Life Cycle Assessment – Similar buildings approach (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. Where all buildings are demonstrably identical in design and specification (and differ only in scale), a representative LCA approach may be used (see
KBCN1890).
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.
09.07.2026 Reference to KBCN1890 added
Life Cycle Assessment – Similar buildings with identical design (GN20 Section 4) – Representative LCA approach - KBCN1890
Where multiple buildings are substantially identical in design, construction and specification, and any differences are limited to scale, a representative LCA approach may be used instead of completing a full LCA for every building.
Where buildings are not substantially identical, see
KBCN1834.
For the purposes of BREEAM benchmarking under Mat01:
- A representative LCA and a single options appraisal may be applied across all buildings, provided that all specifications (including scoped elements) are consistent and carbon reduction measures are specification-driven rather than scale-dependent.
- Robust justification and supporting evidence must be provided to confirm representativeness. The representative model should normally be the largest, most carbon-intensive, or otherwise demonstrably representative building within the development.
- Results must be expressed in normalised form (e.g. kgCO₂e/m²) and demonstrated to be applicable across all units, with any variation in outcomes shown to be not materially significant (e.g. within ±10%).
- 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.
Demonstrating representativeness does not require full LCAs for additional units; proportionate methods such as parametric scaling of quantities or elemental intensity comparisons may be used to evidence that variation in normalised results is not materially significant. Where there is uncertainty regarding representativeness, a secondary check model for an additional unit is recommended to verify consistency of results.
Rationale: The representative LCA approach provides a proportionate means of assessing developments containing multiple highly similar buildings while maintaining confidence that reported results are representative of individual building performance. It is intended as a limited exception to the standard requirement for building-specific assessment.
Information correct as of 9