Retrofit Double Glazing: Is It Worth It for Your Sydney Home?
Retrofit double glazing is worth it if your frames are sound and you only need to fix a room or two. It’s less compelling if your frames are aluminium, warped, or near the end of their life.
We don’t sell retrofit double glazing or secondary glazing at Integra Windows. But we will always tell you the right option for your home.
Retrofit Double Glazing vs Secondary Glazing: Two Different Things
Retrofit double glazing means removing the single pane from your existing frame and fitting a sealed double-glazed unit in its place. The frame stays exactly where it is; only the glass changes. It’s an easier way to double-glaze existing windows without a full replacement, if the frame has the depth to accommodate it.
Secondary glazing is a different product entirely. Instead of touching the glass in your existing window, you add a separate acrylic or glass panel inside the frame, usually secured with a magnetic strip. The original window doesn’t change; you’ve just created a second air gap behind it.
For more on what that gap does, see our page on how double glazing works.
What Your Frame Type Allows
- Timber frames suit retrofit double glazing best, since they’re usually thick enough to be rebated out for a slimline double-glazed unit.
- Aluminium frames are often too narrow for a retrofit unit, and because aluminium conducts heat regardless of the glass inside it, the thermal gain is often underwhelming.
- Steel frames rarely work for retrofit. Sightlines are too slim, and modifying them often costs more than replacing the window outright.
For a broader frame comparison, see uPVC windows vs wood vs aluminium, which covers long-term performance, not just installation cost.
What Can Go Wrong With Retrofit Double Glazing
Retrofit double glazing comes with a few risks. Rebating a timber sash to fit a double-glazed unit removes material from the frame. Done well, the sash stays sound. Done on a frame that’s already thin, damp, or partly decayed, it can trap moisture and weaken the sash rather than fix it.
The other issue is lifespan. Some retrofit glazing units come with warranties of around 10 years, but that warranty does not reset the age of the frame around them. A full replacement window includes a new frame and glazing system, while retrofit performance still depends on the condition and remaining life of the existing sash.
Retrofit Double Glazing Cost in Sydney
- Retrofit double glazing cost typically runs $700 to $1,400 per window, assuming the frame needs no repair.
- Secondary glazing Sydney installations, using a professionally fitted magnetic acrylic panel, run $350 to $700 per window.
- Full uPVC replacement costs more, typically $900 to $1,800 per window installed, depending on size and glazing spec.
These are indicative prices. It’s worth getting quotes for all types rather than assuming retrofit is automatically cheaper.
Retrofit vs Secondary Glazing vs Full Replacement
| Retrofit Double Glazing | Secondary Glazing | Full uPVC Replacement | |
|---|---|---|---|
| Indicative cost | $700–$1,400 per window | $350–$700 per window | $900–$1,800 per window |
| Noise reduction | Moderate | Moderate to good | Best |
| Thermal performance | Good, limited by frame material | Moderate | Best |
| Lifespan | 10–20 years, frame dependent | 15–20 years | 25–30+ years |
| Heritage suitability | Good for sound timber sashes | Good, fully reversible | Requires like-for-like approval |
Our guide to uPVC double-glazed windows cost breaks the full replacement figure down further,
and our cost to replace windows in Sydney piece covers renovation-specific factors like access
and heritage approval.
When Retrofit Double Glazing or Secondary Glazing Makes Sense
Retrofit double glazing is a good choice when the frame is timber, structurally sound, and you're only treating a handful of windows. Secondary glazing is the better option for heritage properties where the council won't approve any change to the sash, or in rentals where you can't touch the window at all.
Full replacement is the best way forward when the frame itself is draughty, swollen, rotting, or aluminium with no thermal break. It also gives you more control over whole-window thermal performance when glazing forms part of a BASIX or NatHERS upgrade, because the frame and glass can be specified as a single system.
Our when to replace your windows checklist covers the signs that replacement is the better call.
Integra Windows Expertise
We don’t install retrofit double glazing or secondary glazing. We design, manufacture, and install full uPVC double-glazed windows on the Integra70 frame system in Sydney.
Our profiles are German-engineered and Australian-made, backed by a 10-year warranty and a 30-plus year service life. The improved insulation can reduce reliance on heating and cooling and lower ongoing energy use.
If your frames are past saving, or you want the best result a window can deliver, we can help. For noise-driven upgrades, we recommend our soundproof windows in Sydney. And if you’re comparing options for double-glazed windows more broadly, we’re happy to talk you through where retrofit ends and replacement begins, even if that means pointing you elsewhere.
Retrofit Double Glazing: FAQs
Is retrofit double glazing worth it?
Yes, for the right house. If your frames are timber and sound, retrofit double glazing can lift comfort and noise levels for less than full replacement costs. If they're old, aluminium, or failing, replace them instead.
How much does retrofit double glazing cost in Sydney?
Most jobs land between $700 and $1,400 per window, depending on frame condition, size, and glazing spec. Get a written quote before committing.
What's the difference between retrofit double glazing and secondary glazing?
Retrofit double glazing replaces the glass inside your existing frame. Secondary glazing adds a separate panel in front of the window without touching the original glass or frame.
Can I retrofit double glazing into aluminium windows?
Sometimes, but it's less common. Aluminium sightlines are often too narrow, and since the frame conducts heat, the improvement is smaller than a timber retrofit or full uPVC replacement.
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