SBEM Calculations for Part L Compliance

Simplified Building Energy Model (SBEM) calculations are a government-approved method used to demonstrate compliance with Part L of the Building Regulations, which governs the energy performance of non-domestic buildings in the UK. Part L aims to reduce carbon emissions by ensuring buildings are designed and constructed to be energy efficient.

SBEM assessments evaluate a building's predicted energy usage based on factors such as insulation, heating, lighting, ventilation, and renewable technologies. The software compares the building’s performance to a Target Emission Rate (TER), which represents the maximum allowable CO₂ emissions for a building of that type. The result is a Building Emission Rate (BER); to comply, the BER must not exceed the TER.

SBEM calculations are required at two key stages: Design Stage (before construction) and As-Built Stage (after construction). At the Design Stage, the results inform decisions on materials and systems to ensure compliance, while the As-Built assessment confirms whether the completed building meets regulations.

Compliance with Part L also involves meeting minimum fabric performance standards and demonstrating appropriate use of energy-saving technologies. A successful SBEM assessment leads to the issue of a Building Regulations UK Part L (BRUKL) report and an Energy Performance Certificate (EPC), both of which are essential for building sign-off and occupancy.

TM52 Overheating Analysis of Non-Domestic Buildings

TM52 is a methodology developed by CIBSE (Chartered Institution of Building Services Engineers) to assess the risk of overheating in non-domestic buildings, particularly in naturally ventilated spaces. As the UK climate warms and energy efficiency standards improve building airtightness, the risk of overheating has become a growing concern, especially during the summer months.

TM52 defines three criteria based on internal temperature and occupancy to evaluate whether a space is likely to cause thermal discomfort:

1. Hours of Exceedance – the number of hours the internal temperature exceeds a comfort threshold.

2. Daily Weighted Exceedance – the severity of overheating on a daily basis.

3. Upper Limit Temperature – the maximum acceptable indoor temperature.

If a space fails two or more of these criteria, it is considered at risk of overheating.

The assessment uses dynamic thermal simulation modelling, typically with software like IES, TAS or DesignBuilder and is based on real occupancy patterns, internal gains, and local climate data. TM52 is especially relevant for spaces like schools, offices, and healthcare settings.

By identifying overheating risks early in the design process, TM52 helps inform passive and active design strategies (e.g., shading, natural ventilation, thermal mass) to ensure occupant comfort and long-term building resilience.

TM54 Operational Energy Analysis of Non-Domestic Buildings

TM54 is a guidance document published by CIBSE that addresses the gap between predicted and actual energy use in non-domestic buildings. Traditional design-stage energy models (like SBEM or EPC assessments) often underestimate real-world energy consumption because they are based on standard assumptions and compliance targets rather than actual operation. TM54 helps designers and engineers create more accurate energy estimates by modelling operational energy performance.

The methodology involves creating dynamic simulations that reflect realistic assumptions about building occupancy, equipment loads, operational schedules, and system performance. TM54 encourages using sensitivity analysis to explore how variations in these assumptions impact overall energy use.

TM54 divides energy use into categories such as regulated loads (heating, cooling, lighting) and unregulated loads (equipment, small power, lifts), allowing a more comprehensive picture of total operational energy. It also accounts for controls, maintenance, and user behaviour, which significantly influence real performance.

By applying TM54 during design, project teams can identify potential inefficiencies early, optimise system choices, and set realistic energy performance targets. This approach supports better-informed decisions that align with net-zero carbon goals and energy management strategies, helping to bridge the performance gap and deliver buildings that perform as intended in actual use.

Energy Statements for Planning

An Energy Statement is a key document submitted as part of a planning application to demonstrate how a proposed development will meet local and national energy and carbon reduction targets. It outlines the strategy for reducing energy consumption and carbon emissions through a combination of energy efficiency measures, low-carbon technologies, and renewable energy systems.

Typically required for major developments (and increasingly for smaller schemes), Energy Statements align with local planning policies, the London Plan (for London-based projects), and national objectives such as the UK’s net zero targets. The document follows the “Be Lean, Be Clean, Be Green” energy hierarchy:

1. Be Lean – Improve energy efficiency through building fabric, lighting, and systems.

2. Be Clean – Use efficient heating systems or connect to decentralised energy networks.

3. Be Green – Incorporate renewable energy sources like solar PV, heat pumps, or wind.

The Energy Statement includes estimated carbon savings at each stage of the hierarchy, supported by calculations and modelling (often using SAP or SBEM). It also considers future climate resilience, energy infrastructure, and potential overheating risks.

Ultimately, Energy Statements help planning authorities assess whether developments contribute to sustainable growth and comply with relevant energy and environmental policies before granting planning permission.