A comprehensive guide for new builds, conversions, and extensions.

For architects, MEP consultancies, commercial developers, and planning consultants, SBEM (Simplified Building Energy Model) calculations play a critical role in ensuring energy efficiency and compliance for non-domestic buildings. This guide provides an in-depth look at SBEM calculations, their purpose, the process, and how to avoid common pitfalls.

What Are SBEM Calculations?

SBEM calculations evaluate the energy performance of non-domestic buildings in the UK. These assessments – which are developed by the government – use building geometry, construction materials, and systems specifications (for example, HVAC and lighting) to calculate energy use and carbon dioxide emissions.

The results help generate:

• A BRUKL (Building Regulations UK Part L) report to demonstrate compliance with Approved Document Part L Volume 2 of the Building Regulations.
• An Energy Performance Certificate (EPC) required for legal occupancy, sale, or rental of commercial properties.

When Are SBEM Calculations Required?

•  New Non-Domestic Buildings

Required to demonstrate compliance with Part L Regulations 26 and 26C, ensuring the building meets the Target Primary Energy Rate and Target Emission Rate.

Assessed at both the design stage (pre-construction) and as-built stage (post-construction).

•  Extensions

Mandatory for extensions over 100m² or exceeding 25% of the existing floor area, ensuring energy and emissions targets are met.

•  Material Changes of Use

When a building's purpose changes and it becomes subject to energy efficiency requirements, SBEM calculations verify compliance.

•  Shell and Core Developments

Required for the base build during design and when fixed services are added at the first fit-out stage.

•  Consequential Improvements

Triggered for large buildings (>1000m²) undergoing significant upgrades, such as increased HVAC capacity.

•  Special Cases

Temporary buildings (used for over two years), modular buildings, and swimming pools require modelling for compliance.

Why Are SBEM Calculations Required?

Regulatory Compliance: Ensure adherence to Approved Document Part L Volume 2 energy efficiency standards.

Sustainability Goals: Support carbon reduction and energy conservation efforts.

Compliance Documents: Produce BRUKL reports for Building Control approval and EPCs for sale or rental.

Energy Optimisation: Provide actionable insights to reduce operational costs and improve building efficiency.

The SBEM Assessment Process

Design Stage Assessment

• Uses architectural plans, material specifications, and fixed building services (e.g., heating, cooling, ventilation, and lighting) to model energy use.
• Ensures compliance at the planning and early construction stages, minimising redesign risks.

As-Built Assessment

• Conducted after construction to reflect any deviations from the design.
• Ensures compliance with BRUKL and Part L standards using updated, real-world specifications.

Air Pressure Testing

• Mandatory for >500m² floor area commercial buildings to measure airtightness.
• Provides data to verify energy loss through the building envelope and ensure compliance with SBEM predictions.
• Exemptions: Smaller buildings under 500 m² do not require air testing if a justifiable level of airtightness is assumed.

Common Pitfalls and How to Avoid Them

• Late Engagement: Delaying SBEM assessments can lead to costly redesigns. You should engage assessors early to integrate energy efficiency into the design.
• Inadequate Specification: Poorly detailed HVAC systems, lighting, and insulation can lead to non-compliance. You need to work with experienced consultants to ensure specifications align with standards.
• Insufficient Documentation: Missing details, such as lighting layouts and HVAC schematics, can delay assessments. This is why it’s important to ensure all required data is prepared early.
• Overlooking Airtightness: Ignoring airtightness standards can result in compliance failure. Conduct proper air pressure testing to avoid energy losses.

Cost and Duration of SBEM Calculations

Cost: SBEM calculations typically range from £250 to £5,000 (a large disparity, we know), depending on the building's size and complexity. Fees may also increase for large-scale developments or intricate energy modelling requirements.

Duration: Completion times vary but generally take 5 to 10 working days, provided all necessary information is available. Delays in documentation submission can extend timelines.

*Note: Prices can increase and decrease dependant on a building’s complexity and also the quantity, the figures above are based on basic buildings; it's advisable to obtain a tailored quote.*

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SBEM calculations are not just a regulatory requirement—they are a fundamental part of designing and constructing energy-efficient, compliant non-domestic buildings. By evaluating a building’s energy performance against the standards set out in Approved Document Part L Volume 2, SBEM calculations ensure that properties meet modern energy efficiency and carbon reduction targets.

For architects, these assessments provide a framework for integrating sustainable design principles without compromising functionality. For MEP consultants, they guide the specification of efficient building services such as heating, ventilation, and lighting. For commercial developers and planning consultants, SBEM calculations validate that projects align with regulations and market expectations, reducing delays and risks at critical stages of development.

Moreover, SBEM assessments contribute to long-term cost savings. By identifying opportunities to reduce energy consumption and operational expenses, they enhance a building's market value and environmental performance. In today’s landscape, where sustainability is a priority, SBEM calculations are more than compliance—they’re a cornerstone of responsible building practices. Engaging an experienced SBEM assessor early in the project ensures a smoother path to compliance, avoiding costly redesigns and delays. Whether for new builds, extensions, or complex developments, SBEM calculations are a key step in achieving energy-efficient, future-proof buildings.