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.
