Approved Document L Volume 2 (Buildings other than dwellings) was revised in December 2021 and came into force for new building control applications submitted from 15 June 2022. It is the biggest single tightening of commercial Part L compliance since 2013, with a 27% reduction in CO₂ emissions versus the 2013 baseline and the introduction of the primary energy metric.
Despite that, the underlying mechanics — SBEM and BRUKL — work the same way they always have. Here's what developers, project managers and architects need to know before commissioning the assessment.
SBEM and BRUKL: what they actually are
SBEM (Simplified Building Energy Model) is the government-approved calculation methodology that proves a non-domestic building meets Part L. It models the building against a notional reference building of the same shape and size built to the Part L baseline, and compares CO₂ emissions, fabric performance and primary energy use.
BRUKL (Building Regulations UK Part L) is the standardised output report SBEM produces. It's what building control reads to decide whether the building passes. You can't have one without the other; SBEM is the engine, BRUKL is the printout.
Complex buildings with atria, displacement ventilation or extensive natural ventilation may need DSM (Dynamic Simulation Modelling) instead of SBEM, using software like IES VE or DesignBuilder. Most commercial schemes don't, and stick with SBEM throughout.
What changed in 2021
Three things matter most. First, the headline 27% CO₂ reduction target for new non-domestic buildings against the 2013 baseline. Second, the introduction of primary energy as a metric in addition to CO₂, recognising that grid decarbonisation has changed the relative footprint of fuels. Third, tighter limiting values for U-values, air permeability and thermal bridging.
On the services side, fixed building services (FBS) get a tighter set of efficiency floors, lighting must hit at least 95 luminaire lumens per circuit watt across the average installation, and heat pumps are now the default assumption for the notional building's heating. That last point matters: a gas-fired heating system in a new commercial building now has to claw back the CO₂ disadvantage somewhere else in the design.
When you need a BRUKL: design stage and as-built
Two BRUKLs are required on every Part L commercial project. The design-stage BRUKL is submitted with the building control application to prove the design will comply. The as-built BRUKL is produced near practical completion using actual installed specifications, and is mandatory before building control will sign off the project.
Don't skip straight to the as-built. The design-stage BRUKL is your insurance policy: if it passes, the design is signed off, and any deviations during construction are easy to flag and fix. If you only model at the end, every spec change made during construction has to be caught up after the fact, often with expensive remedial work.
What an assessor needs from you
Provide architectural plans showing accurate dimensions, glazing percentages, ceiling heights and zone boundaries. Provide the M&E specifications for HVAC, lighting and DHW including efficiency ratings and control strategies. Provide U-value calculations for each thermal element with build-up details. Provide the air-permeability target you're designing to.
If you can also share the structural section drawings for thermal bridging detail and the proposed BMS schematic, the model is materially more accurate. Vague briefs lead to default values being used, which usually understate efficiency and push the building into the 'fail' camp at design stage.
Cat A and Cat B fit-outs: yes, you need a separate BRUKL
A common assumption is that the shell-and-core BRUKL covers any subsequent fit-out. It doesn't. Most Cat A and Cat B fit-outs install or replace controlled services (heating, cooling, ventilation, lighting), and any of those triggers the Building Regulations independently of the base build.
The fit-out's own BRUKL doesn't have to re-prove the shell; it has to demonstrate that the fit-out's services and any added partitioning still meet Part L. This is usually a smaller, simpler model than the original shell-and-core, but it's a separate piece of work with its own building control submission.
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