Home Energy Assessments – RdSAP 10 Updates!

Find out how the methodology changes will affect EPC survey results from June 2025.

What’s RdSAP 10?

RdSAP 10 is a methodology used for measuring a property’s home energy efficiency. Across the UK, RdSAP 10 outlines the data and baseline assumptions which domestic energy assessors use to give you your Energy Performance Certificate Score.

The assessment framework is under review constantly in order to improve the accuracy of energy measurements and give homeowners the best reports possible.

Change is Coming – What You Need to Know

Assessors will collect more data about your home – including window glazing, added insulation and smart heating controls.
Heating Systems will be assessed based on an updated hierarchy of actual evidence. Fewer assumptions would be made so your score has the potential to be more accurate!
Walls, roofs and floors all have new options when measuring, including new types and insulation thicknesses.
Flats and terraced homes now have updated heat loss calculations to avoid incorrect assumptions.
Introduction of mechanical ventilation and draughtproofing options. The inclusion of air tightness test results allowing building performance to be measured.

What does that mean for me?

For homeowners, these updates will change the way EPCs are scored – favouring those properties which have made energy efficiency improvements. Your EPC report can give you a good grounding for making energy efficiency changes to your home, however these recommendations are not always what we consider best practice or suitable for your home.

For landlords, EPCs are necessary for MEES compliancy and provide a pathway for them to improve their property. The assessment duration will be affected by the enhanced report criteria, with assessors spending more time in your home to ensure correct data gathering.

At Retrofit West, our Home Energy Efficiency Plan (HEEP) includes a new EPC assessment, alongside a report including retrofit measures, cost estimates and the likely impact on energy bills, carbon emissions, and improvement to your Energy Performance Certificate (EPC) rating.

For Domestic Energy Assessors, more detailed and accurate data options when assessing properties can aid delivery of better EPC reports. The reports can better reflect the home’s true energy consumption and lend better options for improvements. The assessment duration will be affected by the added data collection methodology, so stay on top of updates to ensure preparation for the transition.