The short answer
A Melbourne window company prices installed secondary glazing at $1,800 to $3,400 per window↗ and full double glazed replacement at $2,300 to $3,500 per window↗. Per square metre the gap is much wider: $300 to $650 per m²↗ against $1,200 to $1,800 per m²↗. Secondary glazing changes the glass layer only↗, so tired frames and failed seals stay where they are.
How do the prices compare?
Installed price per window
Show the numbers
| Item | Range |
|---|---|
| Secondary glazing | $1,800 to $3,400 |
| Double glazed replacement | $2,300 to $3,500 |
Per window the two ranges overlap almost completely, which surprises people who expect secondary glazing to be the budget option. The source notes that fixed windows sit at the bottom of the secondary range and tilt and turn units at the top, so the style you have drives the number.
Installed price per square metre
Show the numbers
| Item | Range |
|---|---|
| Secondary glazing | $300 to $650 |
| Double glazed replacement | $1,200 to $1,800 |
By area the picture flips, and secondary glazing looks far cheaper. Both sets come from the same company, so the difference is not a quirk of two price lists. It is a reminder to price your own job both ways before deciding which comparison you believe.
What does secondary glazing leave alone?
The window. Secondary glazing adds a pane in its own slim frame inside the opening, so it upgrades the glass layer only↗. If the existing 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.
| Question | Secondary glazing | Replacement |
|---|---|---|
| Installed price, per window | $1,800 to $3,400 per window↗ | $2,300 to $3,500 per window↗ |
| Installed price, per m² | $300 to $650 per m²↗ | $1,200 to $1,800 per m²↗ |
| Fixes frames and seals | No, it is the glass layer only↗ | Yes, the frame is new |
| Keeps the original window | Yes | No |
When does each one make sense?
If the frames are sound and you want to keep them, for looks or for a heritage overlay, secondary glazing gets a second pane in without touching the original joinery. If the frames are the problem, spending money around them only postpones the job. Draughts are worth a thought here too: sealing gaps is a separate, much cheaper piece of work, 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 for a sales brochure. Ask the provider to name the product and show you where it is listed.
Is replacement a bigger job on paper?
It can be. Victoria's building regulator treats full replacement of building elements as 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 insurance thresholds that come with it.