An on construction domestic Energy Performance Certificate (EPC) is required for all domestic new builds. Assessors must be specifically trained and accredited to provide on-construction domestic EPCs and a standard domestic EPC is not valid for the first assessment of a property built to 2006 regulations.
An initial SAP calculation (Predicted Energy Assessment) is required at the design stage as part of the building control submission. The detailed design must produce a SAP pass and it is increasingly common for authorities to demand an improvement to the standard of Code Level 3.
The final SAP calculation is undertaken after completion and must include the result of a relevant air pressure test. Any changes to the design are included in this calculation and assuming a pass, then an EPC is generated.
If any changes are made during construction then it is always preferable to update the SAP calculation immediately to ensure that an appropriate pass level is maintained. Specification changes during construction can easily lead to a SAP fail and necessitate costly rework.