Embodied Carbon Disclosure for Australian REITs and...

A property CFO asked us last month whether embodied carbon was actually in scope for their first AASB S2 disclosure. The answer was uncomfortable. Yes. And no one in the business had a number for it.

This is the awkward truth across Australian real estate right now. Most REITs and developers fall into ASRS Group 2, which means their first mandatory climate disclosure covers the financial year starting 1 July 2026. The operational carbon side is reasonably well understood. NABERS ratings have been around for two decades. Tenant electricity, base building gas, refrigerants. That work is mature.

Embodied carbon is the part nobody has clean data for. And paragraph 29 of AASB S2 asks for it anyway.

Why embodied carbon turned into a disclosure problem

For a long time, embodied carbon was a "leading sustainability practice" topic. Something Green Star projects measured. Something the Green Building Council of Australia talked about at conferences. It was not something a CFO had to disclose to the market.

That changed when AASB S2 was finalised. Under paragraph 29(a)(i), entities must disclose Scope 1, 2 and 3 emissions, broken down category by category for Scope 3. Capital goods sit at Category 2. The use phase of buildings sold to others sits at Category 11. For a developer or REIT, those two categories often dwarf everything else combined.

We have seen rough estimates from European reporters where Category 2 alone runs four to six times larger than the entire operational footprint of a property portfolio in any given year. That is not a rounding error you can footnote away.

What AASB S2 paragraph 29 actually requires

The standard does not say "do embodied carbon." It says disclose Scope 3 by the 15 categories defined in the GHG Protocol. For property companies, the two that matter most are:

Category 2 (capital goods). Emissions from the manufacture of buildings the entity acquires or constructs as fixed assets. For a developer, this is the embodied carbon of every project that came on balance sheet during the reporting period. For a REIT, it is acquisitions and major refurbishments.

Category 11 (use of sold products). Emissions from the operational energy use of buildings sold to a buyer. A developer that builds and sells gets hit here over the assumed useful life of the asset.

There is judgement in both. AASB S2 paragraph B40 lets you exclude categories that are not material, but you have to explain the exclusion and the test you applied. "We don't have the data" is not the test. The ASIC RG 280 guidance released in March 2025 made it clear that materiality decisions need to be documented and defensible.

We covered the broader category-by-category logic in our Scope 3 categories explained guide. For property specifically, Category 2 is almost always material if you are doing development work, and Category 11 is almost always material if you sell completed assets.

The spend-based shortcut that creates problems later

The easiest way to put a number on Category 2 is spend-based estimation. Take your annual capex spend on construction. Multiply it by an industry-average emission factor per dollar of construction spend. Call it a number, footnote the method, move on.

It works for a first disclosure. The auditor will sign limited assurance against it in Year 1. The problem starts in Year 2 onwards.

Spend-based estimates have a known accuracy ceiling. The Boston Consulting Group has put the error margin at 30 to 40 per cent. That is fine for a screening exercise. It is not fine for setting a science-based target, for tracking reduction over time, or for the moment your auditor asks why your Category 2 number doubled when your construction spend went up 5 per cent.

Spend-based also has a perverse incentive baked in. Use cheaper inputs and your reported emissions drop. That is the opposite of what the standard intends.

A bottom-up assessment using actual material quantities and product-specific Environmental Product Declarations is more work but produces a number you can stand behind. It also lets you compare across projects in a way spend-based numbers never will. We wrote about why quantity-based beats spend-based in our carbon calculators accuracy piece.

The construction materials side is where this gets messy. Concrete is not one number. A 40 MPa structural mix has roughly double the embodied carbon of a 25 MPa mix, and triple if it uses 0 per cent supplementary cementitious materials. Reinforcing steel from an electric arc furnace looks nothing like steel from a blast furnace. Even AdBlue and form release agents show up in detailed quantity surveys for large projects. Treating "concrete" or "steel" as a single line item throws away most of the precision that makes a bottom-up assessment worth doing. We dug into this in our tier 1 construction materials post.

NABERS Embodied Carbon: the methodology nobody is using yet

NABERS launched Embodied Carbon in late 2024. It is a methodology, not a rating yet, and it covers commercial offices first. Apartments and other building types are on the roadmap.

The methodology is based on EN 15978 (the European standard for life cycle assessment of buildings) and ISO 21930 (the international standard for construction EPDs). It defines what you measure, when in the project lifecycle, and how to handle data gaps. For an Australian REIT or developer, this is the first locally credible methodology that an auditor will recognise without argument.

NABERS Embodied Carbon covers modules A1 to A5 (product stage and construction stage), with optional inclusion of B1 to B5 (use stage embodied) and C1 to C4 (end of life). For AASB S2 Category 2 disclosure, A1 to A5 is the minimum useful boundary.

The link between NABERS Embodied Carbon and AASB S2 is not formal yet. The AASB has not issued specific guidance saying "if you use NABERS Embodied Carbon you have satisfied paragraph 29(a)(i) for Category 2." But practically, having a NABERS-aligned assessment is the strongest defence we have seen against an auditor's "how did you get this number" question.

Green Star Buildings v2: data you already have

If you are a developer or REIT that pursues Green Star Buildings ratings on new projects, you already collect a lot of the data AASB S2 needs.

Green Star v2 requires upfront embodied carbon calculations as part of the Responsible credit. The credit asks for life cycle assessment using product-specific or industry average EPDs, with a 10 per cent reduction from a reference building baseline for a single point. Two points for 20 per cent, three for 40 per cent.

The data sitting in those Green Star submissions, the EPDs collected, the quantity takeoffs, the LCA model, is exactly what feeds Category 2 disclosure. The problem is it usually sits in the sustainability consultant's report and never makes it into the entity's emissions inventory. It gets used for the credit, gets archived, and the embodied carbon number never sees a board paper again.

Pulling that data into the corporate emissions system is the work most developers have not done yet. We have helped property clients do exactly this, taking Green Star data files and structuring them so they roll up into AASB S2 disclosure. The data is there. The plumbing is missing.

The Building Code energy efficiency angle

NCC 2022 raised the operational energy efficiency requirements for new commercial buildings significantly. From 1 October 2023, new Class 5 to 9 buildings must achieve a 7-star NABERS Energy commitment, with whole-of-house energy budgets and more stringent envelope requirements.

This matters for Category 11 disclosure. The use-phase emissions of a building you sell are calculated by multiplying expected operational energy by an assumed grid emission factor across an assumed useful life. NCC 2022 compliance reduces the energy side of that calculation. So does grid decarbonisation over time, which is where assumed grid factors get contentious.

There is no settled Australian convention on whether to hold grid factors flat over a building's 30 to 50 year assumed life, or to use a declining factor based on AEMO's ISP projections. The AASB has not picked one. Most reporters we see use a static current-year factor and disclose it. That is conservative and easier to defend.

The practical workflow for FY26 and FY27 reporting

For a developer or REIT preparing for their first AASB S2 disclosure, the embodied carbon workstream usually breaks down like this:

Step 1: Scope and materiality. Decide which categories are material. Document the test. Category 2 and Category 11 will almost always be in. Categories 4 (upstream transport) and 5 (waste from operations) are often material too. We covered this decision process in Scope 3 emissions reporting mandatory.

Step 2: Year 1 screening estimate. Use spend-based for Category 2 and a simplified operational energy projection for Category 11. This gets you a number for the first disclosure. Be honest in the Basis of Preparation about the method.

Step 3: Project-level bottom-up where it matters. For projects above a materiality threshold (we typically see clients set this at 10,000 sqm GFA or above), do a proper EPD-based LCA. Use NABERS Embodied Carbon methodology if you can. Pull data from Green Star submissions if available.

Step 4: Roll-up into corporate inventory. This is the step that breaks. Project LCAs sit in PDFs. The corporate emissions inventory sits in a spreadsheet or a system. Getting project-level embodied carbon to flow into entity-level Scope 3 Category 2 disclosure requires a data structure that holds material quantities, EPD references, project allocation rules, and ownership percentages (for JV projects).

Step 5: Year 2 onwards: replace estimates with measured data. Each year, more projects have real EPD-based numbers. Spend-based gets used only for the residual. Within three years, you should be running on mostly real data.

This is the workflow our LCA module was built for. It holds EPD references, material quantities by mix and grade, project-level boundaries, and rolls everything up into entity-level Scope 3. For JV projects, the JV consolidation module handles equity-share allocation so each partner reports their portion correctly.

Honest gaps

Three things we will not pretend are solved.

EPD coverage in Australia is still patchy. EPD Australasia has hundreds of certified EPDs, but for some specialised products you still fall back to international EPDs or industry averages. The Carbonly material library prefers Australasian EPDs where they exist and flags when an international or average factor is being used.

Category 11 methodology is unsettled. Grid factor assumptions, useful life assumptions, and whether to include refurbishments over the assumed life all vary between reporters. Until the AASB issues specific property guidance, expect inconsistency across the sector.

Refurbishment vs new build allocation in Category 2 is judgemental. A major refurb where the structure is retained but services are replaced is not a new building, but it is also not a small line item. The boundary between "operational maintenance" (excluded) and "capital works" (Category 2) is where consultants spend a lot of time. Document the boundary you used and stick to it across reporting periods.

What to do this quarter

If you are a Group 2 entity with first disclosure for FY27, the embodied carbon work needs to start now. Pull every Green Star submission your projects have produced in the last three years. Pull capex data by project for FY26 to date. Get a screening estimate done so you know whether Category 2 is going to be 5 per cent or 50 per cent of your total Scope 3.

That single number decides how much effort the rest of the workstream needs.

Embodied Carbon Disclosure for Australian REITs and Developers: What AASB S2 Actually Asks For