Part L 2021: what changed and what it means for design teams
The 2021 uplift to Part L is the biggest tightening of building fabric and services requirements in a decade. A working summary for architects and developers.
3 Jul 20263 min read
Part L 2021: what changed and what it means for design teams
The 2021 update to Approved Document L introduced a 27% reduction in carbon emissions for new non-domestic buildings and set the direction of travel toward the Future Buildings Standard.
Headline changes
- ›Notional building spec now assumes better fabric U-values, PV, and heat pumps as standard.
- ›BER/TER gap requires designs to be genuinely well-optimised — you can no longer rely on trading off poor fabric against efficient services.
- ›As-built proof through commissioning evidence, TER/BER reporting and the Building Regulations England Part L2 (BREL) report.
What design teams should do differently
Early-stage SBEM modelling is now essential. Retrofit-fitting compliance at Stage 4 typically means re-designing the services strategy, glazing ratio, or fabric spec — expensive and slow.
Our Part L / SBEM team engages at RIBA Stage 2 to model options, so the compliant design is also the design you want to build.