Why is my EPC (Energy Performance Certificate) rating different to my predicted result?
When you receive your Part L design reports from your SAP assessor, you should receive a Predicted Energy Assessment. This tells you what the expected Energy Performance Certificate rating of your new home will be.
The EPC is a report which gives your home an A-G rating, where A is the most efficient and G is the least efficient. Most new homes score a B or C rating.
Sometimes this rating will change by the time your building is constructed. There are a number of reasons for this to happen.
The most common reason for a different figure is if you have made alterations to the building fabric or heating systems since your PEA was produced. Any change which ultimately affects the amount of fuel needed to heat and power your home will have a knock on effect on the EPC.
Another key reason is a change in methodology. Every few years the SAP calculator is updated to reflect latest trends and fuel prices. If this update occurs between the publication of your PEA and your EPC, you may notice a change.
If you score a better-than-expected air test on your home, this information will be fed back into the SAP and you could receive a better EPC score because of it. Similarly though, achieving a worse than expected air test result could lead to a worse rating, so make sure you know from your SAP assessor what is expected from your air leakage test.