Double glazing the aluminium frames on older Wellington houses
Aluminium double glazing suits old frames that are still sound, but if water gets in around yours in a storm, have the frames checked first. That way you won't pay for new glass in a window that turns out to need replacing. For the rest of the house, read about double glazed windows in older Wellington homes too.
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Water getting in through old aluminium joinery in storms
When old aluminium windows let water in during a storm, the next question is whether to replace them or put new glass in. That's hard to answer until someone has looked at the frames.
NIWA says heavy rain west of the ranges usually comes on a warm, moist north to north-west flow ahead of a front. Keep a note of which windows leak and in what weather, so whoever checks them knows where to look.
If the frames turn out to be sound, look at retrofitting double glazing. If they aren't, it may be time to think about replacing the windows.
What to have checked
- The sills
- The flashings around each window
- The seals around the glass and the openers
Ask for whatever they find to be written into the quote.
NZS 4211, the standard for how windows perform, covers keeping water out as well as strength, stiffness and air infiltration, at the wind pressures of each wind zone.
Openers, fixed panes and how many units you pay for
A Wellington glazing firm's published retrofit prices are per glass unit, which is one pane, or one sealed double glazed unit, rather than a whole window. So an aluminium window with a fixed pane beside an opener counts as at least two.
The same firm says an opening pane costs more than a fixed one.
When you tally up your windows, list the openers and the fixed panes separately, and ask for each to be priced on the quote.
Get the openers and fixed panes pricedSlim 1970s profiles and centre mullions
Wellington owners with 1960s aluminium or 1970s Lockwood joinery ask whether to keep the frames and change the glass, or replace the lot.
If it's replacement, two more questions follow. Will the new frames look bulkier than the slim old profiles? And can a centre mullion come out of a big window without weakening the glass?
Both depend on your frames and on the new ones you're quoted, so raise them at the measure.
Without the mullion the pane gets bigger, and NZS 4223.4 sets the minimum thickness of glass for the wind load it has to take, so ask how the glass for that pane has been worked out. Before you commit to replacing windows in a Wellington house, see the new frame profile for yourself and check which wind zone each window will be labelled for.
It's worth saying in your enquiry which windows leak in a storm, and whether there's a mullion you'd like gone.
Ask for a quoteSeals and hardware on the openers
Draughts around an aluminium opener get in through the gaps, not the glass. Ask whether the quote for retrofitting your windows with double glazing includes new seals and any hardware the openers need.
On MBIE's H1 table, a window with standard double glazing gets R0.24 if the aluminium frame is standard and R0.30 if it's thermally broken, and double glazed windows can still get condensation on a standard frame.
Pricing each glass unit in an aluminium window
For new glass in aluminium frames, the prices a Wellington glazing firm publishes run $550–850 per glass unit, incl GST, as at February 2026.
How much is that for one window? A window with two glass units, say a fixed pane beside an opener, comes to $1,100–1,700 incl GST on those prices. That's our own arithmetic, not a figure the firm publishes.
Each extra pane adds another unit. For the firm's other prices and national figures for a whole house, see what a double glazing price is made up of.
Ask what your windows would come toPublished by a Wellington glazing firm, February 2026
New glass in aluminium frames
$550–850
per glass unit, incl GST
Our arithmetic from that price
A fixed pane beside an opener
$1,100–1,700
per opening with two glass units, incl GST
We re-checked the firm's list on 17 September 2026.
What owners of older aluminium frames ask
Can old aluminium windows be double glazed?
Yes, provided the frames are in good order, since the new glass goes into the aluminium you already have. Have any frame that leaks looked at before the glass is ordered.
Is aluminium double glazing any good?
For the glass itself, yes. The seals and the frame only change if the quote covers them, so check what's included before you compare prices.
Is uPVC better than aluminium?
With the same glass, uPVC rates higher than either kind of aluminium on MBIE's R-value table, but it means a whole new window, not new glass in the frames you have.
How do I tell whether my aluminium frames are thermally broken?
Ask whoever measures up to look and tell you. It matters when you're weighing new glass against new windows, because new aluminium windows come standard or thermally broken, while new glass leaves yours as they are.
Get the frames checked and the glass priced
Tell us roughly how many aluminium windows you have and whether any of them leak, and we'll send that to a local installer with your contact details.