Double glazing, secondary glazing, or curtains
Cold windows are the thing people most want to fix and the thing most likely to be quoted at a price that stops the conversation. There are three answers, they cost wildly different amounts, and one of them is often enough.
The short answer
Curtains with a pelmet stop warm air rolling down the glass and circulating, and they cost the least by a long way. Secondary glazing adds a second pane inside the existing window, keeps your frames and costs a fraction of replacement. Full double glazing replaces the whole window and frame, performs best, and is by far the most expensive. Do the cheap one first and measure whether it was enough. The rebate on any of them is small next to the price, so this is a finance and comfort decision rather than a rebate one.
Try first
Full length lined curtains with a pelmet or a sealed track, in the coldest room. Cheap, quick, and often more effective than people expect.
The middle option
Secondary glazing keeps your existing windows and frames. It is the option most people have never heard of and it fits most budgets.
Not the reason
The rebate on glazing is a small share of the job. If somebody is selling you windows on the rebate, ask what the price is without it.
What is actually happening
Two problems, and only one of them is heat.
Single glass is a poor barrier. Heat crosses it easily, so on a cold night your window is cold. Warm air in the room touches the glass, cools down and slides to the floor. That is the draught you feel near a window even when nothing is leaking. The room is stirring itself, and it never feels warm no matter how long the heater runs.
The second problem is the frame. Old aluminium frames carry heat away almost as fast as the glass does. A gap around the frame is worse again, because that is a real air leak. Two houses with identical glass can behave completely differently because of what is holding it.
That matters because the three fixes address different parts of it. Curtains deal with the air movement. Secondary glazing deals with the glass. Full replacement deals with the glass and the frame together. Knowing which of the three is your actual problem is what decides whether the cheap answer is enough.
The pelmet part matters
A curtain with an open gap at the top lets the cold air slide out over the rail and into the room anyway. A pelmet, or a track that closes off the top, is what turns a curtain from decoration into insulation.
The three options
Cheapest first, because it is often enough.
Curtains, blinds and a pelmet
Heavy lined curtains that run floor to ceiling and are closed off at the top. Honeycomb blinds do a similar job in a smaller space. The cheapest option on this page by a very long way, and the only one you can do this weekend.
Why it comes here
Stops the air rolling. Does nothing while they are open, which is the honest limit of it.
Who does it
A curtain maker, or yourself. Ask specifically about a pelmet or a sealed track, not just the fabric.
Secondary glazing
A second pane fitted inside the existing window, on its own light frame. Your original windows stay, which matters in a heritage house where you may not be allowed to change them. It performs close to double glazing on the glass, and it costs a fraction of a replacement.
Why it comes here
The middle option almost nobody is offered. Keeps the frames, keeps the look, keeps most of the benefit.
Who does it
A secondary glazing specialist. Not every glazier does it, so ask before you assume it is not available.
Full double glazing
The whole window comes out and a new sealed unit and frame go in. It performs best, it fixes the frame and the leaks at the same time, and it is the most expensive thing on this site. Doing a whole house at once is a renovation sized decision.
Why it comes here
Best result, biggest price. Best value when it rides along with a renovation that has the walls open anyway.
Who does it
A glazier or window company. Ask about the frame material, because that decides half the performance.
Why the rebate is not the story
It is real, and it is small.
Victoria pays a set rate per ten square metres of double glazing. Secondary glazing has a lower rate on paper, but no secondary glazing product is approved for it right now, so it cannot currently be claimed. Work it out per square metre and it comes to around twenty one dollars. A typical house has twenty to thirty square metres of glass.
So on a job that runs into many thousands of dollars, the discount is in the hundreds. It is worth having. It is not worth deciding on, and it is not worth a quote being built around.
This is the one upgrade where we would tell you to ignore the rebate. Think about the money instead. Do the worst rooms first, spread it over a few years, and ask about payment terms. The rebate figures below are the real ones, and they are the reason we say this rather than an argument against them.
Where this comes fromenergy.vic.gov.au, checked 28 October 2026
Doing it a room at a time
Start where the sun does not go.
Almost nobody needs to do a whole house at once. Doing it a room at a time is how most people afford it at all. The order is simple. Start with the coldest room you actually use. That is usually the one facing south, with the most glass and no winter sun.
Then do the rooms you spend the evening in. A cold bedroom at ten at night matters less than a cold lounge at five. You are under a doona in one and sitting still in the other.
Leave the rooms with morning sun until last. They pick up free heat every clear morning and they are the least uncomfortable to be in.
Ask any company that quotes you for a whole house to also price the two worst rooms on their own. A good one will do it without complaint, and the difference between those two numbers is what tells you whether to spread the job out.
What we couldn’t confirm
The window numbers we would not repeat.
Glazing carries a lot of very specific pricing in circulation and almost none of it survives a check.
“About $350 a window, around $3,500 for a house”
This circulates on installer adjacent sites. It contradicts the government’s own figures by a wide margin and we could not trace it to any primary source.
“Double glazing cuts your heating bill in half”
It depends entirely on how much glass you have and what else is insulated. In a house with a poorly insulated ceiling, the windows are not the biggest hole.
A federal window rebate
There is no national program for glazing. State schemes cover it at modest rates, and the ACT loan scheme specifically excludes it.
Quick answers
The questions people ask next.
Does secondary glazing look bad?
Done well, most visitors do not notice it. It sits inside the reveal on a slim frame. It is the standard answer in heritage areas overseas for exactly that reason.
What about the film you stick on the glass?
Window film is mostly about summer heat and glare rather than winter warmth. It is genuinely useful for a hot west facing room. It is not a substitute for a second pane.
Will new windows fix my condensation?
Partly. Warmer glass means less water forming on it, but the water is still in the house and will find the next coldest surface. Read the ventilation guide alongside this one.
uPVC, timber or aluminium?
Thermally broken aluminium and uPVC both perform well. Plain aluminium conducts heat badly and undoes some of what the glass gains. Ask what the frame is, not just what the glass is.
Can I do it in a rental?
Curtains and honeycomb blinds, yes, and they come with you. Secondary glazing sometimes, with the owner’s permission, and it is worth asking because it is removable.
How long does the work take?
Curtains are a day. Secondary glazing is usually a day or two for a house. Full replacement is a week or more and involves the outside of the building, so weather gets a say.
What to do this week
Cheapest test first.
Tonight
In the coldest room, hold your hand near the glass and then near the floor below it. If the floor is colder, air is rolling down and curtains will help.
This week
Work out which two rooms you actually sit in on a winter evening. Those are the ones to quote first.
Before quoting
Ask any window company for a two room price alongside the whole house price. It changes what is affordable.
When you’re ready for help
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