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Does your non domestic extension need an SBEM

Does your non domestic extension need an SBEM? Check ouyt this simple checklist below to see.

Part L2B checklist to see if an SBEM is required

Refer to the list below from Section 4.2 of Approved Document Part L2B of the Building Regulations:

  • Is your extension over 100m2 AND;
  • Is the area of the extension more than 25% of the total useful floor area of the existing building?

If the answer is yes to both, then in theory, you need an SBEM to demonstrate compliance with Approved Document Part L2A of the Building Regulations. The assessment will only apply to the extension, but may take account of heating and hot water systems within the existing building.

Other triggers that may require an SBEM for a non-domestic extension:

  • If the area of glazing to the extension is in excess of those from Table 2 of Approved Document Part L2B of the Building Regulations indicated below:

opening areas in an extension


The SBEM will need to demonstrate the extension is as energy efficient with the same or lower carbon emissions that the equivalent extension with a compliant area of glazing.

Our advise would always be to check with your Building Control officer as some schemes that are borderline may be fine moving forward on the elemental method (i.e. maximum U values etc…)

Need help?

Low Carbon Box have a 100% success rate in gaining approval for over glazed extensions. Why not check out our services page and get in touch..

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