on and as it cures — but it dissipates once the coating is touch-dry (usually within a couple of hours), especially with ventilation or windows open. If you’re sensitive to smells, we’d suggest staying out of the room during application and for a few hours afterwards.

It’s a liquid coating — how do you stop dust settling in it?

Good question, and it’s something we manage carefully. Before applying, we turn off fans and ventilation that could stir up the air. During prep we wipe down the joinery beside the glass with a damp cloth to settle any dust, and we work off lint-free drop sheets wherever possible. Getting the humidity balance right helps too. A quick dust and vacuum by you before we arrive is always appreciated and makes a real difference.

Do you need to remove the glass from the frames?

No. It’s all done on site, with the glass staying right where it is in the frames.

How much glass can you coat in a day?

As a rough guide, a two-person team covers around 20 square metres per day — though it varies with the size of each window, how easy the glass is to access, and the weather on the day.

More technical detail

For anyone who wants the deeper technical answers, expand the sections below.