Aluminium double glazing for existing Christchurch windows
Aluminium double glazing is usually a retrofit: the single pane comes out of your existing aluminium frame and a sealed unit goes in. Whether your frames can take it depends more on their profile than their age. If you're still weighing up new windows, Double glazed windows in Christchurch compares the two.
Get a quoteCan your aluminium windows take double glazing?
Three things decide it. The rebate, the channel the glass sits in, has to be deep enough for a unit that is two panes and a gap thick instead of one pane. The frame has to be straight, because a sealed unit won't forgive a twisted sash the way a single pane does. And the drainage holes in the bottom rail have to be clear, or the unit sits in water.
Where the rebate is shallow, installers use an adaptor or a new bead that adds depth to the frame, and the industry guide for insert windows covers a second option: a new sash or insert fitted into the existing outer frame. If even that won't work, you'll need a new window. The installer should tell you which of the three applies when they measure, before you pay a deposit.
On Christchurch forums, people argue less about whether it can be done and more about whether it's worth doing in a standard aluminium frame at all.
Is double glazing worth it in a standard aluminium frame?
Usually, yes. A standard aluminium frame is one piece of metal from outside to inside, so it stays cold, but most of a window's area is glass, and the glass is where retrofit makes the difference. The Building Code's reference figures put single glazing at about R0.19 and a retrofit with low-E and argon in a standard aluminium frame at R0.35. That's a big improvement for the money.
What retrofit won't change is the frame itself. If a cold, wet frame is the main thing you want gone, or the frames are failing anyway, new joinery with a thermal break is the better job, at several times the cost of a retrofit. The thermally broken aluminium windows page explains that route.
Why aluminium frames still run with condensation
Double glazing keeps the glass warm. It does nothing for a standard aluminium frame, which stays as cold as the air outside, so on a frosty morning the frame can still be wet while the glass is dry. Consumer NZ notes that thermally broken frames help with this, and EECA favours uPVC or timber for replacement frames partly for the same reason.
If wet frames are your main complaint, a retrofit will help a lot but won't fix them completely. The rest is ventilation and heating habits, which the how to stop condensation on windows guide covers, and if that's not enough, new frames are the answer.
Ranch sliders and aluminium doors
Mention these separately, because they can change the price a lot. Glass in a door or a side panel has to be safety glass under NZS 4223.3, so the units are laminated or toughened, heavier and dearer than a window pane. Whether an existing slider can be retrofitted depends on its sash and track in the same way a window depends on its rebate.
Replacing a slider outright is priced like several windows. Published figures for a new aluminium sliding door run from about $2,500 to $5,000 at the low end to $6,000 to $12,000 from installers quoting the larger sizes, so it is worth deciding early whether the doors are in the job or not.
Not sure whether your profile will take a unit?
Tell us the rough age of the joinery and how many windows, and the installer can say what's likely before anyone visits.
What aluminium retrofit costs in Christchurch
About $400 to $900 per pane, or $10,000 to $18,000 for a typical three-bedroom house in aluminium frames. Published NZ installer pricing, 2026, including GST. The price is per pane, so a window with one fixed pane and one that opens counts as two. For what pushes the price up or down, see how much double glazing costs in Christchurch. The retrofit double glazing page explains how the job is done.
- Retrofit, aluminium frames~$400–900 / pane
- 3-bedroom retrofit, aluminium$10,000–18,000
- New thermally broken window~$2,000–3,500
Published NZ installer pricing, 2026, incl GST
Aluminium double glazing FAQ
Can aluminium windows be double glazed?
Most can, if the frame is straight, the rebate is deep enough to hold a sealed unit, and the drainage still works. The installer checks that at the measure. Some older, slim profiles have no room for a unit at all, and those windows are replaced rather than retrofitted.
How much does a double glazed aluminium window cost?
Retrofitting a sealed unit into an existing aluminium frame is about $400 to $900 per pane. A new standard aluminium window is roughly $1,200 to $2,500 installed, and a thermally broken one $2,000 to $3,500. Published NZ installer pricing, 2026, including GST. The double glazing cost guide has the whole-house figures.
Can aluminium sliding doors be double glazed?
Often, the same way a window can: it depends on whether the sash and track have room for a thicker, heavier unit. Door glass has to be safety glass under NZS 4223.3, so the units are laminated or toughened and cost more than a window pane. If the slider needs replacing anyway, published figures for a new aluminium sliding door start around $2,500 to $5,000.
My aluminium joinery is from the 1980s. Can it still be retrofitted?
Often, yes. Age matters less than profile depth and condition. Christchurch homeowners asking this online have had both answers, because some 1980s profiles take a unit and some don't. Ask the installer to check the rebate on a couple of windows before quoting, and to say plainly if replacement is the better job.
Get your aluminium windows measured
A local installer will measure up and price each pane separately.