SAP Calculations
For Conversions

Conversion Projects & Change Of Use (Part L1b)

Under Part L1b of the building regulations you are required to provide a SAP calculations when converting an existing non-domestic building into a residential dwelling or property. This is commonly known as "change of use". Typical scenarios include barn conversions, converting offices, shops and any other commercial building into a residential property.

The purpose of the SAP calculation is to demonstrate that the existing buildings insulation will provide adequate thermal properties to the occupants where previously the building use didn't require. Typically in barn conversions this may require the existing walls, floors and roofs to be insulated. For existing shops and offices this may require little to no changes in the insulation dependant on the age and construction of the building.


The requirements for conversion project aren't a strict as new build standards and allow for existing elements of the building to be incorporated into the design.

Upon completion of a dwelling the SAP calculation is used to prepare the Energy Performance Certificate (EPC).

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