An SBEM assessment is the government approved calculation used to prove that a building other than a dwelling complies with Part L of the Building Regulations. It compares your building against a notional building of the same size and shape built to a fixed specification and produces the BRUKL report your building control body needs.

Watch by section

• [0:00] Introduction
• [0:37] What is an SBEM
• [0:50] How is it completed
• [1:42] When is an SBEM required
• [2:34] Difference between SAP and SBEM
• [3:26] Required information to complete an SBEM assessment
• [4:39] Information you receive to submit to building control

What is an SBEM assessment?

SBEM stands for Simplified Building Energy Model. It is the government approved method for calculating the energy performance of any building that is not a home. The same calculation produces two things: the BRUKL report used to demonstrate Part L compliance, and the non-domestic Energy Performance Certificate.

SBEM sits within the National Calculation Methodology, which sets the calculation rules and the standard databases every assessor has to use. That is deliberate. Two assessors given the same building and the same information should return the same answer.

It is worth being clear about what SBEM is not. It is a compliance and certification tool, not a design tool, and it must never be used to size plant. The operating conditions in the calculation are standardised, so the output is a compliance score rather than a prediction of what the building will cost to run.

How is an SBEM assessment completed?

The software takes your building and builds a shadow copy of it, called the notional building. Same size, same shape, same orientation, but fitted out to a fixed government specification. The performance of that notional building becomes your target, and your real building has to match or beat it on two counts.

Those two counts are carbon emissions and primary energy. Your Building Emission Rate has to be no higher than the Target Emission Rate, and your Building Primary Energy Rate has to be no higher than the Target Primary Energy Rate. Both have to pass. Beating one comfortably does not buy you room on the other.

The main inputs the assessment looks at are:

• U-values for the walls, roof, floors, windows and doors
• Air permeability
• Internal lighting efficacy and controls
• The efficiency of the fixed building services, including HVAC and domestic hot water
• Any on-site renewable generation

Because the target is generated from your own geometry, design decisions move the target as well as the result. A heavily glazed elevation does not get matched glazing in the notional building. The notional applies a capped glazing allowance by building type, so the extra glass has to be paid for elsewhere in the specification.

When is an SBEM assessment required?

An SBEM assessment is required for new non-domestic buildings, for extensions above the size thresholds, for a material change of use or change in energy status, and whenever a non-domestic building is sold or let. In practice that covers most commercial work that reaches building control.

New non-domestic buildings. Offices, warehouses, retail units, shopping centres, schools, hotels, gyms and industrial units. The assessment is needed at design stage, before building control sign off.

Extensions. An extension to an existing non-domestic building is treated as a new building, and needs a full assessment, where its total useful floor area is both greater than 100m² and greater than 25% of the total useful floor area of the existing building. Both conditions have to be met. Smaller extensions still have to comply with Part L, but they are dealt with element by element rather than through a whole building calculation.

Change of use. Converting a building into a different use, for example a residential dwelling becoming a shop, brings the work within the energy efficiency requirements.

Change in energy status. This one catches people out. It means taking a building that was previously outside the energy efficiency requirements, typically an unheated space, and bringing it inside them by adding insulation and a heating system. A cold store or an agricultural barn converted into a heated workspace is the common example.

Sale or let. This triggers the EPC requirement, and the non-domestic EPC comes out of the same calculation.

What is the difference between SAP and SBEM?

SAP is used for dwellings, and SBEM is used for buildings other than dwellings. SAP assesses the dwelling as a whole rather than room by room, and its data requirements for fixed services are lighter. SBEM splits the building into zones by the activity that takes place in each space, so an office, a corridor and a toilet are modelled differently.

The practical consequence shows up on mixed use schemes. Flats above a commercial ground floor need both calculations, SAP for the dwellings and SBEM for the non-domestic parts, including any conditioned communal areas. Commission only one and the gap tends to surface at completion, which is the most expensive moment to find it.

There is one further distinction worth knowing. Rooms for residential purposes, such as hotel bedrooms and student rooms without their own self-contained facilities, are assessed through SBEM rather than SAP, even though people live in them.

What information is needed for an SBEM assessment?

The result depends almost entirely on the quality of the information supplied. Where information is missing, the software applies cautious defaults, and those defaults can fail a building that would otherwise have passed.

Drawings

• Floor plans
• Elevations
• Sections
• A site plan showing the orientation of the building

Fabric

• U-values or build-up specifications for the walls, roof and floors
• U-values and g-values for any glazed openings
• U-values for solid doors
• A target air permeability rate, which we provide and which is passed to the air pressure tester

Services

• The HVAC schedule with efficiencies
• The ventilation strategy
• Details of the proposed lighting
• The hot water system
• Any solar PV or other renewables

It is very normal that all of this information is not available at design stage. Where something is undecided, we work from an indication of what is likely to be installed, and issue a schedule of exactly what has been entered into the assessment, so you know what has to be delivered on site to keep the building compliant.

When is an air pressure test required?

Non-domestic buildings with a total floor area over 500m² must have an air pressure test. Below that threshold a test can be avoided, but the calculation then has to use a penalty air permeability figure of 15 m³/(h.m²) at 50Pa, which most buildings will not pass on.

That is why we recommend testing regardless of size in most cases. The design air permeability we issue is a compliance input rather than an aspiration, so the figure needs to be one the contractor can actually achieve. If the as built test misses it, the model has to absorb the difference, and that is when specifications start getting reopened.

What do you receive to submit to building control?

There are two stages, and you receive documents at each.

At design stage:

• An as designed BRUKL report
• A draft EPC
• A summary of the building specification entered into the assessment

At as built stage:

• An as built BRUKL report
• The EPC

The as built stage follows checks on what was actually installed at completion, including the measured air permeability result. Substitutions and value engineering between the two stages are normal. Telling your assessor when they happen, rather than at practical completion, is what keeps the second report as straightforward as the first.

What changes under Part L 2026?

Approved Document L Volume 2 (2026) was published on 24 March 2026 and comes into force on 24 March 2027 for non-higher-risk building work, and 24 September 2027 for higher-risk building work. Transitional provisions apply building by building rather than site by site, so on a phased scheme some buildings can fall either side of the change.

For non-domestic work the headline is continuity. SBEM remains the calculation method. Non-domestic buildings are not moving to the Home Energy Model, which is the replacement for SAP on the domestic side. The compliance metrics stay the same, with both a Target Emission Rate and a Target Primary Energy Rate. An Energy Use Intensity metric was pushed by parts of the industry and was not adopted.

What changes is the difficulty. The notional building specification is stronger, it assumes more solar PV than the Part L 2021 notional, and it points firmly towards low carbon heat. Schemes leaning on gas heating, modest fabric and no on-site generation will find the targets harder to reach.

One practical point. The approved software for England still runs the 2021 methodology, so no genuine Part L 2026 compliance figure can be produced yet. What you can do now is check where your scheme sits against the transitional dates, and stress test the specification against the direction of travel.

Frequently asked questions

Is an SBEM the same as a commercial EPC? No, but they come from the same calculation. The SBEM assessment produces the BRUKL report used for Part L compliance, and the same model produces the non-domestic EPC. One piece of work, two outputs.

Do I need an SBEM for a small extension? Only where the extension is both over 100m² of floor area and over 25% of the existing building's total floor area. Below that, the extension still has to meet Part L, but compliance is shown element by element rather than through a full assessment.

Can you do SAP and SBEM on the same project? Yes. Mixed use schemes normally need both, SAP for the dwellings and SBEM for the non-domestic parts. It is worth confirming early which calculation covers which part of the building.

What happens if my building fails the assessment? We tell you why, and what will fix it. Failures are usually traced to a small number of inputs, most often glazing area, fabric U-values, air permeability or the heating strategy. Catching it at design stage costs a specification change. Catching it at completion costs considerably more.

How long does an SBEM assessment take? Turnaround depends on the size of the building and how complete the information is. We issue a fixed price quotation within 15 minutes of receiving your drawings, and confirm the timescale with it.

Need an SBEM assessment? Send your drawings over and we will come back to you with a fixed price quotation within 15 minutes. Phone and email support is free before you instruct us. QUOTE