RdSAP 10.0.1: what it means for existing homes

The current version

The government identifies RdSAP 10.0.1 as the current methodology for assessing existing dwellings. RdSAP uses information collected during a non-invasive site survey together with standard assumptions where construction details cannot be directly established.

The version matters because methodology changes can affect inputs, assumptions, recommendations and the resulting rating. An older EPC and a new assessment should not be expected to match automatically, even when the dwelling appears unchanged.

Evidence still matters

Accessible documentary evidence can reduce reliance on default assumptions. This may include records for insulation, extensions, replacement glazing, heating systems or renewable technologies, provided that the evidence is suitable for the assessment convention being applied.

Homeowners arranging an EPC should gather relevant certificates, invoices and building-control information before the visit. The assessor must still follow the approved methodology and accreditation guidance rather than accept unsupported descriptions.

A practical reading of the result

An EPC is a standardised assessment, not an energy bill prediction or an invasive building survey. Its strength is consistent comparison. When a result will support a sale, letting, funding application or improvement plan, explain the purpose before the survey so that the correct evidence can be considered.