SBEM – Parts L1B, L2A and L2B of the Building Regulations

SBEM, or Simplified Building Energy Model, provides an analysis of the predicted energy performance of a building.

The SBEM calculates the monthly carbon dioxide emitted based on the calculated energy demand of a building given its construction, geometry, use type, lighting equipment and plant (HVAC).  SBEM ratings are scored from a scale of 1 to 100, with 1 being the worst and 100 being a zero usage of energy.

In order to comply with Building Regulations Part L1B (domestic refurbishment, extensions, renovations) and L2B (non-domestic refurbishment, extensions, renovations) it is often necessary to have SBEM calculations carried out (this requirement should be checked with your local Building Control Office).  The SBEM calculations produce an SBEM report certificate which shows the SBEM rating for the building in question.  If the SBEM report certificate shows a pass then the project passes Part L of the Building Regulations.  SBEM calculations and the requirements of the SBEM report vary between new build, extension and conversion projects.

New build SBEM calculations work out a Target Emission Rating (TER) followed by a Building Emission Rate (BER).  The BER must be equal to or less than the TER in order for the SBEM rating to show a pass on the SBEM report certificate.

When non-domestic buildings are extended the above SBEM calculation rules apply but only to the new build portion of the building.  The SBEM requirements do not apply to the existing section of the building.

SBEM calculations for conversion projects are different however.  The SBEM report needs to show that the thermal elements such as walls, floors and glazing have been updated to minimum standards.

The Process

The first part of the SBEM calculations involves the assessor working out a Target Emissions Rate (TER) for the building using drawings and building specification information. The next step is the calculation of the Building Emission Rate (BER).  If this is equal to or less than the TER then the SBEM report shows a pass and the SBEM calculations are complete.  The SBEM report will then be sent to the client, either electronically and/or as a paper copy, to be passed on to Building Control.
If the BER is not equal to or less that the TER then the SBEM assessor will liaise with the client and suggest changes that will aim to improve the BER to a level that the SBEM calculations show a pass.

All new buildings, including extensions, which are greater than 500m² will require an Air Leakage Test upon completion.

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