Double glazing is one of the first upgrades people consider when a house is too cold in winter, too hot in summer or too noisy. It is also one of the easier ones to overspend on. In Adelaide, the honest answer to “is it worth it?” is: often yes, but not everywhere, and not on pane count alone.
This guide explains what double glazing does in Adelaide’s climate, where it tends to deliver the most, where the return is weaker, and what to ask for when you are specifying windows.
The short answer
Double glazing usually makes the most sense when you are building, renovating or replacing windows anyway, in rooms you heat and cool regularly, and where you also want less noise or condensation. It makes less sense as a standalone retrofit on small, shaded windows in rarely used rooms. In every case the whole window matters: glass, frame, orientation and installation.
What double glazing actually is
A double glazed window uses an insulated glass unit (IGU): two panes of glass separated by a sealed gap, usually filled with air or a gas such as argon. The gap slows the transfer of heat compared with a single pane. Low-E (low-emissivity) coatings can be added to reduce radiant heat flow further.
Two measurements tell you how a window performs:
- U-value (Uw for the whole window): how easily heat passes through. Lower is better in almost every climate.
- Solar Heat Gain Coefficient (SHGC): how much of the sun’s heat passes through. Whether a lower or higher figure is better depends on climate and orientation.
These figures are normally published for the whole window, glass and frame together, through the Window Energy Rating Scheme (WERS) or equivalent testing and simulation. A glass-only figure is not a window rating.
Why Adelaide is not Melbourne (or Perth)
Adelaide falls in National Construction Code climate zone 5. Manufacturer 7-star guides, citing the ABCB map, place coastal South Australia including Adelaide in this zone. It is a mixed, warm temperate climate where homes need both winter heating and summer cooling.
That changes the specification. For zones 4 and 5, window makers recommend a low U-value and a low SHGC so the window both holds winter warmth in and keeps summer sun out. Advice written for colder, heating-dominated places, where capturing free winter sun is the priority, does not carry over neatly.
In practical terms, the double glazing question in Adelaide is rarely just “double or single?”. It is also “which glass coating, for which orientation, in which frame?”
How much difference can it make?
The Your Home guide reports that up to 40% of a home’s heating energy can be lost, and up to 87% of its heat gained, through windows. Renew adds that in cold and mixed climates a double glazed window can cut window heat loss by 60% or more compared with single glazing.
To make that concrete, the table below uses one manufacturer’s published WERS-rated awning window figures as an illustration. They are not Alum Windows figures, and results vary by product, frame and glass.
| Glazing option (example awning window) | Uw | SHGC |
| Clear single glazing | 6.4 | 0.63 |
| Low-E single glazing | 4.9 | 0.41 |
| Clear double glazing (IGU) | 4.1 | 0.57 |
| Low-E double glazing (IGU) | 3.3 | 0.45 |
Two things stand out. Moving from single to double glazing lowers the U-value substantially. And a coating can matter as much as the second pane: low-E single glazing in this example has a lower SHGC than clear double glazing. For an Adelaide west-facing window that bakes in summer, that is a real consideration.
Where double glazing tends to pay off
New builds and major renovations. Window upgrades cost far less when you are already building or replacing frames. Energy ratings for new homes also set glazing targets through NatHERS, and your assessor will specify the U-value and SHGC needed. Double glazing is one way to meet them, but the requirement is a whole-house result, not a rule that every window must be double glazed. Confirm current requirements with your assessor or certifier.
Living areas and bedrooms you heat and cool daily. The more hours a room is conditioned, the more a better window earns back.
Large windows and glazed doors. Big areas of glass are where the biggest heat flows happen.
Hot east and west exposures. Here the glass coating (low SHGC) often matters as much as the extra pane, and double glazing gives room for a high-performance coating on the right surface.
Noisy locations. Homes near arterial roads, tram lines or the airport flight path can benefit from the extra glass mass and air gap, especially when laminated or acoustic glass is used. Noise reduction depends on the glass build-up rather than the number of panes, so ask for an acoustic rating rather than assuming.
Condensation problems. Double glazing keeps the inner pane warmer, which RACV notes reduces condensation and the mould that can follow. Ventilation still matters.
Replacing old, leaky aluminium windows. Old, uninsulated frames lose heat quickly and often leak air. Replacing them can improve comfort for reasons beyond the glass.
Where it may not pay off
Small, shaded or rarely used windows. A laundry or storeroom window that is seldom conditioned will rarely recover a higher cost through energy savings.
Retrofit onto frames that cannot support it. Double glazing is heavier and thicker. If your existing frames cannot take it, you are replacing the window, which changes the economics.
When the cheaper fixes are still undone. Draught sealing, ceiling insulation, external shading and curtains with pelmets can deliver more per dollar. A window upgrade will not fix a leaky, uninsulated roof space.
Short time horizons. If you plan to sell soon, a well-specified upgrade may help comfort and appeal, but payback should not be assumed.
Triple glazing. RACV notes triple glazing is widely used in Northern Europe but double glazing is the typical choice in Australia. It adds cost and weight, and Adelaide’s mixed climate makes a high-performance double glazed unit in a good frame a more common target.
Honest caution on payback. Published payback claims vary widely, and most online cost calculators are not built for Adelaide. One independent cost guide estimates retrofitting double glazing at roughly $550 to $1,500 per window in Adelaide. Treat figures like this as a broad indication only and rely on written quotes for your own project.
The frame matters as much as the glass
Aluminium is strong, slim and durable, but it conducts heat well. In a standard aluminium frame, heat can bypass the insulating glass by travelling through the frame itself. A thermal break is a low-conductivity barrier, often polyamide, built into the frame to interrupt that path. Alspec, one of Australia’s major aluminium extruders, describes its thermally broken systems as accommodating double glazed units and publishes whole-window Uw values as low as 1.7 for some configurations.
The lesson is not that every double glazed aluminium window needs a thermal break. It is that a high-performance glass unit in a conductive frame will not perform like its glass figure suggests. Ask for the whole-window rating, not just the glass.
A simple way to decide
Work through these questions window by window.
- Is this window being replaced or built new anyway? If yes, double glazing is usually easier to justify.
- How often is the room heated or cooled? Daily use strengthens the case.
- Which way does it face? West and east need SHGC attention. North may allow some winter sun capture; discuss with your designer or energy assessor.
- Is noise an issue? If so, ask for an acoustic specification, not just “double glazing”.
- Is condensation or mould a problem? Consider frame, glass and ventilation together.
- What do your plans or energy assessment require? Use the specified U-value and SHGC as a brief.
- Have the cheaper fixes been done? Seal, insulate and shade first if not.
What to ask a window supplier
- What is the whole-window Uw and SHGC for this exact configuration, and is it WERS-rated or otherwise tested?
- Is the frame thermally broken? If not, how does that affect the whole-window figure?
- What glass is proposed (low-E, laminated, acoustic), and why for each orientation?
- What gas fill and spacer are used, and what is covered by the warranty?
- Does the design comply with the relevant Australian Standards for this application?
Common mistakes
- Choosing on “double glazed” alone, without checking the whole-window rating.
- Using the same glass on every elevation.
- Specifying a high-performance IGU in a standard conductive frame and expecting the glass figure.
- Ignoring ventilation and then blaming the windows for condensation.
- Assuming an upgrade also solves noise, without an acoustic specification.
Where Alum Windows fits
Alum Windows is an Adelaide manufacturer of custom aluminium windows and doors, fabricated at its Edinburgh, South Australia facility using Alspec extrusions and backed by a 7-year manufacturer’s warranty. The business says its windows are designed to take a range of glass types, and that its designers can help you work toward a specified U-rating using single or double glazing, low-E, laminated or thickened glass. Frame and glass options vary by project, so confirm what is available for your windows and doors, including whether a thermally broken configuration suits your project, when you request a quote.
If you are comparing options, start with the aluminium windows range, such as awning windows and sliding windows, and the aluminium doors range for glazed openings.
Frequently asked questions
Is triple glazing worth it in Adelaide?
For most Adelaide homes, a well-specified double glazed unit in a good frame is the more common choice. Triple glazing adds cost and weight and is usually considered only for demanding performance targets.
Does double glazing reduce noise?
Yes, it can, but the amount depends on glass thickness, laminated or acoustic layers and the air gap rather than the pane count alone. If noise is your main concern, ask for an acoustic rating.
Will double glazing stop condensation?
It reduces condensation on the inside of the glass because the inner pane stays warmer, but it will not remove it entirely. Frame performance, indoor humidity and ventilation also matter.
Can I add double glazing to existing windows?
Sometimes. Options reported in New Zealand guidance include replacing the window, fitting double glazed inserts into sound existing frames, or adding secondary glazing; suitability depends on the frame and should be assessed by a supplier. Check what applies to your window type and local requirements.
Do I need double glazing to meet energy requirements for a new home?
Not as a blanket rule. Energy compliance is assessed for the whole house against the climate zone, and your energy assessor will set window U-value and SHGC targets. Double glazing may be one way to meet them.
Next step
Before you request quotes, note which rooms you use most, which direction each window faces and whether noise or condensation is an issue. Then ask suppliers for whole-window Uw and SHGC figures for each option. To discuss windows or doors for your project, contact the Alum Windows team for a free quote.
General information only. It is not engineering, energy-assessment or compliance advice; confirm requirements for your project with your designer, energy assessor and certifier.