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Mat 01 - Building life cycle assessment
Information correct as of 19thApril 2026. Please see kb.breeam.com for the latest compliance information.
Clarification of ‘Embodied carbon benchmark comparison’ - KBCN1819
The
embodied carbon benchmark comparison must always be based on the
latest appropriate LCA stage that corresponds to the BREEAM assessment stage being pursued.
The purpose of the benchmark comparison is to assess
outcome-based embodied carbon performance, using data that is representative of the building at the relevant assessment stage.
Assessment stage requirements
Interim (Design Stage) BREEAM assessments
- Where an interim / design stage assessment is being submitted:
- The benchmark comparison may be based on a Technical Design LCA, where this represents the latest LCA available at that stage.
- Benchmark results at this stage are indicative and intended to support design decision-making.
Final Post-Construction Stage (PCS) BREEAM assessments
- Where a final post-construction stage (PCS) assessment is being submitted:
- Benchmark comparison credits can only be awarded where a Post-Construction Stage (PCS) LCA has been completed.
- A technical design LCA alone is not sufficient to support benchmark comparison credits at PCS.
- This is because the PCS LCA is the only assessment that reflects the materials and products actually installed in the completed building, and therefore the only suitable basis for outcome-based benchmarking.
If a PCS LCA is
not undertaken, benchmark comparison credits
cannot be awarded at final assessment, regardless of whether a technical design LCA was previously completed.
This aligns with wider industry frameworks (e.g. RICS WLCA v2 and the UK Net Zero Carbon Buildings Standard), which anchor performance claims to as-built outcomes.
Independent third party – clarification on the definition - KBCN1805
For the purposes of BREEAM, sister companies or parent companies cannot be considered as third parties. To be classed as an independent third party, there must be no professional connection or relationship between the LCA consultant/energy assessor, or their company, and the verification body.
The third-party verifier must be independent of the LCA or energy assessor and demonstrate impartiality (for general principles, see ISO 17029). To qualify as a third party, the verifier must belong to an organisation not involved in the project and must not provide advice to the project, as this could compromise their impartiality during verification.
Life Cycle Assessment for multiple buildings within a single assessment (GN20 – Section 6) - KBCN1835
Where a BREEAM assessment includes multiple buildings on the same site with a single, over-arching function, in accordance with Section 6 of GN20 (e.g. a principal building with one or more ancillary or supporting buildings), and where these are not classified as ‘similar buildings’,
each building must be assessed and reported separately within the LCA.
A single aggregated result for the whole site is
not sufficient on its own, even where a single coordinated LCA model is used.
Shared elements (e.g. substructure, external works, or building services serving multiple buildings) may be
apportioned between buildings using a reasonable and transparent method (e.g. by gross internal area or other appropriate project-specific metric), in line with recognised industry approaches.
For the purposes of BREEAM benchmarking under Mat 01:
• The results submitted to the platform must represent
a single building, not a combined site-wide result.
• Where multiple buildings are included within an assessment, benchmarking (in kgCO₂e/m²) must be based on the
principal building. Where no clear principal building exists, the largest building should be used.
Full evidence must be provided to demonstrate:
• That all buildings within scope are included,
with individual LCAs completed for each building, and
• How results have been separated and, where relevant, how shared elements have been allocated.
Rationale:
Industry standards such as RICS guidance and the UK Net Zero Carbon Buildings Standard define assessment boundaries at the building (asset) level, while allowing aggregation at project level only where individual building results are also reported.
Requiring building-level results ensures consistency with industry practice, maintains comparability with BREEAM benchmarks, and avoids distortion where multiple buildings are combined into a single result.
Note: This approach applies until further platform functionality is available to support multi-building submissions directly.
Life Cycle Assessment where similar buildings approach is being followed (GN20 – Section 4) - KBCN1834
Where multiple buildings are included within the scope of a single BREEAM assessment following the Similar Buildings approach, in accordance with Section 4 of GN20, unless identical, each building must be assessed and reported separately within the LCA.
Shared elements (e.g. substructure, external works, or building services serving multiple buildings) may be apportioned between buildings using a reasonable and transparent method (e.g. by gross internal area or other appropriate project-specific metric), in line with recognised industry approaches.
For the purposes of BREEAM benchmarking under Mat 01:
• The results submitted to the platform must represent a single building, not a combined site-wide result.
• Where multiple buildings are included within an assessment, the worst-performing building (in kgCO₂e/m²) must be used for benchmarking in line with the Similar Buildings methodology (section 4.2 of GN20).
Full evidence must be provided to demonstrate:
• That all buildings within scope of the assessment have been included, with individual LCAs completed for each building, and
• How results have been separated and, where relevant, how shared elements have been allocated.
Rationale: In line with Section 4.2 of GN20, BREEAM issues must be assessed for each individual building, with credits awarded based on the worst‑performing building for each assessment issue. The Similar Buildings approach therefore remains an individual‑building assessment methodology and does not constitute a site‑wide assessment, even where multiple buildings are included.
Information correct as of 19thApril 2026. Please see kb.breeam.com for the latest compliance information.