uPVC frames insulate better than standard aluminium, while aluminium frames can be slimmer and suit large sliding doors. In the NSW BASIX default window data, a double glazed aluminium window has a U-value of 4.8, thermally broken aluminium 3.6 and uPVC 3.0, where lower is better. As of October 2026 we found no independent Sydney price guide showing either material is reliably cheaper once installed.
- NSW BASIX default data for double glazed, clear glass windows: aluminium U-value 4.8, thermally broken aluminium 3.6, timber or uPVC 3.0.
- YourHome says uPVC frames often insulate better than timber or thermally broken aluminium.
- Near the sea, aluminium relies on its coating: Dulux says its Duralloy powder coat suits sites more than 100 m from the high tide line.
- Both materials are sold in bushfire-rated systems: Bradnam’s aluminium and aluplast uPVC both claim ranges tested to BAL-40.
- The NSW Government puts new double glazed windows at $600 to $2,000 or more per window installed, depending on size and frame material.
What is the difference between uPVC and aluminium windows?
uPVC windows have frames made from rigid, unplasticised PVC, a type of plastic. Aluminium windows have metal frames, usually powder coated or anodised. Both can hold single, double or triple glazing.
The big difference is heat. Aluminium is a very good conductor, so YourHome warns it lowers the insulating value of the glass unless the frame is built to reduce this. A thermally broken aluminium frame has an insulating strip inside it to slow heat flow. uPVC is a poor conductor, which is why it is often used for double glazing.
uPVC vs aluminium at a glance
This table compares the two materials, with thermally broken aluminium as the middle option.
| Factor | uPVC | Standard aluminium | Thermally broken aluminium |
|---|---|---|---|
| Insulation, double glazed clear (U-value, lower is better) | 3.0 | 4.8 | 3.6 |
| Cost | Overlaps with aluminium; one uPVC maker calls them comparable | Airtasker puts aluminium window supply at about $40 to $300 per m² | YourHome says it can be expensive, but prices are falling |
| Coastal salt | Does not rust or corrode; check hardware and reinforcing are also rated for the coast | Depends on the coating; check the warranty distance from the sea | Same as standard aluminium |
| Bushfire (BAL) | Some systems tested to BAL-40 (aluplast); check the exact product | Many systems sold to BAL-40 (for example Bradnam’s); check the exact product | Check the exact product |
| Maintenance | Wipe down; check seals and hardware | Wash coastal frames regularly; clean tracks | Wash coastal frames regularly; clean tracks |
| Look | Frames are usually wider than aluminium; ask about colours and styles | Slim frames; suits large sliders | Similar look to standard aluminium |
U-values: NSW Planning Portal BASIX default window data (awning and casement windows). Rated products can perform better than these defaults. Other sources as listed under each section. Check figures for the exact product you are quoted.
Which is cheaper, uPVC or aluminium windows?
Neither is clearly cheaper once installed, based on the sources we could find in October 2026. Prices depend more on size, glass and installation than on frame material.
- The NSW Government says new double glazed windows cost $600 to $2,000 or more per window installed, depending on size, frame material and other features.
- Airtasker’s aluminium windows guide (July 2026) puts aluminium windows at about $40 to $300 per m², with a Sydney average of $150 per m². These look like supply prices, so installation is extra.
- An older Airtasker guide (July 2024) puts aluminium-framed double glazed windows at about $150 to $1,250 per m².
- Windows Republic, a Melbourne uPVC window maker, puts its uPVC windows at about $1,800 to $3,500 or more per window installed, and says aluminium is in a similar range depending on the specification.
We found no independent Sydney guide that splits installed prices by frame type. The fairest test is to ask each installer to quote the same windows in uPVC, standard aluminium and thermally broken aluminium, with the whole-window U-value and SHGC for each.
If you only want to change the glass, retrofit double glazing into existing frames may be cheaper. Our guide Retrofit Double Glazing Sydney: Cost, Noise, Worth It? explains when that works.
Do uPVC windows insulate better than aluminium?
Yes, in most cases. YourHome says uPVC frames provide excellent thermal performance, often better than timber or thermally broken aluminium.
The NSW BASIX default window data, used in BASIX assessments, shows the gap clearly. With double glazed clear glass, aluminium is rated at a U-value of 4.8. Thermally broken aluminium is 3.6. Timber or uPVC is 3.0. With low-e glass and argon, timber or uPVC drops to 2.0, while thermally broken aluminium with high solar gain low-e glass and argon is 2.9.
For Sydney, also look at the solar heat gain coefficient (SHGC). It shows how much of the sun’s heat comes through the window. West-facing rooms often benefit from a lower SHGC, whatever the frame.
YourHome’s worked example shows why this matters: halving the U-value of a home’s glazing halves the heat flowing through it, from about 6.5 kW to about 3.3 kW in its example. That is the output of a large room heater or air conditioner.
Which is better near the beach?
Both can work near the coast if you choose the right product and finish. Salt air is hard on metal windows in beachside suburbs such as Manly, Cronulla and Bondi.
For aluminium, the coating matters. Dulux Powders says its Duralloy and Precious powder coats suit sites more than 100 m from the high tide line. Its Electro, Duratec and some other ranges suit sites more than 10 m away, and Fluoroset may suit sites closer than 10 m, such as harbours. These warranties only apply when an accredited coater applies the finish.
uPVC does not rust or corrode. Windows Republic, a uPVC window maker, says it will not degrade from salt air, UV or moisture. That is a manufacturer claim, so ask about the steel reinforcing, hinges, locks and screws, which can still corrode, and what the warranty says about coastal sites.
Are uPVC or aluminium windows better for bushfire areas?
Either can be used on bushfire-prone land if the exact window system is rated for your site’s bushfire attack level (BAL). Many Sydney suburbs on the edge of bushland are mapped as bushfire prone, so check your council’s bushfire prone land map first.
- Aluminium: Bradnam’s says its FlameShield aluminium range meets BAL-12.5, BAL-19, BAL-29 and BAL-40, with most products meeting BAL-40.
- uPVC: aluplast says all its uPVC systems can be built for bushfire zones up to BAL-29, and that some of its ranges are tested to BAL-40 under AS 3959-2018.
Neither of those manufacturers claims BAL-FZ (flame zone) for these ranges. Your BAL is set by a bushfire assessment for new work. Ask the supplier for the test report for the exact frame, glass and opening type, and check it refers to the current version of AS 3959.
How much maintenance do they need?
Both need far less upkeep than painted timber. uPVC needs a wipe down and a check of seals and hardware. YourHome describes it as long lasting and needing very little maintenance.
Aluminium windows need their frames washed now and then, more often near the sea, and their sliding tracks kept clean so the rollers run freely. Follow the coating maker’s washing advice, because some warranties depend on it.
What about timber or composite windows?
Timber is the third main choice, and it insulates about as well as uPVC. In the NSW BASIX default data, double glazed timber and uPVC windows share the same U-value of 3.0 with clear glass. Composite frames, which combine materials such as timber and aluminium, are rated at 3.9 with double glazed clear glass, though high-end composite products can do much better.
Timber suits heritage homes and older Sydney styles such as Federation and Californian bungalows, but painted timber needs regular upkeep to stop rot and sticking. If you like the look of timber but not the maintenance, ask about aluminium-clad timber or timber-look finishes, and compare their whole-window ratings the same way.
Rules to check before you order
Replacing windows like for like is often exempt development in NSW, if it meets the set standards. Changing opening sizes, heritage homes and conservation areas may need approval. In strata buildings, double or triple glazed windows are a minor renovation that needs owners corporation approval.
Glazing work worth more than $5,000 including GST needs a licensed contractor in NSW. New windows should be made to AS 2047 and use glass that meets AS 1288. Ask your installer to confirm both on the quote.
Compare quotes on the same windows. Ask each installer for the frame system name, the whole-window U-value and SHGC, the BAL rating if you are on bushfire-prone land, and the coastal warranty conditions. A cheap quote for a lower-rated window is not a saving.
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Frequently asked questions
What is uPVC double glazing?
It is a double glazed window, two panes of glass sealed around a gap, set in a frame made from unplasticised PVC. The frame material is a poor heat conductor, so the window loses less heat than a standard aluminium one. In NSW BASIX default data, double glazed uPVC with clear glass is rated at a U-value of 3.0, against 4.8 for aluminium.
Is thermally broken aluminium as good as uPVC?
Close, but usually not quite. In NSW BASIX default data, thermally broken aluminium with double glazed clear glass is rated at 3.6, against 3.0 for uPVC or timber. YourHome calls thermally broken aluminium one of the best performing frames available. It suits buyers who want slim aluminium frames with better insulation.
Do uPVC windows suit heritage homes?
Often not on the street front. Heritage homes and conservation areas usually need replacement windows that match the original look, which often means timber. Check with your council before you order. Secondary glazing inside the existing window can be another option, because it improves comfort without changing the outside.
How long do uPVC and aluminium windows last?
Both can last for decades when well made and installed. Windows Republic, a uPVC maker, says quality uPVC systems last 30 years or more, but that is a manufacturer figure. For any brand, compare the written warranties on the frame, the glass seal, the coating and the hardware, and ask what voids them near the coast.
Can I mix uPVC and aluminium windows in one house?
Yes. Some owners use uPVC or thermally broken frames in bedrooms and living rooms, and aluminium for large sliding doors. Mixing can look odd on the same wall, so ask your installer about matching colours and sightlines. Every window on the quote should list its own U-value and SHGC.
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