Embodied Carbon in Buildings: What Australian Builders Actually Need to Measure

Three materials — concrete, steel, and aluminium — account for more than 70% of a typical building's embodied carbon footprint, according to the Green Building Council of Australia. That carbon is baked in before anyone turns on a light switch, before a tenant signs a lease, before the building even has an occupancy certificate. And here's the part that catches people off guard: as Australia's electricity grid decarbonises, the proportion of a new building's lifetime emissions that comes from its materials is climbing from roughly 16% today toward 85% by 2050.

That inversion is why embodied carbon in buildings and construction in Australia has gone from a niche concern for sustainability consultants to something that project directors and quantity surveyors need to understand. The GBCA already requires a minimum 10% embodied carbon reduction for any Green Star-rated building. The NCC 2025 introduces voluntary embodied carbon reporting for commercial buildings. And Infrastructure Australia's 2024 projections put upfront embodied carbon from our buildings and infrastructure pipeline at about 10% of national emissions — roughly 37 to 64 million tonnes of CO2-e per year.

That's not a rounding error. That's the equivalent of running Australia's entire domestic aviation sector several times over. And most of it is being measured poorly or not at all.

The Grid Is Getting Cleaner. Your Concrete Isn't.

For decades, operational energy — the electricity and gas consumed during a building's 50-to-60-year life — dominated the emissions conversation. Fair enough. A commercial office in Victoria running on the state grid at 0.78 kg CO2-e/kWh racks up serious Scope 2 numbers over time. The logical response was energy efficiency: better insulation, LED lighting, efficient HVAC, solar PV on the roof.

But the grid is decarbonising faster than most people expected. South Australia's grid factor has dropped to 0.22 kg CO2-e/kWh. Tasmania sits at 0.20. Even Victoria and Queensland are trending down year on year. The NCC 2025 updates push operational energy performance harder still, tightening requirements for building envelope, HVAC efficiency, and on-site renewables. We covered the state-by-state NGA emission factors — and why they matter for Scope 2 calculations — in an earlier post.

So operational carbon is shrinking. But the carbon in your materials hasn't changed. A tonne of Portland cement still emits roughly 600-900 kg of CO2 during production, depending on the kiln type and fuel mix. Structural steel still sits around 2.2 kg CO2-e per kilogram. Aluminium — used in window frames, curtain walls, cladding — is around 20 kg CO2-e per kilogram, making it one of the most carbon-intense building materials by weight.

The GBCA has modelled this crossover. For a new all-electric home, upfront embodied emissions are already more than seven times the operational emissions over a 60-year life. The average detached house locks in about 185 tonnes of CO2-e just from its materials and construction. If it's solar-powered, the operational emissions over 60 years approach zero. So the embodied carbon isn't just relatively more important — it's almost the entire emissions story.

For Australian builders and developers facing ASRS climate disclosures and Scope 3 reporting obligations, this means the conversation about building emissions is fundamentally shifting. You can't efficiency-your-way out of emissions that are already locked into the structure before the scaffolding comes down.

What Exactly Counts as Embodied Carbon

Embodied carbon includes all the greenhouse gas emissions associated with a building's materials and construction processes — everything except the energy consumed during the building's operational life (that's Scope 2 and operational Scope 1).

The international standard EN 15978 breaks a building's life cycle into stages, and this is where the measurement gets specific.

Product stage (A1-A3): Raw material extraction, transport to factory, and manufacturing. This is where the bulk of embodied carbon sits. When someone says "the embodied carbon of concrete is 0.2 kg CO2-e per kilogram," they're usually talking about A1-A3 — cradle to gate. It covers the limestone quarrying, the cement kiln, the grinding and mixing, and the transport between those steps.

Construction stage (A4-A5): Transport of materials to site, plus the construction process itself — cranage, formwork, welding. These stages add maybe 5-15% on top of the product stage for most buildings, but they vary a lot depending on site logistics.

Use stage (B1-B5): Maintenance, repair, replacement, and refurbishment over the building's life. Replace a curtain wall at year 25? That replacement's embodied carbon gets counted here. This is often excluded from early-stage assessments because it requires assumptions about building lifespan and maintenance schedules that are hard to pin down.

End-of-life (C1-C4): Demolition, transport, waste processing, disposal. And then there's Module D — the potential benefit from reusing or recycling materials beyond the building's system boundary.

Most Green Star and NCC assessments focus on A1-A3 (product stage) as the minimum. That's pragmatic. It captures the biggest chunk of embodied carbon using data that's actually available — mainly from Environmental Product Declarations. But it misses the full picture, and we're honest about that. A1-A3 is necessary but not sufficient.

EPDs: The Data Source You'll Need to Learn to Read

An Environmental Product Declaration is a standardised, third-party-verified document that reports the environmental impact of a specific product across its life cycle. Think of it as a nutrition label for building materials — except instead of calories and sodium, you get global warming potential (GWP), ozone depletion, acidification, and a dozen other impact categories.

EPDs in Australia follow ISO 14025 and EN 15804, and they're registered through EPD Australasia (the regional programme operator for the International EPD System). They're also recognised for Green Star credits and ISC infrastructure ratings.

Here's how to actually read one — because we've watched people stare at these documents for twenty minutes and still not find the number they need.

Find the GWP-total line in the results table. That's your embodied carbon number. It'll be expressed in kg CO2-e per declared unit (which might be per tonne, per cubic metre, or per square metre depending on the product). Make sure you know which life cycle stages are included — most product EPDs cover A1-A3, but some include A4, C, and D.

Check the declared unit. An EPD for ready-mix concrete might declare results per cubic metre. An EPD for structural steel might use per tonne. An EPD for insulation might use per square metre at a specified thickness. If you're comparing products, the declared units need to match — or you need to convert.

Look at the validity date. EPDs are typically valid for five years. An expired EPD is better than no data, but a current one is what Green Star assessors want to see.

Watch for product-specific vs industry-average EPDs. A product-specific EPD tells you the actual carbon intensity of that manufacturer's product from that factory. An industry-average EPD gives you a generic number for the product category. Product-specific EPDs are more useful for project-level calculations because they reward manufacturers who've actually invested in decarbonisation — and they give you more defensible data for your Scope 3 reporting.

The reality is that EPD availability in Australia is still patchy. Major concrete suppliers like Boral, Holcim, and Hanson publish EPDs for their main product lines. The big structural steel producers (BlueScope, InfraBuild) have them. But once you get into specialty products — specific insulation brands, certain cladding systems, imported glass — you'll hit gaps. When there's no EPD, you fall back to generic data from databases like AusLCI or the GBCA's upfront carbon benchmarks. That generic data is less accurate but it's better than pretending the emissions don't exist.

We built Carbonly's LCA module specifically to handle this mix of data quality. You can import product-specific EPDs directly, pull from our materials library where we've pre-loaded common Australian construction products with their declared GWP values, or use industry-average factors as a fallback — with the data source tracked so your auditor can see exactly where each number came from.

What the Regulators and Rating Bodies Are Doing

The regulatory picture for embodied carbon in Australia is moving — but it's not moving as fast as some people think. And that gap between expectation and reality is where builders get tripped up.

NCC 2025 (published February 2026, states can adopt from May 2026) introduces a voluntary pathway for commercial buildings to calculate and report embodied carbon. The keyword is voluntary. There's no mandatory limit, no pass-fail threshold. The Australian Building Codes Board has published guidance on the calculation methodology, and the recommended approach follows the NABERS framework. The expectation — stated by the GBCA and others — is that mandatory embodied carbon standards are being considered for the NCC 2028 update. So you've got roughly two years to learn the methodology before it might become compulsory.

Green Star Buildings v1.1 (registration required from 1 May 2026) requires all rated buildings to address upfront carbon. Since 2020, the minimum has been a 10% reduction in embodied carbon against a reference building. For higher ratings, that jumps to 20%. The GBCA's stated trajectory is a 40% reduction target by 2030. Green Star Homes v1.1, also due in 2026, will extend upfront carbon requirements to residential — either per square metre or within a total carbon budget.

Infrastructure Sustainability Council (ISC) ratings for infrastructure projects already weight life cycle assessment and embodied carbon heavily. Their certified projects have collectively avoided over 1.35 million tonnes of lifecycle materials emissions since 2018. If you're working on public infrastructure — roads, rail, water, energy — the ISC rating is increasingly a tender requirement, and embodied carbon measurement is a big part of earning credits.

ASRS (AASB S2) doesn't explicitly mention embodied carbon by name, but it requires disclosure of Scope 3 emissions where material. For a construction company or developer, purchased goods and services (Scope 3 Category 1) and capital goods (Category 2) are where embodied carbon of materials sits. If you're an ASRS Group 2 reporter (mandatory from July 2026), you can't credibly claim your Scope 3 is immaterial when your business literally pours thousands of tonnes of concrete every year. We covered the full construction carbon accounting picture — including diesel Scope 1 and site power Scope 2 — in a companion post.

How to Actually Measure Embodied Carbon for a Commercial Building

This is where it gets practical. Say you're the sustainability lead on a 15-storey commercial office tower in Brisbane. Gross floor area around 25,000 square metres. Here's roughly what's involved.

Step 1: Get the bill of quantities. You need a reasonably detailed material schedule — tonnes of concrete by grade, tonnes of structural steel, square metres of facade glass, tonnes of reinforcing bar, cubic metres of timber, kilograms of aluminium framing, and so on. The QS usually has this, at least in preliminary form, by the end of schematic design. The earlier you do this assessment, the more influence you have over material choices — but the less accurate your quantities are. That tension never fully resolves.

Step 2: Match materials to emission factors. For each material line item, you need a GWP factor in kg CO2-e per unit. The hierarchy goes: product-specific EPD first, then industry-average EPD, then generic database factor. For a typical Australian commercial building, you might get product-specific EPDs for concrete and steel (because the major suppliers publish them) but fall back to generic factors for some fit-out items.

Here's what the numbers look like for common structural materials, using typical Australian factors:

Material	Typical GWP (kg CO2-e/kg)	Notes
Concrete (standard 40 MPa)	~0.15-0.20	Varies significantly with cement content and supplementary cementite materials
Structural steel (fabricated sections)	~2.0-2.5	BlueScope and InfraBuild publish product-specific EPDs
Reinforcing bar (rebar)	~1.2-1.8	Often from electric arc furnace with high recycled content
Aluminium (extruded)	~15-20	Depends heavily on smelting electricity source
Flat glass	~1.2-1.4	Float glass; rises with coatings and lamination
Engineered timber (CLT/glulam)	~0.3-0.5	Can be negative if biogenic carbon is counted

Step 3: Multiply and sum. Tonnes of material multiplied by kg CO2-e per kg gives you kg CO2-e per material. Sum across all materials for your A1-A3 total. For a 25,000 m2 commercial office, a reasonable ballpark is 400-500 kg CO2-e per square metre of gross floor area — so 10,000 to 12,500 tonnes of CO2-e locked into the structure and facade before anyone plugs in a laptop. That's a big number. For context, it's roughly equivalent to the annual operational emissions of 5,000-6,000 average Australian homes.

Step 4: Model substitutions. This is where it gets interesting. What happens if you swap the aluminium curtain wall for a timber-aluminium hybrid? What if you specify 30% supplementary cementitious materials in the concrete to reduce the Portland cement content? What if you use recycled-content steel instead of virgin? Each substitution changes the total, and the differences can be material — pun intended. The 25 King Street project in Brisbane achieved nearly 40% upfront emissions savings through material substitutions, primarily by using engineered timber where conventional designs would use concrete and steel. Quay Quarter Tower in Sydney saved over 12,000 tonnes of CO2 by retaining 65% of the original 1976 structure.

We built the scenario builder in Carbonly's carbon planning module for exactly this kind of modelling. You load your bill of quantities, assign emission factors from EPDs or our materials library, and then test material swaps to see the impact on total embodied carbon — without rebuilding a spreadsheet from scratch every time someone asks "what if we used CLT for the upper floors?"

Where This Still Gets Messy

We'd be lying if we said embodied carbon measurement was a solved problem. It isn't. A few honest admissions.

Data gaps are real. For structural materials — concrete, steel, timber — EPD coverage in Australia is decent and improving. For everything else, it ranges from patchy to nonexistent. Try finding a verified EPD for the specific brand of acoustic ceiling tile specified on your project. Or the exact waterproofing membrane. Or the imported stone cladding from a quarry in Turkey. You'll end up using generic factors for maybe 30-40% of your material palette, and those generic factors carry uncertainty ranges that nobody likes to talk about.

System boundaries create apples-to-oranges problems. One EPD covers A1-A3. Another covers A1-A5 plus C and D. If you're comparing two concrete products and one includes transport to site (A4) and the other doesn't, you're not comparing like with like. The EN 15804+A2 amendment tries to standardise this, but uptake among Australian EPD publishers is still inconsistent.

Biogenic carbon accounting for timber is genuinely confusing. Does the carbon stored in a CLT floor panel count as negative emissions? It depends on the methodology. EN 15804 says report it separately. Some LCA tools net it off. The GBCA's upfront carbon calculator has its own approach. If someone tells you "this timber building is carbon negative," ask them to show you exactly how they've treated biogenic carbon in the A1-A3 and C3-C4 modules. The answer matters.

And Scope 3 boundary-setting for builders is awkward. If you're a main contractor, the embodied carbon of concrete and steel you procure is your Scope 3 Category 1. But if you're a developer, it might sit in Category 2 (capital goods). If you're a subcontractor, it could be entirely outside your reporting boundary. Who "owns" the embodied carbon depends on the GHG Protocol scope definitions and your organisational boundary. Different companies on the same project end up counting (or not counting) the same materials. That's not wrong — it's just how the framework works — but it creates confusion when a client asks for the building's total carbon footprint and gets three different answers from three different parties.

The Commercial Reality

None of this stays academic for long. The GBCA estimates that without intervention, new housing construction alone will lock in 426 million tonnes of CO2-e over the next 25 years — nearly 11% of Australia's remaining carbon budget to 2050. KPMG's analysis suggests embodied carbon from construction is projected to grow 65% by 2050 if current practices continue.

But the flip side is real too. Low-cost material substitutions — higher recycled content, supplementary cementitious materials, design optimisation — can achieve 24-46% reductions in embodied carbon without radical changes to building design. That's not hypothetical. That's demonstrated on real projects, using materials that are commercially available in Australia today.

The builders and developers who start measuring now — even imperfectly, even with data gaps — will have two years of baseline data by the time the NCC 2028 potentially makes embodied carbon mandatory. They'll know which suppliers can provide EPDs and which can't. They'll have tested material substitutions on actual projects and know which ones the engineering team will accept. And they won't be scrambling to build a measurement system from scratch when the requirement drops.

If you're running construction projects and already tracking diesel and electricity for NGER or ASRS, embodied carbon is the logical next layer. Start with the structural materials — concrete and steel — because that's where the tonnage lives and the EPD data is most available. Get your QS to include GWP alongside cost and weight in the bill of quantities. And build the data collection habit now, because it's not getting simpler from here.

Related Reading:

If you're measuring embodied carbon across construction projects and want a system that handles EPDs, material libraries, and scenario modelling in one place — talk to the Carbonly team. We built the LCA module for exactly this problem.