SBEM calculations from £150

SBEM is the approved methodology for showing that a new or substantially altered non-domestic building complies with Part L of the Building Regulations, in the same way SAP applies to dwellings. The output is a BRUKL report, comparing the building's calculated emissions against a notional target building of the same size, shape and use, which building control requires before signing off the works. Without a satisfactory BRUKL report, a non-domestic building cannot progress to completion sign-off, regardless of how the construction itself has gone.

Anyone constructing a new non-domestic building, or carrying out works that trigger a Part L assessment, needs an SBEM calculation.

A non-domestic building rarely has a single uniform use, and SBEM results depend heavily on how the building is divided into zones, each carrying its own activity type, occupancy pattern and servicing strategy. Treating a mixed-use building — retail at ground floor, offices above, for instance — as a single zone produces an inaccurate result, sometimes favourably, sometimes not, and either way not one that reflects the building as it will actually operate. We zone the model to match the real design intent floor by floor and area by area.

A reliable SBEM model needs scaled drawings showing the building's layout and intended zoning, glazing specification per elevation, the HVAC system type and efficiency for each zone, lighting specification including any controls, and details of any mechanical ventilation with heat recovery. The earlier this specification is settled, the more useful the model is at guiding design decisions rather than simply confirming a result after the fact.

SBEM is most valuable when run iteratively through the design process — at concept, at planning, and again at technical design — rather than as a single check once drawings are finished. An early model shows which elements are driving the compliance margin while there is still time to adjust glazing, controls or HVAC selection cheaply, rather than discovering a shortfall once specification and pricing decisions have already been made.

Pricing depends on the building's size, how many zones it needs, and the complexity of its services — a small single-zone unit is far simpler to model than a large, heavily serviced multi-let office. Interim design-stage checks are priced separately from the final compliance submission, and multi-unit developments benefit from a reduced rate once a template has been established.

A straightforward single-zone model can usually be turned around within a working week of receiving a complete specification; larger, more heavily zoned buildings take longer to model accurately. Where a scheme needs adjustment to pass, we identify the lowest-cost changes and re-run the model quickly so a revised BRUKL report can be issued without a lengthy delay to the building control submission.

The most frequent cause of an initial shortfall is an HVAC specification chosen before the compliance calculation was run, followed by glazing selected for appearance without checking the associated heat loss, and lighting without occupancy or daylight controls. Rather than defaulting to the most expensive fix, we identify which combination of adjustments — usually lighting controls, airtightness, or glazing performance — closes the gap at the lowest overall cost.

We model buildings zone by zone to reflect real design intent, run interim checks early enough in the design process to matter, and produce the BRUKL report building control needs alongside clear, cost-ranked advice if a scheme needs adjusting.

The Simplified Building Energy Model, SBEM, is the approved methodology for demonstrating Part L compliance in most new and substantially altered non-domestic buildings, in the same way SAP applies to dwellings. Running the model produces a BRUKL output document — Building Regulations UK Part L — which is the formal compliance report submitted to building control, setting out the building's calculated emissions against its target, along with a summary of the specification the model was built from. The BRUKL report is a public-facing summary rather than the underlying model file itself, which is why it needs to be checked for accuracy on its own terms: an error in how a zone was described in the model can produce a BRUKL output that looks compliant on the surface while resting on an unrealistic assumption underneath.

As with the domestic methodology, non-domestic Part L compliance under the 2021 uplift is demonstrated against a notional building of the same size, shape and use, generating a Target Emission Rate that the actual Building Emission Rate must not exceed, alongside separate fabric performance backstops for U-values and airtightness that apply regardless of how the overall emissions calculation comes out. This means a building cannot simply compensate for poor fabric with efficient services and call itself compliant; certain minimum fabric standards have to be met in their own right. We check both the headline emissions comparison and the backstop values individually, since a scheme can pass on the headline figure while still needing individual elements corrected to satisfy the backstops.

SBEM results are most sensitive to how the building is zoned, since each zone carries its own activity type, occupancy pattern and servicing strategy, and an oversimplified zoning model — treating a building with mixed retail and office use as a single zone, for example — can produce a materially inaccurate result in either direction. Beyond zoning, the model is heavily influenced by glazing ratio and specification, HVAC system type and efficiency, lighting power density and controls such as daylight and occupancy sensing, and the specification of any mechanical ventilation with heat recovery. We build the model to reflect the actual design intent zone by zone rather than applying a single blended specification across the whole building, because that is where most of the inaccuracy in poorly produced SBEM models originates.

The most frequent cause of an SBEM scheme initially failing is an HVAC specification that was priced and selected before the compliance calculation was run, leaving little room to adjust once the model shows a shortfall. Others include glazing specified for daylighting or aesthetics without checking the associated solar gain and heat loss penalty, and lighting schemes specified without occupancy or daylight controls that the model needs in order to credit a lower power density. Where a scheme falls short, the most cost-effective fixes are usually improving lighting controls and specification, tightening airtightness where the design allows it economically, and adjusting glazing performance rather than replacing the HVAC system outright, which is typically the most expensive and disruptive lever to pull. We identify which combination of adjustments closes the gap at the lowest overall cost rather than defaulting to the most obvious single change.

SBEM produces the most useful result when it is run iteratively alongside the design process rather than as a single check once drawings are finished. Running an early model from an outline specification lets the design team see which elements are driving the compliance margin while there is still time to adjust glazing, controls or HVAC selection without a costly late-stage redesign. We provide interim modelling at key design stages — concept, planning, and technical design — so the final compliance submission is confirming a result the design team already expected, rather than surfacing a problem for the first time when it is expensive to fix.