A life cycle assessment sets out to answer a reasonable question: what is a building’s environmental impact, measured across its whole life rather than just the materials list. The method traces a building or a product from raw material extraction through manufacture, transport, construction, occupation and eventual demolition, which returns a figure.
A life cycle assessment is one of the most rigorous instruments the construction industry has for comparing the impact of one building against another, and the same building can return very different numbers depending on where the assessor draws the boundary, as in the data that’s fed in, and what’s assumed about a future that hasn’t happened yet. The number is only as trustworthy as the disclosure of what went into it.
What a life cycle assessment measures
Two standards do the heavy lifting work when it comes to life cycle assessments. ISO 14040 and 14044 set the principles and the method for life cycle assessment across any product. EN 15978 applies that method at the scale of a whole building, and it is the framework that Australian and New Zealand practice has largely adopted, particularly where an assessment has to line up with Green Star or NABERS.
EN 15978 divides a building’s life into stages, each labelled. The product stage covers raw material extraction, transport to the factory and manufacture (A1 to A3). The construction stage covers transport to site and installation (A4 and A5). The use stage covers everything that happens while the building stands: maintenance, repair, replacement, refurbishment, and the operational energy and water the building consumes (B1 to B7). The end-of-life stage covers demolition, transport, waste processing and disposal (C1 to C4). A separate module, D, records the benefits of recycling or reuse beyond the building’s life.
Upfront carbon means A1 to A5: everything emitted before anyone moves in. Embodied carbon covers the materials across their life, the product and construction stages, plus maintenance, replacement and end of life, but not the energy used to run the building.
Operational carbon is that running energy, B6 and B7. Whole-of-life carbon is the lot. A figure quoted as a building’s carbon can mean any of these.
Another basic concept of a life cycle assessment is the idea of “cradle-to-grave”, or the revised concept of “cradle-to-cradle” analysis, which takes into account all inputs and outputs associated with a product from its inception to its final disposal. This holistic approach allows for a comprehensive understanding of not only direct environmental impacts but also indirect consequences that may arise at different stages of the product’s life cycle.
Where the number moves
Three decisions shift an LCA result before the building itself changes at all.
The first is the boundary. A cradle-to-gate assessment stops at the factory door (A1 to A3). An upfront assessment runs to practical completion (A1 to A5). A cradle-to-grave assessment carries through to demolition (A1 to C4). Each is legitimate, but they assess carbon at different levels. Two buildings can only be compared when matched like for like.
An assessment is only as good as the environmental data behind each material. A project-specific Environmental Product Declaration (EPD), verified for the actual product specified, gives a precise, traceable figure. Where no declaration exists, and for many specialist products in Australia none does, the assessor falls back on industry averages from a database such as EPiC, and the result loses its specificity. The same wall, modelled with generic data or with a manufacturer’s verified declaration, returns two different numbers.
The third is the set of assumptions about the future. Use-stage figures depend on a reference study period, conventionally fifty or sixty years, and on predictions about how often components get replaced, how fast the electricity grid decarbonises across those decades, and what happens to the materials at end of life. These are forecasts. A building assessed against an optimistic grid curve reports lower operational emissions than the same building assessed against a conservative one, and neither assessor has done anything improper.
Biogenic carbon is something else to consider. Concrete and steel carry high, fairly settled embodied figures; timber is a material the accounting fights over. Timber stores carbon drawn down while the tree grew, and an assessment can record that storage as a benefit at the product stage or as a debt released at end of life, depending on the approach chosen. The choice can swing a timber building’s result substantially. That variability is not a scandal to be hidden. It is the nature of a modelled estimate.
The regulation is being standardised
Changes are happening across Australia. In November 2024, NABERS launched an Embodied Carbon rating. It measures upfront carbon, A1 to A5, requires a verified Bill of Quantities, and pushes assessors toward product-specific declarations over default factors. Updated in February 2026, it is the closest thing Australia has to a common yardstick, and its designers expect embodied carbon to become the largest source of built-environment emissions as operational energy cleans up.
The National Construction Code 2025, published in February 2026 and available for state adoption from May, introduces a voluntary pathway for reporting embodied carbon in commercial buildings, and recommends the NABERS method to do it. Voluntary is the operative word: mandatory embodied-carbon provisions are widely expected at the next code cycle, around 2028. New South Wales has already moved further, requiring embodied-carbon reporting for new residential development through the BASIX Materials Index since October 2023, and for non-residential buildings through the Sustainable Buildings SEPP. Green Star Buildings v1.1, mandatory for new project registrations from May 2026, aligns its embodied-carbon reporting with NABERS as well.
Underneath all of it sits mandatory climate reporting, phased in from 2025, which requires large entities to disclose emissions including the Scope 3 emissions embedded in their supply chains. In construction that reaches the material manufacturers and the volume builders first, and the disclosure data will flow downstream regardless of whether a given architect asked for it. A practice that has never run an assessment will shortly be handed supplier figures that it has to make sense of.
The reasonable objection to all of this is that dwelling on uncertainty is a delay tactic, and that an imperfect number beats no number. Standardisation is doing exactly what it should: NABERS is about fixing the limit of upfront carbon and demanding a verified Bill of Quantities removes most of the discretion that made early assessments unquotable, much as operational-energy ratings were disciplined two decades ago. The tool is improving, and the direction is set.
A certified upfront rating is a genuine, verified figure for A1 to A5. It is not a whole-of-life figure, but the reuse case makes for a compelling story. The largest embodied-carbon saving available to most projects is not building at all, and the benefit of keeping an existing structure often lands in Module D, reported separately from the headline.
What an assessment can't tell you
A life cycle assessment cannot verify its own forecasts. A whole-of-life figure rests on fifty or sixty years of predictions about replacement, grid supply and demolition, and no one confirms them until long after the decisions they informed have been made. Biogenic carbon accounting remains genuinely unsettled, not merely inconsistent. Declaration coverage for Australian products is patchy, so many assessments still run partly on averages. And a comparison between two buildings when their functional equivalent and limits are identical.
None of this argues against doing the assessment. It means reading the result as a fact rather than as a modelled estimate with a scope attached.
The number is only as good as its boundary
A life cycle assessment is worth doing, and worth trusting, on one condition: that the figure arrives with the boundary, the data basis and the assumptions that produced it. Stripped of those, an LCA number is a marketing figure wearing the authority of a measurement. The regulation now moving through Australian practice is slowly making the scope legible, which is the real work. Until it is finished, the useful question about any building’s environmental number is what it actually counts.
Common questions
What does a life cycle assessment measure? It measures the environmental impact of a building or product across its life, from raw material extraction through manufacture, transport, construction, use and demolition, following ISO 14040 and 14044 and, at building scale, EN 15978. The result is usually reported as embodied, operational or whole-of-life carbon, and the three are different figures.
What is the difference between embodied and operational carbon? Operational carbon is the emissions from running a building: heating, cooling, lighting and water. Embodied carbon is the emissions locked into its materials, across extraction, manufacture, transport, construction, maintenance and end of life. As grids decarbonise, embodied carbon becomes the larger share of a new building’s whole-of-life emissions.
Is a life cycle assessment required for buildings in Australia? It depends on the building and the state. Nationally, the National Construction Code 2025 makes embodied-carbon reporting voluntary for commercial buildings, with mandatory provisions expected around 2028. New South Wales already requires it for new residential development through the BASIX Materials Index and for non-residential buildings through the Sustainable Buildings SEPP. NABERS and Green Star Buildings provide the assessment methods.
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