Double Glazed Windows: Cost, Benefits & Is It Worth It?

You can have the best heater in the street, but if the warmth is leaking straight out through thin glass, you're paying to heat the backyard. Windows are one of the weakest parts of most Australian homes when it comes to keeping heat in or out. That's where double glazed windows come in.

Double glazing has been standard in cold countries for decades, and it's quickly becoming popular here too, especially in Melbourne, Canberra, Hobart and the Adelaide Hills. But it isn't cheap, so it's fair to ask whether it's really worth the money. This guide explains how it works, what it costs in 2026, the cheaper alternatives and how to decide if it's right for your home.

What is double glazing?

A double glazed window has two panes of glass instead of one, separated by a sealed gap. That gap is usually around 12mm wide and filled with dry air or a heavier gas such as argon. A spacer bar runs around the edge and holds a moisture absorber so the glass doesn't fog up inside.

The trapped layer of air or gas is the clever bit. Heat travels through it far more slowly than through solid glass, so the window acts more like an insulating blanket than a cold sheet of glass.

You might also hear the term IGU, short for insulated glass unit. That's the sealed glass sandwich itself, which sits inside the window frame.

Why windows matter so much

According to the Australian Government's YourHome guide, windows can lose up to 40% of a home's heating energy in winter and let in up to 87% of its heat in summer. That's a huge share coming through a relatively small part of the house.

Ordinary single glazing in an aluminium frame is one of the worst performers. Swapping to double glazing in an insulating frame can roughly halve the heat that escapes through your windows. In practice, that means rooms near the windows feel warmer, the heater cycles off sooner and your energy bill drops.

The benefits of double glazed windows

• Warmer in winter. Less heat escapes, and you lose that icy draught feeling near the glass.
• Cooler in summer. Especially with tinted or low-E glass that reflects some of the sun's heat.
• Lower energy bills. Your heating and cooling don't need to work as hard.
• Less condensation. The inner pane stays warmer, so you get fewer wet windowsills and less mould on cold mornings.
• Quieter home. Double glazing noticeably reduces traffic, neighbour and aircraft noise.
• Better security. Two panes are harder to break than one.
• Higher resale appeal. Buyers in cooler climates increasingly look for it.

How much do double glazed windows cost in 2026?

Costs vary a lot depending on window size, frame type, glass options and how many windows you're doing. As a rough guide:

Option	Typical price
Retrofit double glazing into existing frames (per window)	$400 to $1,200
New double glazed window, installed (per window)	About $600 to $2,000+
Replacing a failed double glazed unit (per window)	$300 to $1,200
Whole home double glazing	$8,000 to $40,000+ (often around $18,000)

Bigger windows, sliding doors, timber frames, argon gas and low-E coatings all push the price up. Getting several windows done at once usually works out cheaper per window than doing them one at a time.

Your options: new windows, retrofit or secondary glazing

1. Full window replacement

Out with the old frame and glass, in with a complete new double glazed window. This gives the best performance, especially if you choose a uPVC or timber frame, which insulates far better than standard aluminium. It's also the most expensive option and is often done during renovations.

2. Retrofit double glazing

Your existing frames stay, but the single pane is swapped for a double glazed unit. It's cheaper and less disruptive, but only works if your frames are in good condition and deep enough to hold the thicker glass. Aluminium frames still let some heat through, so results won't match a full replacement.

3. Secondary glazing

A second pane of glass or clear acrylic is fitted inside your existing window, creating an insulating air gap. It's usually the most budget-friendly option, keeps the original look of heritage windows and is popular with renters and owners of older homes. It's less neat than true double glazing, but it can make a real difference.

Frame matters as much as glass

The frame is a big part of the window, and a poor frame can undo the benefit of good glass.

• Standard aluminium: Strong, slim and affordable, but metal conducts heat easily.
• Thermally broken aluminium: Has an insulating strip inside the frame that blocks heat flow. A good middle ground.
• uPVC: Excellent insulation, low maintenance and widely used in double glazing.
• Timber: Naturally insulating and attractive, but needs regular painting or oiling.

How to compare windows properly

Two numbers tell you most of what you need to know. Look for them on quotes or through the Window Energy Rating Scheme (WERS):

• U-value: How easily heat passes through the whole window. Lower is better. A single glazed aluminium window can be around 6.9, while a double glazed timber or uPVC window can be around 3.0 or lower.
• SHGC (solar heat gain coefficient): How much of the sun's heat gets through, from 0 to 1. A lower number keeps more heat out, which suits hot, sunny windows. A higher number lets in more free winter sun, which suits north-facing windows in cooler areas.

Ask your supplier for WERS-rated windows so you're comparing like with like, rather than relying on marketing claims.

Is double glazing worth it?

It's a long-term investment rather than a quick win, so the honest answer is: it depends on your home and climate.

Double glazing is usually worth it if:

• You live somewhere with cold winters, such as Melbourne, Canberra, Hobart or alpine areas
• You're renovating or replacing old, leaky windows anyway
• You have large windows or glass sliding doors
• Road, rail or aircraft noise bothers you
• Condensation and mould are a regular problem

It may be lower priority if:

• You live in a mild climate with comfortable winters
• Your ceiling isn't insulated yet. Our ceiling insulation guide explains why that's often a cheaper, bigger win to tackle first
• Your budget is tight, in which case secondary glazing, heavy curtains or draught sealing can get you part of the way for much less

Cheaper ways to improve your windows today

If double glazing isn't in the budget right now, these can still help a lot:

1. Thick, close-fitting curtains with a pelmet. A pelmet stops warm air sneaking over the top of the curtain.
2. Honeycomb (cellular) blinds. Their air pockets add a surprising amount of insulation.
3. Draught sealing. Weather strips around window sashes are cheap and easy to fit.
4. External shading. Awnings, eaves or outdoor blinds stop summer sun before it hits the glass.
5. Window film. Low-E or tinted films can reduce heat gain and loss on existing glass.

Frequently asked questions

How much does double glazing cost per window in Australia?

Retrofitting double glazing into an existing frame often costs around $400 to $1,200 per window, while a brand new double glazed window installed can range from about $600 to more than $2,000 depending on size and frame.

Does double glazing really make a difference?

Yes. Windows can account for up to 40% of heat loss in winter, and double glazing can roughly halve the heat lost through the glass. Most people notice warmer rooms, less condensation and less outside noise.

Can I double glaze my existing windows?

Often, yes. If your frames are in good condition and deep enough, a glazier can retrofit double glazed units. Secondary glazing is another option that works with almost any existing window.

How long does double glazing last?

Good quality double glazed units commonly last 20 years or more. If you see fogging or moisture between the panes, the seal has failed and the unit may need replacing.

The bottom line

Double glazed windows make a home warmer, quieter and more comfortable, and they cut the heat that slips out through one of the weakest parts of the house. They're not the cheapest upgrade, so they make the most sense in colder climates, during renovations or where noise is a problem.

If you're on a tighter budget, start with ceiling insulation, draught sealing and good curtains, then plan for double glazing room by room. Get a few quotes, ask for WERS ratings and compare frame types before you commit.

Prices and performance figures are general estimates as of October 2026 and will vary with your home, location and product. Always get quotes from qualified glaziers and window suppliers. See our disclaimer for more.