Retrofit Double Glazing in Dunedin – Existing Frames Retrofitted with Sealed Units
Window and Glass Repair Dunedin retrofits double glazing into existing timber and aluminium joinery right across the city. Instead of pulling your windows out, we machine the rebate or fit a new bead, drop a sealed unit into the frame you already have, and reseal it. The window looks the same from the street and the room stops being cold.
- Keeps your existing frames, so villas keep their character
- Roughly half the cost of full joinery replacement
- Most Dunedin projects land between $10,000 and $24,000
- Exempt from building consent as like for like work
Get your free quote
Four quick questions. Most quotes come back the same day.
No New Zealand city suits this better. Dunedin holds the largest concentration of Victorian and Edwardian buildings in the country, a legacy of the 1861 gold rush, and the residential stock that came with it is timber sash on a scale nowhere else can match. Owners here do not want aluminium in a villa opening, and they are right. Retrofitting costs roughly half of full replacement and the disruption is measured in days.
What it costs in Dunedin
Cost guides put most Dunedin retrofit projects between $10,000 and $24,000, with the wider band running from about $4,000 for a small job up to well over $50,000 on a large character home. Per square metre of glass, retrofit models at roughly $450 to $800 against $800 to $1,600 for full replacement.
Two things push Dunedin quotes around. Hill suburbs add access and handling. And the colder climate zone lifts the glass spec, because Low E is the sensible default here rather than an optional extra. Low E typically adds around a third to the glass price.
Timber frames get checked before anything is ordered
A retrofit only works if the frame is sound and deep enough to carry the unit. On timber we probe the sill and the bottom rail first. Soft timber there has to be repaired before glass goes near it, otherwise you have put a twenty five year unit into a frame with five years left in it.
We quote the timber work and the glazing together so nothing appears halfway through. On a whole house lot we usually take the sashes back to the bench, do the repairs, glaze, repaint and refit, which gives a far better finish than working in place.
Getting the glass right for a cold city
The standard build is 4mm glass, a 12mm gap and 4mm glass. In Dunedin we would almost always put Low E on that, because the coating reflects radiant heat back into the room and the payback in a fifty frost day climate is real. Argon fill improves it again.
Laminated on the outer pane cuts noise, which matters on the arterial routes and around the student quarter. And in doors, wet areas and low level positions the glass has to be toughened or laminated under NZS 4223 whatever was there before.
Consent, and what the rules say
Retrofitting glass into existing frames on an existing home is like for like work, exempt under Schedule 1 of the Building Act. No consent, no council fees.
That changes if the opening is enlarged, structure is altered, or the work forms part of a larger consented renovation. Consented residential work has to meet R0.50 here, which a retrofit into a plain aluminium frame will not reach, so the two paths are worth keeping separate in your head.
How Window and Glass Repair Dunedin delivers retrofit double glazing in Dunedin
Dunedin is the hardest thermal environment in the country for windows, and it is the one place where the wrong specification is genuinely expensive over time.
Assess the room, not just the window
How the room is heated, ventilated and used decides as much about the outcome as the glass does. Upgrading glazing in an unventilated bedroom moves the condensation to the frame edges rather than removing it.
Establish the requirement that applies
Dunedin is H1 climate zone 5, the highest window performance requirement in New Zealand. Window and Glass Repair Dunedin confirms whether your work is consented and therefore has to meet it, or a like for like replacement that does not, because the two lead to very different products.
Measure and record what exists
Opening sizes, room floor areas, existing glass type and frame construction. On compliance work that record is the evidence behind the statement you make to a tenant or to council.
Specify the unit deliberately
Glass thickness, cavity width, low emissivity coating, argon fill and spacer type all get chosen for the orientation and the exposure rather than sold as a package. Window and Glass Repair Dunedin explains what each component does.
Be honest about the frame
Retrofitting a sealed unit into a standard aluminium frame improves the glass and leaves the frame conducting. In a city with fifty frost days a year that frame will still sweat, and Window and Glass Repair Dunedin says so before quoting rather than after.
Manufacture and install
Units are made to the measured openings, so there is a lead time and nothing is adjusted on the day. Installation includes new tape, new beads and clearing the rebate drainage.
Verify, document and hand over
Every sash checked to operate and to fix open, then a written record of what was installed where. On a rental that document is what supports compliance if it is ever questioned.
What retrofit double glazing is worth in a Dunedin home
The case here is stronger than anywhere else in the country and the numbers are worth knowing.
The highest requirement zone in New Zealand
Climate zone 5 carries the country's highest window performance requirement because heat loss here is greater. A specification that satisfies a warmer city does not satisfy this one, which is why comparing a Dunedin quote to a friend's Auckland quote is misleading.
Retrofit is usually the best value route
Around $450 to $800 per square metre of glass, or roughly $550 to $850 per aluminium window and $800 to $1,250 for timber. A whole house commonly lands between $10,000 and $24,000, and the existing frames and finish stay.
Do the rooms you use, first
Bedrooms and living areas on the cold elevation return most of the benefit. Small hallway and toilet windows return the least and are worth doing last, or not at all.
Cold housing is under real scrutiny here
MBIE inspected fifty three Dunedin student rentals across May and June 2026. Whatever your view of the rules, the direction is clear, and upgrading ahead of enforcement is cheaper than upgrading during it.
What retrofit double glazing costs in Dunedin
Thermal work here has a stronger case than anywhere else in New Zealand, and the numbers are worth seeing before the sales pitch.
Retrofit double glazing
Roughly $450 to $800 per square metre of glass, or about $550 to $850 per aluminium window and $800 to $1,250 for timber. A whole house commonly lands between $10,000 and $24,000 with the existing frames and internal finishes untouched.
Sealed unit upgrades
A low emissivity coating, an argon fill and a warm edge spacer add very little to a unit being made anyway. In climate zone 5 they are close to free performance, and retrofitting them later means paying for the unit twice.
New thermally broken joinery
Meaningfully more per window than standard aluminium and it is the only route that removes the cold bridge through the frame entirely. On consented work in this zone it is effectively the requirement rather than an upgrade.
Compliance work on a rental
Most Healthy Homes ventilation failures are hardware rather than glazing. Freeing painted shut sashes, replacing seized stays and fitting working catches usually brings a house into compliance for a fraction of what owners expect.
Where to spend it in a Dunedin home
The same budget produces very different outcomes depending on where it goes.
Bedrooms and living rooms on the cold elevation
These return most of the comfort benefit and most of the condensation reduction. Small hallway and toilet windows return the least and are worth doing last or not at all.
Extraction before glazing, every time
A vented range hood and a ducted bathroom extractor remove moisture where it is produced. This is the cheapest intervention available and it is frequently the only one needed. Upgrading glazing in an unventilated house moves the condensation rather than removing it.
The frame is the limit on a retrofit
Retrofitting a sealed unit into a standard aluminium frame improves the glass and leaves the frame conducting. With fifty frost days a year that frame will still sweat at the edges, and anyone who does not tell you this before quoting is selling rather than advising.
Stage it by room, not by elevation
Doing the rooms people actually use gets you most of the benefit for part of the spend. Doing it by elevation looks tidier from the street and delivers less.
How retrofit double glazing works in a Dunedin house
Retrofit keeps your existing frames and changes what is in them. That is the whole idea and it is also its limit.
The frame has to be sound and deep enough
The rebate has to take a sealed unit, which is thicker than a single pane. On aluminium that usually means a new bead or a converted section. On timber it means routing the rebate deeper, and on rotten timber it means repair first.
Sealed units are made to order
Each unit is manufactured to the measured opening, so there is a lead time and there is no adjusting on the day. Every opening gets measured individually for the same reason as new joinery.
What you get and what you do not
You get a large reduction in heat loss through the glass and a real reduction in condensation on the pane. You do not get a thermally broken frame, so an aluminium frame will still conduct and can still sweat at the edges.
That is the honest limit of retrofit and it is why we explain it before quoting rather than after you notice it.
Retrofit costs and performance in Dunedin
This is usually the best value thermal improvement available on an existing house.
What it costs
Around $450 to $800 per square metre of glass, or roughly $550 to $850 per aluminium window and $800 to $1,250 per timber one. A whole house commonly lands between $10,000 and $24,000.
Where it pays back fastest
Rooms with large single glazed areas facing the weather, and bedrooms where condensation and cold are most noticeable. Small windows in hallways return the least and are worth doing last.
Low E and argon
A low emissivity coating and an argon fill improve the performance of the same unit for a modest addition to the price. On a retrofit, where the frame is already the weak point, it is usually worth specifying.
Retrofit Double Glazing at a glance
- Typical Dunedin project
- $10,000 to $24,000 for a whole house
- Wider range
- About $4,000 at the small end, past $50,000 on large character homes
- Per square metre
- Retrofit around $450 to $800, full replacement $800 to $1,600
- Standard unit
- 4mm glass, 12mm gap, 4mm glass, Low E strongly recommended here
- Low E
- Adds roughly a third to the glass price
- Lead time
- Four to five weeks from measure to completion
- Consent
- Exempt as like for like work under Schedule 1
Retrofit Double Glazing in Dunedin: common questions
Is retrofit double glazing worth it in Dunedin?
In a city with about 50 ground frost days a year, yes. It gets you most of the thermal benefit of new joinery for roughly half the cost and keeps your frames.
Will it work on my villa's sash windows?
Usually. The rebate is machined deeper or a new bead is fitted, and the sash balance is adjusted for the extra weight. We check the timber first.
How long does a whole house take?
Four to five weeks from measure to completion is normal in Otago, with the time on site measured in days rather than weeks.
Does retrofitting get me to the R0.50 code minimum?
Not in a plain aluminium frame, no. R0.50 applies to consented work and needs a thermally broken, uPVC or timber frame. Retrofitting an existing home is exempt work, so the requirement does not apply, but it is worth knowing the difference.
Recent Dunedin jobs
Got three quotes for retrofitting the front of the house. Only ones who measured every opening and explained why the south facing rooms needed different glass. Fourteen windows over three days and the difference in the mornings is obvious.
Landlord here. Had four flats assessed before the inspections. Two just needed sashes freed up and stays replaced rather than new joinery, which saved me a fortune. Straight answers and a written report I could hand over.
Slider had been jamming for years and we assumed it needed replacing. Turned out to be rollers and a bent track. Two hours, a fraction of the price we were braced for.
Fogged unit in the lounge, measured on the Tuesday and in by the following Monday. Fair price and they cleaned up after themselves.
Get a price for retrofit double glazing in Dunedin
Free measure, fixed written quote, and a straight answer on whether it needs repairing or replacing.
Start your quote
Four questions and you are done.