Published · Clear Vision Glass & Glazing
If your house is cold in July, noisy from the highway, or streaming with condensation every winter morning, you will get quotes for three quite different things — and they will all be described as double glazing. They are not the same, and the gap between the cheapest and the most expensive is very large.
Option one: retrofit an insulated glass unit
A sealed double glazed unit — two panes with a spacer and a gas-filled cavity — installed into your existing window frame. The frame, the architraves, the render and the paintwork are all left alone.
This is the best value option by a wide margin when it is possible. It delivers the real thermal and acoustic benefit of double glazing at a fraction of the cost of new windows, and it is a day's work rather than a renovation.
The catch is that not every frame can take it. The glazing rebate has to be deep enough for the unit thickness, and the frame has to be sound and square. Many older shallow aluminium sections genuinely cannot accept a sealed unit, and no amount of enthusiasm changes that. This is why we assess before promising it.
Option two: secondary glazing
A second pane or panel added on the inside of the existing window, with an air gap between them. It is common in heritage properties where the original windows cannot be altered.
It performs surprisingly well acoustically — often better than standard double glazing for low-frequency traffic noise, because the air gap is much larger. Thermally it is decent but not equal to a proper sealed unit, because the cavity is not sealed or gas-filled.
The trade-offs are practical. It is another surface to clean, it changes how the window opens, and it can look like what it is. Where the original windows must be preserved, it is often the only sensible answer.
Option three: full window replacement
New frames and new double glazed units together. The best performance available, because you also fix the frame — thermally broken aluminium or uPVC frames, proper seals throughout, and no compromises from working around existing joinery.
It is also by far the most expensive and the most disruptive, involving render, architraves, paint and sometimes flashing. It makes clear sense when the existing frames are genuinely failed — corroded aluminium, badly rotted timber, or windows that are out of square — or when you are already renovating that part of the house.
It rarely makes sense purely as an efficiency upgrade if the existing frames are sound. The extra performance over a retrofit unit does not usually justify the extra cost and mess on its own.
Do the cheap things first
Before any of the above, deal with the gaps. Perished weather seals, worn brush strips and failed gaskets let in wind, dust and noise, and replacing them across a whole house costs a small fraction of any glazing upgrade.
This matters more than people expect for noise. Sound travels through gaps very effectively, and an expensive acoustic glazing upgrade in a window with failed seals will underdeliver badly. Fix the seals first, then decide whether you still need the glass.
Do it room by room
Whole-house double glazing is a significant spend and there is no rule saying it has to happen at once. The sensible order is to start where the problem actually is — usually the west-facing living areas that overheat from three o'clock onward, and the bedrooms facing the road.
Specify by elevation rather than uniformly. Low-E coatings earn their cost on west and north-facing glass and do comparatively little on south-facing windows. Acoustic laminated makes sense on the road side and is wasted on the back of the house. Applying the same premium specification everywhere is how a quote gets to a number nobody proceeds with.
Want this looked at?
We’re glaziers based in Pakenham servicing Cardinia Shire and the City of Casey. Free quotes, and for most jobs a photo is enough to get a price.
