An SBEM calculation is the method Building Control uses to check that a new or altered commercial building meets its carbon emission target under Part L Volume 2 of the Building Regulations – without one, sign-off doesn’t happen. A failing result at Design Stage delays a project before construction starts; a failing result at the As-Built stage can hold up practical completion and the Commercial EPC a sale or lease depends on.
In this guide, you’ll learn:
- What SBEM calculations are and how they differ from SAP
- Which buildings need one, including extensions and change of use
- How the two-stage Design Stage and As-Built process works
- Why air testing has such a direct effect on your result
- What you actually receive at the end: the BRUKL Report and EPC
What Are SBEM Calculations?
SBEM stands for Simplified Building Energy Model – the government-approved methodology used to calculate the energy required to heat, cool, ventilate and light a non-domestic building over a 12-month period. It works by comparing your “Actual Building” against a theoretical “Notional Building” built to the same size and shape but modelled to minimum-compliant specification, to confirm your design meets the carbon emission targets set out in Part L Volume 2 of the Building Regulations – specifically Part L2A for new buildings and Part L2B for existing buildings.
Run early enough, an SBEM calculation is also the cheapest point to catch a problem: adjusting a specification on paper costs far less than fixing it once the building is up.
SBEM vs SAP: What’s the Difference?
SBEM and SAP are both government-approved energy modelling methodologies, but they apply to different building types. SBEM covers non-domestic buildings – offices, retail units, schools, warehouses. SAP (the Standard Assessment Procedure) covers domestic dwellings – houses and flats. A mixed-use development typically needs both: SAP calculations for the residential units, SBEM calculations for any commercial space.
Which Buildings Need a Commercial SBEM Calculation?
Almost all new non-domestic buildings need one, spanning commercial (offices, retail, warehouses), public sector (schools, universities, hospitals, care homes), industrial (factories, workshops) and leisure (hotels, gyms, recreation centres).
Existing buildings need one too, if the project involves:
- An extension
- A change of use (a barn converted to an office, for example)
- A refurbishment that changes a “thermal element” – HVAC, windows or insulation
Unheated buildings and places of worship are often exempt.
When Are SBEM Calculations Carried Out?
SBEM isn’t a single event – it’s a two-stage process required for sign-off:
- Design Stage (pre-construction): submitted to Building Control before work begins, proving that the building will pass if built to the proposed specification. This is the point at which it’s cheapest to test different insulation or heating options against the target.
- As-Built Stage (completion): the calculation is updated with whatever actually changed during the build, generating the final BRUKL Report and the Energy Performance Certificate.
SBEM Certificates, BRUKL Reports and EPCs: What You Actually Get
SBEM itself is a calculation methodology, not a certificate – so “SBEM certificate” is usually shorthand for one of two actual documents. The BRUKL Report is the technical output of the calculation: a Design Stage BRUKL is submitted to Building Control before construction to prove the design works, and an As-Built BRUKL is submitted after construction to prove the building was actually built to that specification. The Commercial EPC is generated directly from the completed As-Built calculation, grading the building A+ to G on the certificate that Building Control, tenants and buyers actually see – and that’s legally required to sell, let or lease a commercial property.
Why Air Testing Has Such a Direct Effect on Your SBEM Result
At the As-Built stage, we strongly recommend an air permeability test. Without one, the SBEM software forces your assessor to use a default air leakage figure – typically 15 to 25 m³/hr/m², representing a genuinely leaky building. A well-insulated building can still fail its compliance check simply because it wasn’t tested, since a measured result usually comes in well above that punitive default.
We’ve seen exactly this play out for two Bristol commercial clients, where replacing a default air permeability assumption with a real test result was the difference between a failing rating and a compliant one:
Getting Started: The SBEM Process
An SBEM calculation is carried out by an accredited Level 4 or Level 5 Energy Assessor, working from your drawings and specifications through to a certified BRUKL Report. For a full walkthrough of what that process actually involves – from initial review to certification – see our SBEM Assessment guide.
What’s Next?
Whether you’re at Design Stage on a new commercial build or facing a change-of-use assessment on an existing one, getting the SBEM calculation right early keeps a build programme moving rather than stalling it at sign-off.
We carry out SBEM calculations at both Design Stage and As-Built for new-build, extension, change-of-use and shell-and-core-to-fit-out projects across the South West and nationwide.
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