Propertymark welcomes improvements that make EPCs more robust and meaningful. However, we continue to push for clear guidance and support for landlords and agents to navigate upcoming changes, realistic implementation timelines that allow the sector to prepare, and funding to help with the cost of improvements, particularly for small landlords
These themes are consistent with our wider work calling for reform of the EPC system, fairer access to retrofit funding, and better communication from governments to landlords and property professionals.
What is RdSAP?
The Reduced Data Standard Assessment Procedure (RdSAP) is the simplified methodology used for producing EPCs in existing dwellings. It uses assumptions about how buildings are constructed and occupied to generate a rating of a property's energy efficiency.
The version set to be introduced in June 2025, RdSAP 10, incorporates new data inputs, revised assumptions, and structural changes designed to bring EPCs closer to reality.
Key changes in energy assessments
Expanded data collection
Energy assessors will now collect and record more specific information about a property, including types of glazing and their condition, heating system efficiency based on evidence such as model numbers or manufacturer data, and the presence of smart heating controls. Home improvements, such as added insulation or new windows, will only be reflected if evidence is available.
This means EPCs will now depend much more heavily on the documentation that homeowners, landlords, and agents can provide.
More accurate assessment of heating systems
Previously, if a heating system’s details couldn’t be verified, default assumptions were used, often underestimating its efficiency. RdSAP 10 introduces a hierarchy that prioritises actual evidence over assumptions. If no documentation can be provided, the system’s efficiency may be rated lower, potentially impacting the EPC score.
Improved floor area and insulation modelling
The update includes refined methods for calculating floor area and insulation levels, providing a more precise understanding of a home’s heat retention and energy use.
Better treatment of flats and mid-terrace properties
RdSAP 10 adjusts how heat loss is calculated for flats and terraced homes, which were previously disadvantaged by default assumptions. This could lead to improved EPC ratings for these types of properties.
What does this mean for agents, landlords, and tenants?
Landlords will need to be more proactive in maintaining and providing evidence of energy improvements. EPCs are already a regulatory requirement for letting properties, and minimum standards (currently EPC E in England and Wales) mean that an inaccurate or lower-than-expected rating could block a tenancy.
Going forward, accurate records and receipts will be critical—especially for insulation, heating upgrades and double glazing. EPC ratings might initially drop if no evidence is provided, even if improvements have been made, so having a clear paper trail can protect property owners from unnecessary retrofit costs.
We strongly advise agents to encourage their landlords to begin gathering relevant documentation now, ahead of the transition.
The changes mean residents can have greater confidence in the accuracy of EPCs. Tenants may use this information to identify more energy-efficient homes, potentially lowering their energy bills. Homeowners looking to sell may find that a more accurate EPC helps them highlight energy efficiency improvements they've made—provided they can evidence them.
