Embodied Carbon Explainer
Understanding how Embodied Carbon fits within the tools
Key takeaway
Embodied carbon is now a core part of building assessment. Below we outline how it is typically measured in Australia, how upfront carbon differs from a full Life Cycle Assessment (LCA), how Green Building Council of Australia (GBCA) approaches Credit 24 in Green Star Buildings v1.1, and how NABERS and LCA compare in scope and cost.
Frameworks
Life Cycle Assessments are comparative assessments whereby a ‘Proposed design’ is compared against a ‘Business-As-Usual’ design across a number of impact categories and across the Materials and Construction Stage (A1 - A5), Use Stage (B1 - B7), End of Life Stage (C1 - C4) and Benefits & Loads beyond the System Boundary (Module D).
When considering LCAs, there are two common approaches to developing a ‘Business-as-Usual’ case:
Reference building approach
The proposed design is compared to a project-defined “reference” building. Performance is expressed as a percentage improvement against that baseline. This method allows for tailored comparison but requires clearly defined and defensible assumptions.
Benchmark approach
The building’s upfront embodied carbon intensity (e.g. kgCO₂-e/m²) is compared against an external benchmark or target. This improves cross-project comparability and reduces debate about baseline modelling assumptions.
Embodied Carbon Boundaries: Upfront vs Full Life Cycle
Upfront embodied carbon (A1–A5) captures emissions from material extraction, manufacturing, transport and construction. These impacts are largely “locked in” once procurement decisions are made, making them highly actionable during design. Selection of EPD certified products and optimisation of transportation logistics are paramount to reductions.
Key optimisations include: improved selection of Carpets, Engineered Timber, Acoustic Panels and Plasterboard.
A full Life Cycle Assessment (LCA) extends beyond upfront impacts to include maintenance and replacement (B stages), end-of-life (C stages), and sometimes benefits beyond the boundary (D stage). Upfront carbon is therefore a subset of whole-of-life LCA. Operational energy is typically a major contributor to overall reductions, and therefore is an important consideration.
Key optimisations include: improved operational energy and enhanced material selections.
Upfront Embodied Carbon analysis drives immediate reductions. Whole-of-life LCA ensures optimisation does not shift impacts to later stages.
Green Star Buildings v1.1 – Credit 24 (Upfront Carbon Reduction)
Under Green Star Buildings v1.1, projects can pursue three pathways:
Pathway A – Benchmark
Demonstrate upfront carbon is at least 10% below the published benchmark.
Pathway B – Reference Building
Show at least 10% lower upfront carbon than a defined reference building (via calculator or comparative LCA).
Pathway C – NABERS Embodied Carbon
Use a NABERS Embodied Carbon rating as an alternative benchmark pathway.
An additional point is available under Credit 10 (Impacts Disclosure) for disclosure of a whole-of-building, whole-of-life LCA.
If a full LCA is already being completed, it is efficient to use the same model to demonstrate Credit 24 Pathway B by running a proposed vs reference comparison for A1–A5.
NABERS Embodied Carbon vs Detailed LCA – Scope and Cost
NABERS Embodied Carbon
Scope: Focuses on upfront embodied carbon (A1–A5).
Purpose: Benchmarking, target-setting, portfolio comparison and credible disclosure.
Methodology: Standardised rules and verification process.
Cost profile: Typically moderate and predictable, reflecting defined boundaries and streamlined modelling.
Detailed LCA (eTool, One Click LCA or equivalent)
Scope: Can include upfront (A1–A5) or full life cycle (A–D).
Purpose: Design optimisation, hotspot identification, scenario testing and strategic material selection.
Methodology: Iterative modelling using detailed quantities and EPD data.
Cost profile: Higher than NABERS modelling due to broader scope, iterative analysis and data intensity. Costs vary depending on project scale and design phase engagement.
In practice, NABERS provides a consistent and externally benchmarked reporting framework, while LCA enables deeper technical interrogation and carbon reduction. Used together, they support both credible disclosure and measurable impact reduction.
What We’ve Learnt
Benchmark pathways (Green Star Pathway A and NABERS) improve comparability and reduce debate around baseline assumptions.
Whole-of-life LCAs unlock additional Green Star points and provide stronger ESG narratives.
Early hotspot analysis delivers the largest carbon reduction gains.
Project LCAs can be structured to support Scope 3 accounting, with consistent quantities and emission-factor evidence forming an auditable basis for organisational climate reporting.
