What are SAP calculations and when are they required?

SAP calculations assess the predicted energy performance of a dwelling. They are commonly required for new-build homes, conversions and certain extensions to demonstrate Part L compliance.

What is needed for an on-construction EPC?

The final SAP or SBEM model must reflect the completed building, supported by confirmed construction specifications, test results and commissioning evidence.

What does an Energy Statement include?

An Energy Statement normally describes planning policy, the proposed energy strategy, demand-reduction measures, low-carbon systems, renewable energy and the resulting carbon improvement.

PRACTICAL GUIDE

SAP calculations or an EPC?
Know what your project needs.

The terms are closely connected, but they are not interchangeable. The correct route depends on the building and project stage.

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The short answer: SAP is the assessment; the EPC is an output

A SAP calculation models the predicted energy performance of a dwelling and is used to demonstrate compliance for a new home or certain conversion and extension projects. An EPC is the certificate that records a building's energy rating. For a newly completed dwelling, the final EPC is generated from the as-built SAP assessment.

New build or residential conversion

A new dwelling normally needs a design-stage SAP calculation before construction details are fixed. At completion, the model is updated using the final specification, air-test result, commissioning information and evidence of installed products. The as-built SAP reports and on-construction EPC can then be produced.

Extension to an existing home

An extension does not normally receive its own EPC. Compliance may be demonstrated through elemental standards or, where glazing or design choices go beyond the usual limits, a SAP-based whole-dwelling calculation. Building Control should confirm the route required for the specific project.

Selling or letting an existing home

An existing dwelling usually needs a domestic EPC survey rather than a full design-stage SAP assessment. The assessor records the property, construction, heating, glazing and evidence of insulation using the applicable existing-dwelling methodology. If the property is newly created or not yet completed, the on-construction route may apply instead.

COMMON QUESTIONS

Clear answers.
No guesswork.

01Is a SAP calculation the same as an EPC?+

No. SAP is the detailed energy calculation used for dwelling compliance. The EPC is the certificate showing the resulting energy rating; for a new dwelling it is generated from the final SAP model.

02When should I appoint a SAP assessor?+

Ideally during design, before insulation, glazing, heating, ventilation and renewable specifications are fixed. Early assessment leaves more options available if the first design does not comply.

03Can an existing EPC be used for Building Control?+

An existing-home EPC does not normally replace the design and compliance calculations required for a new dwelling, conversion or extension. Confirm the requested evidence with Building Control.

04What should I send for a quotation?+

Send the project address, proposed drawings, project type and stage, plus any Building Control or planning request. We will confirm whether SAP, EPC, SBEM or another assessment route applies.

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