Thermally Broken Window Installation in Dunedin – H1 Compliant Joinery for Cold Bridging

In Dunedin this is not a luxury item, it is often the only way to comply. The city sits in H1 climate zone 5, where consented residential work needs a minimum window R value of R0.50. That figure cannot be met with plain aluminium. It requires Low E glass in a thermally broken, uPVC or timber frame.

What the thermal break changes

Plain aluminium conducts heat extremely well, which is exactly what you do not want in a window frame. The frame sits close to outdoor temperature, and room air touching it drops below its dew point, so water forms on the metal.

The polyamide strip splits the frame into an inside half and an outside half that are no longer metallically connected. The inside half stays warm. The condensation stops and the whole window performs better thermally.

Where it is worth the money

South and west facing rooms, bedrooms with an existing condensation problem, and any home being renovated for warmth instead of just repaired. It costs more per opening than standard double glazed aluminium.

On a sunny north facing lounge that already runs warm, standard double glazing usually gives you most of the benefit for less. We will say so instead of quoting the dearest option everywhere.

Wind zone still comes first

Thermal performance does not override structural performance. The joinery still has to be rated to NZS 4211 for your site climate zone, and on the Dunedin hills that regularly means an Extra High rating with thicker glass and closer fixing centres.

We check the council climate zone for your address before ordering, because a beautiful warm window that leaks air at 55 metres per second has solved the wrong problem.

Where the thermal break earns its money

Rooms where it matters most

South and west facing rooms, bedrooms that already run with water on the frames, and any room that is heated in the evening and closed overnight. Those are where the temperature difference across the frame is largest for the longest.

On a sunny north facing living room that gains heat all day, standard double glazed aluminium usually gives you most of the benefit for less, and we will say so rather than quoting the dearest option everywhere.

What it does not change

A thermal break in the frame does nothing about moisture load, ventilation or an uninsulated ceiling. It stops the frame being the coldest surface in the room, which is a specific problem with a specific fix.

If every surface in the house is wet, the frame was never the limiting factor.

Our thermally broken windows process in Dunedin, step by step

Window and Glass Repair Dunedin runs joinery work to a fixed sequence, and on a Dunedin house two of those steps take longer than they would anywhere else in the country. Here is the whole thing so nothing arrives as a surprise.

1. Free measure, every opening individually

   Window and Glass Repair Dunedin measures each opening on its own rather than working from a plan. In a Dunedin villa or bungalow almost no two openings are the same, because they were made on site by hand a century ago and the house has moved since. Head, jamb and sill get checked for level and plumb and the reveal depth is recorded.

2. Establish what the Building Code requires here

   Dunedin sits in H1 climate zone 5, which carries the highest window performance requirement of anywhere in New Zealand. Window and Glass Repair Dunedin confirms at quote stage whether your job is consented work that has to meet it, or a like for like replacement that does not, because it changes the product and the price substantially.

3. Written fixed quote with the unknowns named

   Frame material, glass specification, hardware and what happens to the internal linings, all in writing. Rot behind the reveal cannot be seen until the old unit is out, so it is carried as a stated allowance with the rate shown rather than as an open ended variation.

4. Manufacture, and the real lead time

   Joinery is made to your measurements. Aluminium typically runs four to six weeks, thermally broken longer, and timber longer again. Window and Glass Repair Dunedin confirms the date in writing and books the fit around it rather than promising a start that depends on somebody else's factory.

5. Removal, and repairing what is behind

   The old unit comes out and the opening is inspected. On older Dunedin housing the bottom of the reveal is where decay concentrates, because that is where a century of condensation has run down the glass and sat. Damaged framing is repaired before anything new is fitted.

6. Fit, flash and air seal

   The unit is packed, levelled, fixed and flashed so water getting past the face drains back out instead of into the frame. The air seal between the joinery and the framing matters more in a cold climate than most people realise, because that gap is a direct path for heat and for draughts.

7. Reinstate, clean and hand over

   Linings, scotia and architraves go back, glass is cleaned and the site is cleared. Window and Glass Repair Dunedin walks the job with you, hands over the keys and explains exactly what the manufacturer warranty covers and what it does not.

Why Dunedin homeowners choose Window and Glass Repair Dunedin for thermally broken windows

Dunedin is a harder place to fit windows than most New Zealand cities, for reasons that have nothing to do with the windows themselves.

We specify for climate zone 5, not for a national average

The performance figure required here is the highest in the country. Plain aluminium joinery with a standard unit does not reach it, and a quote that assumes it does is either not consented work or is going to fail an inspection. Window and Glass Repair Dunedin tells you which one you are looking at before you commit.

We work on heritage stock every week

Dunedin holds the largest surviving collection of Victorian and Edwardian buildings in New Zealand. Fitting modern joinery into a house built in 1895 is a different job to fitting it into a 1990s subdivision, and the difference is in the reveals, the linings and the proportions.

We allow for frost and condensation properly

Around fifty ground frost days a year means the inside face of the glass and the frame spend a lot of the winter well below room temperature. That is why frame choice matters here in a way it does not in Auckland, and why we raise thermal breaks rather than waiting to be asked.

We put the third party costs at cost

Consent fees and any engineering are shown as their own lines at what they cost us. Bundling them into a per window rate makes two quotes impossible to compare, which is usually the point of bundling them.

What thermally broken windows costs in Dunedin and how long it takes

Joinery is the largest single spend on most window projects, so here are the real numbers and the real timeline rather than a range wide enough to mean nothing.

Per window, fitted

Aluminium runs roughly $550 to $850 per window supplied and fitted on a straightforward like for like replacement. Thermally broken aluminium sits above that. Timber joinery runs about $800 to $1,250 per window, and more where the profile has to be matched to existing heritage joinery rather than ordered from a standard range.

Whole house

A full re joinery on an average Dunedin home typically lands between $10,000 and $24,000. The spread inside that is driven by three things: how many openings there are, whether they are standard sizes or all different, and whether the house is single or double storey, because scaffolding on a two storey villa is a real line rather than a rounding error.

The timeline, honestly

Measure to installed is typically six to ten weeks. Four to six of those are manufacture and nothing can compress them. Site time is usually one to three days for a few openings and a week or more for a full house. Window and Glass Repair Dunedin confirms the manufacturing date in writing before booking the fit.

What sits outside the quote

Repainting the room after linings are disturbed, curtains and blinds being rehung, and consent fees where the work is consented. Window and Glass Repair Dunedin states each of those so they are decisions rather than surprises.

Choosing between the joinery options in Dunedin

In climate zone 5 the frame material decides more about the long term result than the glass does. Here is the honest comparison.

Standard aluminium

The cheapest and the strongest, with the slimmest sightlines. It also conducts heat straight through the frame, which in a city with fifty frost days a year means the frame will be the coldest surface in the room and will sweat even behind good glass. Fine on a sheltered elevation or a garage, poor in a bedroom.

Thermally broken aluminium

An insulating strip separates the inside and outside faces, so the internal frame stays near room temperature. It costs meaningfully more per window and it is the option that actually solves condensation rather than relocating it. On consented work in this climate zone it is effectively the default.

Timber

Warm by nature, and the only option that keeps the proportions and sightlines a Victorian or Edwardian house was designed around. It needs painting on a cycle and it costs more up front. On a character street it is usually worth both, and on a modern house it rarely is.

uPVC

Good thermal performance for less than thermally broken aluminium, with noticeably wider frames and a different look. It suits rental and investment property well, where performance per dollar matters more than sightlines, and it reads wrong on a heritage frontage.

What a thermal break does in a Dunedin window

It is a strip of insulating material inside the frame and it changes the coldest part of the window.

Aluminium conducts, and that is the problem

A standard aluminium frame connects the outside air to the inside face through solid metal. The frame ends up colder than the glass, which is why sweating starts at the edges even on double glazed windows.

The break separates the two faces

A polyamide or resin strip between the inner and outer sections stops the conduction path. The inner face stays close to room temperature and the condensation stops forming on it.

Where it matters most

Bedrooms and living rooms on the cold side of the house, and any room where condensation is already a problem. It matters less on a sheltered elevation with good heating.

Specifying and installing in Dunedin

Thermally broken joinery is a new joinery decision, not a retrofit one.

It cannot be retrofitted to an existing frame

The break is part of the extrusion. Where the frames are staying, retrofit double glazing improves the glass and leaves the frame as it is, and we are clear about that limit.

H1 requirements on new and altered work

The Building Code insulation requirements set minimum performance for windows in new builds and significant alterations, and the required figure varies by climate zone. Standard aluminium with a standard unit does not reach it.

Cost against standard aluminium

Meaningfully more per window, and the gap narrows when you compare it against the cost of solving condensation twice. On a new build it is now the sensible default rather than an upgrade.

Thermally Broken Windows at a glance

How it works

Polyamide strip separates the inner and outer halves of the frame

Fixes

Condensation forming on the aluminium frame itself

Best for

South and west elevations, bedrooms, warmth focused renovations

Cost

Higher per opening than standard double glazed aluminium

Wind rating

Still specified to NZS 4211 for the site climate zone

Glass

Double glazed as standard, Low E and argon available