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SAP Calculations for extensions

UKBC are registered SAP Assessors with Stroma.

L1B SAP calculations are required for certain extensions to make sure your extension complies with Part L (England & Wales), Section 6 (Scotland) or Part F1 (Northern Ireland) of The Building Regulations. SAP calculations are concerned with energy efficiency and are needed to produce an updated Energy Performance Certificate (EPC) for the property. This is part of the government’s plan to reduce carbon emissions and tackle fuel poverty. It is important to note that it is against the law to rent or sell a dwelling without an EPC.

SAP Calculations for Extensions with UKBC

We recommend you commission your calculations at design stage. Therefore, should your building be failing to meet requirements, our team can advise you on how to improve. This is far easier and cheaper at design stage, when the scope of possible changes is more flexible. UKBC L1B SAP calculations for extensions come in two stages: a ‘notional report’ and a ‘proposed report’.

We compare these reports in order to produce an up-to-date EPC for the entire property.

This Process Includes:


  • Assessing the existing and proposed area of the external building fabric and openings.
  • Evaluating the building’s current construction materials and the extension’s proposed materials.
  • Measuring the energy consumption of the current and updated heating systems, lighting, ventilation systems and renewable technologies.
  • Next, we create a notional report with benchmarked data for the existing and proposed elements of the building, and a report with the proposed data for the existing building plus the extension.
  • Finally, we’ll analyse and compare the reports in SAP calculations software to make sure the data in the proposed report is lower than benchmarked standards.

Find Out More

UKBC will guide you through the entire process of getting SAP calculations for your new build, including consultation on how to make sure your building complies with Part L building regulations.

For more information about our SAP Calculation services, explore the sections below or contact us for a FREE Quick Quote via:

Telephone: 01455 634 855
Contact Form: HERE