EPC calculations - criteria

Does anybody know the criteria for how EPCs are measured.
I was wondering if the criteria had changed as new technologies for energy efficiency have become available.
There have been a couple of things lately that have made me wonder - I know at least one other member wondering about EPC calculations that don’t add up !! @Ann_Kolodziejski
Is there a calculator that the public can access or do we know of any changes.

Thanks in advance.

EPC’s are really guesswork but officially they follow the rdSAP formula, which I believe is in the public domain.

SAP is used by architects to pass regulations and give themselves a pat on the back. However SAP doesn’t include any cross reference to the actual building designed and built.

The “rd” refers to reduced data” and these are partially specified in the regulations and partially guesswork by the assessor. All guesses should be declared, such as “Solid floor. Uninsulated (assumed)”. The biggest guess is that the building met Building Regs at the time of construction.

I know of a couple of changes to SAP and hence rdSAP over the years. They are linked to updates to building regulations.

A suspicious number of rented properties meet the minimum EPC rating by one point. Either landlords are very good at hitting the mark or assessments are not entirely independent.