The question comes up constantly: should I retrofit double glazing into my existing frames, or should I replace the windows entirely?
For most Melbourne homes, the answer is clear. Here is the honest comparison.
Cost
Retrofit into existing frames: $495–$850/m² installed, depending on glass specification.
Full window replacement: $900–$1,500/m² installed for standard aluminium replacement windows; $1,400–$2,200/m² for timber.
A whole-home retrofit typically costs $8,000–$14,000. The same job in full replacement windows: $18,000–$35,000.
The glass specification inside a replacement window is identical to what you can achieve with retrofit. You are paying the difference for new frames, new seals, new hardware, and the labour to remove and re-install in the opening.
Thermal Performance
Thermal performance is determined by the glass unit — specifically the U-value of the IGU and any coatings applied. The frame material contributes, but the glass dominates.
A retrofit IGU with soft-coat Low-E and argon fill achieves U-value 1.4–1.6 W/m²K. A replacement aluminium window with the same IGU spec achieves the same — possibly marginally better if the frame has a true thermal break.
For practical purposes: the thermal performance is equivalent.
Disruption
Retrofit: Glass is removed and replaced within the existing frame. Most windows take 20–40 minutes. A whole-home retrofit is typically a one-day job with no structural work, no plaster repairs, and no painting.
Full replacement: Frames are cut out of the opening, new frames installed, gaps filled, revealed patched, painted. A significant renovation job — typically 3–5 days and subsequent plastering and painting work.
Appearance
Retrofit: The exterior of the building is unchanged. Frame colour, profile, hardware — all identical to before. Ideal for heritage homes, strata buildings with common-area approval requirements, or owners who prefer not to change the home's character.
Full replacement: You get new frames, which is a visual change. Some owners want this; many do not.
When Full Replacement Makes Sense
There are cases where full replacement is the right call:
- Structurally compromised frames: Significant timber rot, cracked aluminium extrusions, failed corner joints that cannot be repaired.
- Rebate too shallow: Some very old or non-standard frames genuinely cannot accommodate a 20mm+ IGU without major modification — at which point replacement may be simpler.
- Whole window upgrade: You want to change from single-hung to double-hung, casement to awning, or add a new window where none exists.
If your frames are structurally sound — which most Melbourne homes' frames are — retrofit wins on every financial and practical measure.
Getting a Quote for Both
The Retrofit Double Glazing page covers the retrofit process in full. The Instant Estimate tool gives you a retrofit price for your specific windows.
For full replacement pricing, contact us directly — it requires a site measure.
Related: Is retrofit double glazing worth it?
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