Where this lands
Secondary glazing is the cheaper option upfront. How much cheaper depends on who you ask: a Melbourne company that sells replacement windows says it is around 30% cheaper upfront, while a Perth company puts it at roughly 40 per cent of the cost of full double glazing. Neither publishes an installed dollar price for it. Full replacement in Melbourne runs $2,300 to $3,500 per window. What the lower price buys is an upgrade to the glass layer only, so worn frames and failed seals stay behind the new pane.
Correction, 16 September 2026: an earlier version of this page listed a replacement window price as the price of secondary glazing, and concluded the two cost about the same. That was wrong. The figures below replace it.
Why is there no installed price for secondary glazing here?
Because we couldn't find one we can link to and stand behind. The Melbourne company whose replacement prices we use says secondary glazing prices vary widely by supplier and panel type, and leaves it there. What it does publish is the DIY end of the market: basic acrylic kits at $150 to $300 per window, and branded magnetic systems at $300 to $500 per m², supply-only. Neither of those includes anyone coming out to fit it.
So if you want a real number for professionally installed secondary glazing, the sensible route is the one the source suggests: ask two or three secondary glazing specialists to quote the same windows.
What does each way of upgrading a window cost?
Three ways to upgrade a single glazed window, per window
Show the numbers
| Item | Range |
|---|---|
| DIY acrylic secondary glazing kit | $150 to $300 |
| New glass units in old aluminium frames, Perth | $800 to $1,800 |
| Full double glazed replacement, Melbourne | $2,300 to $3,500 |
The middle bar is an option people often miss. If your existing frames are aluminium and in sound condition, a Perth company quotes $800 to $1,800 per window to fit new double glazed units into them. That only works where the frame is deep enough to take the thicker glass, so it's a question for a glazier who has seen the window.
How much performance do you give up?
Reported U-values, lower is better
Show the numbers
| Item | Range |
|---|---|
| Single glazing plus a secondary pane | 3.0 W/m²K |
| uPVC double glazed replacement | 1.6 to 1.7 W/m²K |
On the Melbourne company's own figures, single glazing with a secondary acrylic pane reaches a U-value of about 3.0, against 1.6 to 1.7 for a uPVC double glazed replacement. That is a real step up from bare single glazing, and still well short of a new window. Keep in mind who is telling you: this is a replacement seller describing the cheaper alternative.
The Australian Government's YourHome guide, which sells nothing, lands in the same place. It says an added pane cuts heat loss and draughts but performs less well than a manufactured double glazed unit, because the edges of a retrofitted pane can't be fully sealed. It also notes secondary glazing can give good noise control.
What does secondary glazing leave alone?
The window itself. The added pane sits in its own slim frame inside the opening, so everything behind it is untouched. If the sashes stick, the timber is soft at the sill or the seals have gone, all of that is still there afterwards, now behind a second layer.
When does each one make sense?
- Heritage homes and short stays. The Melbourne company lists secondary glazing as reversible, with no external change, which is why it suits a heritage overlay or a home you'll leave in a few years.
- Sound frames, cold rooms. If the frames are in good order and the glass is the weak point, secondary glazing is the cheaper way to add a second layer of glass.
- Frames that are the problem. Spending money around a rotten or rattling frame only postpones the job. Price replacement.
- Draughts. Sealing gaps is a separate and much smaller job, and Victoria has a discount of up to $700 for weather sealing products.
Does the Victorian discount apply to secondary glazing?
The window glazing discount is written around double glazing and requires approved products only. Whether a particular secondary glazing product is on the register is a question for the register itself, not a sales brochure. Ask the provider to name the product and show you where it's listed.
Is replacement a bigger job on paper?
It can be. Victoria's building regulator says full replacement of building elements is treated as an alteration, so a registered building surveyor is the right person to ask before a large job starts. Our quote guide covers the contract and Home Warranty rules that can come with it.