What Is SBEM?

SBEM (Simplified Building Energy Model) is the government's calculation tool for assessing the energy performance of non-domestic buildings in England and Wales. It implements the National Calculation Methodology (NCM) and is used to produce BRUKL compliance reports demonstrating that a building meets Part L requirements (AD L2 2026).

What SBEM calculates

SBEM calculates two key performance metrics for a non-domestic building:

• Building Emission Rate (BER) – the predicted CO₂ emissions per square metre per year (kgCO₂/m²/year)
• Building Primary Energy Rate (BPER) – the predicted primary energy consumption per square metre per year (kWh/m²/year)

These are compared against the Target Emission Rate (TER) and Target Primary Energy Rate (TPER), both derived from the notional building. For compliance, BER ≤ TER and BPER ≤ TPER must both be satisfied.

Relationship to the National Calculation Methodology

The National Calculation Methodology (NCM) is the approved framework for calculating non-domestic building energy performance. SBEM is one implementation of the NCM – the other being approved Dynamic Simulation Modelling (DSM) software such as IES Virtual Environment or TAS.

The NCM defines standard operating conditions (occupancy hours, internal gains, HVAC schedules) for different building types, so that buildings can be compared on a like-for-like basis regardless of how they will actually be used.

When to use SBEM vs Dynamic Simulation

SBEM is suitable for most straightforward non-domestic buildings. It uses a monthly calculation method and handles common HVAC systems well. Dynamic Simulation Modelling (DSM) is required or recommended when:

• The building has complex HVAC systems (e.g., displacement ventilation, chilled beams, mixed-mode ventilation)
• The design includes advanced daylighting strategies that SBEM cannot model
• The client wants to demonstrate performance beyond the minimum compliance requirement
• The building has an unusual geometry or multiple interconnected zones

iSBEM software

iSBEM is the government's free interface for the SBEM calculation engine. It provides a graphical user interface for entering building geometry, construction details, HVAC systems, lighting, and other parameters. The output is a BRUKL report documenting compliance.

Commercial alternatives to iSBEM include third-party software that implements the NCM through the SBEM engine, sometimes offering additional modelling features or integration with architectural design tools.

How the FBS changes SBEM compliance

Under the Future Buildings Standard, the notional building specification has been tightened significantly. This means the TER and TPER are lower (harder to meet) than under Part L 2021. Key changes include:

• Tighter fabric U-values in the notional building
• Low-carbon heating assumed in the notional building
• Solar PV included in the notional building (40% of foundation area for both side-lit and top-lit zones; none if 100% heat pump heating)
• Higher lighting efficacy (105 lm/W)

These changes mean that buildings which would have complied under Part L 2021 may no longer meet the FBS targets without design improvements. See BRUKL under FBS for practical guidance on how the compliance bar has moved.

Who can use SBEM?

SBEM assessments must be carried out by a qualified Non-Domestic Energy Assessor (NDEA) registered with an accreditation scheme. Qualification levels include:

• Level 3 – simple buildings with standard HVAC
• Level 4 – complex buildings using SBEM
• Level 5 – complex buildings using Dynamic Simulation Modelling