SBEM calculations and BRUKL reports explained

What SBEM does

SBEM — the Simplified Building Energy Model — is the standard tool for demonstrating non-domestic Part L compliance. It divides a building into zones, assigns an activity to each zone from a standard set, and models the fabric, heating, cooling, ventilation, lighting and hot water serving those zones. From that it produces the Building Emission Rate and Building Primary Energy Rate, and compares them against targets derived from a notional building of the same geometry. The compliance output is the BRUKL report, which is what building control reads.

SBEM or dynamic simulation?

SBEM handles the majority of buildings well. Dynamic simulation modelling becomes the better route where the building's behaviour over time genuinely matters — significant solar gain, complex mixed-mode ventilation, atria, or where the same model is being used for overheating and comfort work as well as compliance. Approved dynamic simulation software is equally valid under the National Calculation Methodology; the choice is about fitting the tool to the building, not about finding a softer test.

Zoning and activities: where results are really decided

In non-domestic modelling, the geometry and the activity assignments carry enormous weight. A floor split into the wrong zones, an office modelled as a warehouse, or a plant room treated as conditioned space will move the result far more than a marginal change in wall U-value. Good practice is to agree the zoning approach with the design team early and to keep it aligned with the mechanical and electrical layouts, so the model reflects how the building will actually be operated.

Shell and core, fit-out, and change of use

Non-domestic work rarely arrives as a clean new-build. A shell-and-core building is assessed on what the landlord is providing, with assumptions recorded for the tenant's fit-out; the fit-out itself is then a separate piece of work. A change of use — offices to residential, retail to a gym — can pull a building into a different set of requirements entirely, and mixed-use schemes may need both SAP for the dwellings and SBEM for the commercial parts, reconciled so that shared systems are not counted twice or missed.

• New build: full design-stage and as-built BRUKL
• Shell and core: landlord provision modelled, tenant assumptions recorded
• Fit-out: assessed against the base-build assumptions
• Extensions to non-domestic buildings: assessed on the new work
• Change of use: check which requirements the new use triggers
• Mixed-use: SAP for dwellings and SBEM for commercial, reconciled across shared systems

Design stage and as-built

The pattern mirrors dwellings. A design-stage BRUKL goes to the building control body so that any shortfall is found while it is still a drawing change. At completion the model is re-run against what was installed, supported by commissioning records for the fixed building services and the site evidence your building control body asks for. On non-domestic schemes the commissioning paperwork is usually the long pole — it is worth naming who owns it at the start of the job.

What we need to model your building

For a fee we can stand behind, we need enough to build the geometry and the systems. That is normally the architectural drawings, the mechanical and electrical strategy, and a note of any planning energy condition. If the M&E design is not fixed, we can model the design intent and flag the assumptions in writing rather than guess quietly.