Sustainability
Part L compliance modelling, England and Wales
Non-domestic Part L compliance modelling and BRUKL reporting at design and as-built stage, run early enough to change the design rather than to report on it.
- Discipline
- Sustainability
WHAT IT IS
Part L of the Approved Documents covers conservation of fuel and power. For a non-domestic building, compliance is demonstrated by modelling the building against a notional equivalent under the National Calculation Methodology, in SBEM or in an approved dynamic simulation model.
The output is the BRUKL report — Building Regulations UK Part L — which sets out the building's calculated emission rate and primary energy rate against their targets, together with the minimum fabric and services standards the design has to meet regardless of the overall result.
Compliance is demonstrated twice: once at design stage, and again as built, with the commissioning and air permeability evidence to support it.
WHEN YOU NEED IT
At Stage 2 or 3 for the design-stage submission, and again before completion for the as-built report.
The second one is where projects come unstuck. The design-stage BRUKL commits the building to a set of specific efficiencies, specific fan powers, control functions and an air permeability figure. If any of them is substituted on site without being re-checked, the as-built model fails and the building cannot be signed off until it is resolved — usually at the least convenient moment in the programme.
OUR PROCESS
Design stage
Model built while the fabric, glazing and heat source are still open, run against the options, and issued with a written schedule of what it commits the design to.
Through construction
Contractor substitutions checked against that schedule as they are proposed rather than as they are discovered. A pump or an AHU with a different specific fan power is a compliance question, not just a procurement one.
As built
As-built model updated to the installed equipment, with commissioning records and the air permeability test result, and the as-built BRUKL issued for completion.
DELIVERABLES
What you receive
- Design-stage SBEM or dynamic simulation model
- Design-stage BRUKL report
- Schedule of the inputs the model commits the design to
- Substitution checks through construction
- As-built model and as-built BRUKL report
STANDARDS
Standards applied
The editions in force at the time of design. Where a standard is amended mid-project we confirm which edition the appointment is based on.
- Approved Document L Volume 2Conservation of fuel and power — buildings other than dwellings (England)GOV.UK
- Approved Document L (Wales)Conservation of fuel and power — Welsh editionGOV.UK
- NCM Modelling GuideNational Calculation Methodology, non-domesticBRE / NCM
- CIBSE TM54Evaluating operational energy use at the design stageCIBSE
- CIBSE Commissioning CodesSeriesCIBSE
QUESTIONS
Common questions
What is a BRUKL report?
BRUKL stands for Building Regulations UK Part L. It is the output document produced by approved Part L compliance software for a non-domestic building, showing the calculated building emission rate and primary energy rate against their targets, whether each minimum fabric and services standard is met, and the assumptions the calculation relied on. Building control expects one at design stage and one as built.
Why did my building fail Part L?
Most non-domestic failures come from one of four things: glazing area above what the fabric and shading can carry, a heat source with worse carbon performance than the notional building assumes, specific fan powers or distribution losses above the modelled values, or a minimum standard missed on an individual element even though the overall target is met. The model will identify which, and the fix is much cheaper before spatial coordination than after it.
Is Part L compliance modelling a prediction of energy use?
No. Part L modelling compares the building against a notional equivalent using standardised occupancy, operating hours and internal gains. It demonstrates compliance and nothing more. Predicting actual consumption is a separate exercise with a separate methodology, CIBSE TM54, and the gap between the two is routinely large enough to matter to a client planning around running costs.
What happens if equipment is substituted during construction?
The as-built model has to reflect what was actually installed, so any substitution that changes an efficiency, a specific fan power, a control function or the air permeability result changes the compliance position. Checking a proposed substitution against the design-stage model takes a few minutes; discovering it at the as-built stage can hold up completion.