Low-carbon aluminium lowers the carbon spent making a façade. What you do with the envelope decides the rest. A practical guide for the teams that design, specify and deliver it.
Meeting the ventilation challenges of modern apartment buildings
Every material you specify carries a set of numbers. Thermal performance, acoustic rating, water resistance, structural capacity: the metrics that tell you whether a product does its job. There’s a newer one now appearing on data sheets, turning up in tender requirements, and heading for the rating tools you already use: the material’s carbon figure. It’s recent enough that it hasn’t yet had the same scrutiny as the numbers beside it, which is exactly why it is worth a proper look.
Because that figure is set to carry real weight in specification, it’s worth understanding properly rather than taking at face value. What follows is a practical read on what it means on a project, rather than the version that tends to appear in marketing.
There’s also a second half to it that most of the conversation skips. The carbon a façade costs to make is only the first cut. The carbon it costs to run, meaning how hard the building has to work to stay comfortable across its life, is the second, and the envelope you specify governs both. Get the material right and you’ve cut carbon once. Get the performance right and you’ve cut it twice. This article works through both.
Why the aluminium figure is the one to watch
Aluminium is a superb building material: light, strong, durable and endlessly recyclable. It is also, in its conventional form, energy-intensive to produce, and that energy shows up as a carbon figure noticeably higher per kilogram than concrete or steel.
That matters for specification because the figure isn’t fixed. The same alloy, delivering the same structural and thermal performance, can carry very different carbon numbers depending on how it was made. Two products that look identical on every performance metric can therefore sit worlds apart on the carbon line, and increasingly, that line is the one a rating tool or a tender is asking about.
So this isn’t really a values question. It’s a specification question. When the number turns up in the brief, the useful thing is knowing how to read it rather than taking the data sheet’s word for it.
The ground is already shifting
This is worth paying attention to even if you are sceptical of the whole sustainable-materials conversation, because the rules are changing regardless of what anyone believes about them.
Since July 2024, the Australian Government’s Environmentally Sustainable Procurement Policy has required suppliers on construction procurement over $7.5 million to measure and report the embodied carbon of what they deliver. That is a live reporting obligation on a large slice of public work, not an aspiration. Alongside it, NABERS, the rating system many projects already use for operational performance, is developing an embodied carbon rating tool, so buildings will be able to measure and compare their upfront carbon much as they already compare energy. Green Star rewards recycled content and lower-carbon materials, and government tenders increasingly weight low-emission materials the same way they weight cost and compliance.
None of that asks you to hold an opinion about anything. It simply means the metric is arriving in the briefs, tenders and rating tools you already work with, and it is quickly becoming one worth being fluent in before it appears in a live submission. The scale is worth appreciating too. According to Infrastructure Australia’s 2024 report on embodied carbon, the built environment is directly responsible for close to a third of Australia’s emissions, and most of a project’s upfront carbon comes from the manufacture of its materials. When a number lands on that scale, it tends not to stay optional for long. Specifying without regard to it is becoming a commercial risk in the same way that missing an acoustic or fire requirement is, and it has little to do with virtue.
So what actually moves the number?
Here is the useful part. Almost all of aluminium’s carbon figure comes from a single place, which means almost all of it can be changed. The number is set at the smelter, during the electrolysis that produces the metal, and that process is so electricity-hungry that the outcome depends overwhelmingly on where the power comes from.
Change the inputs and the figure moves dramatically. Two levers do most of the work.
The first is renewable-powered smelting. When that electrolysis runs on hydropower rather than coal-fired grid power, the figure for primary aluminium falls to around a quarter of the global average. It is the same metal, with the same strength and durability, carrying a fraction of the embodied carbon.
The second is recycled content. Re-melting existing aluminium skips the smelting step almost entirely, so it uses only a fraction of the energy, and high recycled-content products carry some of the lowest figures available. One distinction is worth knowing so you can read a claim properly. Post-consumer scrap, genuinely recovered from end-of-life products, is a more meaningful credential than pre-consumer scrap, which is really just factory offcuts that were never headed for landfill in the first place.
It is also worth noting an industry-level point while it is relevant. Australia currently exports most of its aluminium scrap rather than recycling it here, which is why the highest recycled-content metal is often imported today, a gap that domestic recycling capacity is expected to narrow over time. It is a useful reminder that “lowest carbon” and “shortest supply chain” do not always point to the same product, and both are legitimate things to weigh on a project.
The figures worth carrying into a specification conversation
The following rough hierarchy is useful for sense-checking any claim a supplier puts in front of you:
- ~20 kg CO₂e/kg for conventional primary aluminium, the high end, and the reason the conversation exists
- ~8 kg CO₂e/kg for typical recycled-content billet
- ~4 kg CO₂e/kg for renewable-smelted primary, or premium low-carbon lines
- ~2 kg CO₂e/kg for high recycled-content aluminium at 75 per cent or more post-consumer scrap
These are order-of-magnitude reference points rather than product specs. The real figure for any product should come from its documentation, and a little familiarity with how these numbers are put together goes a long way.
Reading the number properly
“Low-carbon” is not a regulated term, so the figures behind it reward a second look. Less because anyone is being dishonest, and more because a number without context cannot really be compared to anything.
Scope is usually where it matters most. A carbon figure only means something once you know its boundaries: whether it covers the raw billet or the finished, fabricated system, and how much of the supply chain, from mining and refining through smelting and transport, sits inside it. Two figures drawn to different boundaries are not comparable however similar they look, so it is worth confirming what each one actually measures before it goes into a comparison.
Independent verification is the next signal to look for. An EPD, or equivalent third-party data, tells you a figure has been checked against a common standard rather than self-declared. It is worth remembering that product-level EPDs remain uneven across fabricated façade systems, so verification often lives at the material or component level rather than the whole assembly, and knowing which one you are looking at is part of reading the claim.
Then there is material transparency more broadly. Frameworks like Declare, effectively a nutrition label for building products, set out what is actually in a product and whether it avoids hazardous substances, such as a Red List Free designation. For Green Star projects, and for anything pursuing the Living Building Challenge, that disclosure is part of the credit itself rather than a supporting detail.
The second cut: performance
This is the half of the story that the material conversation tends to skip, and it is where the envelope really earns its keep.
The strongest outcome comes from treating both as the same problem. A lower-carbon material is a good start on the first. An envelope that also reduces the building’s reliance on mechanical heating and cooling, through genuine natural ventilation, effective sealing when closed and solid thermal performance, keeps paying back on the second long after handover. Material and performance are not two separate conversations. They are one, and the shape of it is simple: spend less making the envelope, then spend less running it. And the numbers back the effort in both directions: the Clean Energy Finance Corporation reports that sustainability-rated projects can cut embodied carbon by up to a third, and that typical projects can achieve around an 18 per cent reduction in embodied carbon while trimming material costs by roughly three per cent.
There is a timing point worth stating plainly here, because it is the part that sits with the designer rather than the supplier. Infrastructure Australia points to the earliest stages, in the needs and design decisions, as where the greatest opportunity to reduce a building’s carbon lies, with that opportunity shrinking steadily as a project moves toward procurement and construction. By the time carbon appears as a line in a post-tender contract, most of the opportunity to influence it has already passed. The leverage, in other words, is not really at the loading dock. It is on the drawing board, and the specifier who considers the envelope’s whole-life carbon early holds a lever that the rest of the chain has already lost.
That is the whole idea behind cutting carbon twice. Lower the carbon spent making the envelope, then lower the carbon spent running it, and make both calls early, at the point where they can still be made. It is not really a sustainability pitch. It is simply a better building.
What it looks like when it's done properly
The theory becomes a good deal more convincing when you can stand in front of a finished building. At Ngā Mokopuna, formerly the Living Pā, Victoria University of Wellington’s flagship facility designed by Tennent Brown Architects, the project pursued Living Building Challenge 4.0 certification, one of the most demanding sustainability standards in the world. The operable louvre systems were manufactured using Hydro CIRCAL 75R, a low-carbon aluminium made from a minimum of 75% post-consumer recycled content, with a certified maximum footprint of around 1.9 kg CO₂e per kilogram — roughly eight times lower than the global primary-aluminium average. Every component was Red List Free.
That single project holds the whole argument. It pairs a named product with a verified recycled-content figure and independent transparency compliance, which is the opposite of a vague claim. It also shows the two levers working together, because the same louvres that deliver the low embodied figure are what let the building breathe naturally and lean on passive design instead of mechanical cooling. Low carbon to make, low energy to run, all in one specification decision.
You can read the full story of the project here.
Safetyline Jalousie manufactures performance louvre window systems in Australia using EPD-backed low-carbon aluminium, with systems that are Red List Free on the Declare database. We build for both halves of the equation: responsible materials, and the natural-ventilation performance that lowers a building’s energy demand across its whole life.
If you would like to go deeper on façade performance and material selection, you are welcome to explore our Sustainability page, or to book a CPD session on sustainability and breathable buildings for your studio.
