SBEM Energy Calculations: what are they, and why do they matter?

Buildings – whether dwellings or commercial premises – account for a significant proportion of the UK’s carbon emissions. It should come as no surprise to learn that extensive effort is being made to bring those emissions down in order to reduce the UK’s overall carbon footprint as the country works to meet the 2050 net zero carbon deadline.

In its 2020 ‘Ten Point Plan for a Green Industrial Revolution’, the UK Government stated, “We will put our homes, workplaces, schools and hospitals at the heart of our green economic recovery, supporting 50,000 jobs and building new supply chains and factories in the UK.

“Making our buildings more energy efficient and moving away from fossil fuel boilers will help make people’s homes warm and comfortable, whilst keeping bills low. We will go with the grain of behaviour, and set a clear path that sees the gradual move away from fossil fuel boilers over the next fifteen years as individuals replace their appliances and are offered a lower carbon, more efficient alternative.”

Simplified Building Energy Model energy calculations (SBEM) are used to assess the energy performance of commercial buildings in the UK, much like how the government’s Standard Assessment Procedure (SAP) is used to assess residential dwellings. As with SAP calculations, SBEM has been developed to verify compliance with Part L of the Building Regulations relating to energy standards.

Government-approved and based on a model that calculates the energy use of a building over a typical year, SBEM energy calculations are an important tool for building designers and owners. They help stakeholders to understand the building’s energy efficiency and potentially find ways to improve it.

How does it work?

The SBEM model takes into account a range of factors in order to assess a commercial building’s energy performance. Among these factors are:

  • The building’s size
  • Materials
  • Location
  • Orientation and
  • The efficiency of its HVAC systems (Heating, Ventilation, and Air Conditioning).

Other energy-consuming systems, such as the building’s electrical appliances and lighting, must also be taken into account.

Obviously, the result cannot be reliable if it’s not based on accurate information. To correctly carry out SBEM energy calculations, the designer or owner of the commercial building must provide detailed information about the building – including all the factors mentioned above, and many more.

All information is then entered in a software tool; while various tools may be used, including iSBEM, IES and DesignBuilder, they all use the SBEM methodology. The tool calculates the energy use of a building using a simplified set of assumptions and default values. These are based on typical building construction practices and energy use patterns. The calculations must be carried out by a qualified energy assessor, trained to use the relevant software tool.

The results of SBEM energy calculations can be used to identify ways to improve the energy performance of a building. This assists the building designer or owner in making changes to the building’s design in order to become more energy efficient.

Despite their role in informing design changes, it should be noted that SBEM calculations are not a design tool. SBEM’s main function is to provide a Building Regulation UK Part L Report (BRUKL), as well as informing the Energy Performance Certificate (EPC) of the building.

Both are vital – let’s see why.

Why does it matter?

SBEM energy calculations are a key part of the UK Building Regulations. Part L of the Building Regulations sets out requirements for the conservation of fuel and power in buildings; it applies to all new buildings, as well as to some refurbishing work on existing buildings – notably to any extension exceeding 100m2 and greater than 25% of the total floor area of the existing building.

In order to ensure compliance with the required energy standards, SBEM calculations are required. The output of the SBEM calculations is a Building Emission Rate (BER) and a Target Emission Rate (TER). The former represents the predicted carbon emissions from the building, while the latter represents the maximum emissions allowed under Part L. The building must achieve a BER that is equal to or lower than the TER to comply with Part L of the UK Building Regulations.

If the assessment is not passed, building works cannot commence. This is why it’s advisable to submit the information needed for SBEM energy calculations early in the design phase. The project can then be easily amended where needed with minimal disruption.

SBEM calculations play another essential role, as they inform the building’s predicted Energy Performance Certificate (EPC). The EPC provides information about the energy efficiency of a building, rating it on a scale from A (most efficient) to G (least efficient). Under UK law, EPCs are often required for all buildings; no commercial building or dwelling can be let or sold without one.

An EPC is valid for 10 years; once the 10 years are up, there is no requirement to get a new EPC unless the property is to be sold or let. Under current regulations, a property must achieve an EPC rating of E or above in order to be legally let.

However, this will change by April 2025, with more stringent regulations set to come into force in England and Wales: all rental properties will need an EPC rating of C or above in order to be let. This will first apply to new tenancies but will be extended to all tenancies by 2028. The penalty for not having a valid EPC where necessary will also be raised in 2025, from the current £5,000 fine up to £30,000.

With roughly 61% of EPC certificates lodged in England from April to June 2022 for non-domestic properties having a rating equal to or above C, it is clear that efforts are being made – but more can still be done to improve energy efficiencies. SBEM calculations remain key to accurately predicting a building’s EPC rating before construction begins and intervene to improve it, thus benefiting from the energy savings and reduced carbon emissions that come with an energy-efficient building.

Tags: SBEM, energy saving, net zero, commercial property

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