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The government is about to turn up the heat on landlords as Energy Performance Certificates undergo a major technical overhaul.
As of June 15, the methodology for EPC rating changes, which is expected to result in more accurate assessments.
The new tool is the Reduced Data Standard Assessment Procedure 10 (RdSAP 10).
Housing professionals welcome the EPC upgrade, but fear assessments will cost landlords more.
The Reduced Data Standard Assessment Procedure 10 (RdSAP 10) is a complex name for a simplified methodology used to assess Energy Performance Certificates (EPCs) in homes. The formula makes assumptions about a building's construction and usage to generate a rating of a property's energy efficiency.
RdSAP will be introduced from June 15, 2025, and incorporates new data inputs, revised assumptions, and structural changes designed to align EPCs closer to the property's real-life energy performance.
Improved data collection
Under RdSAP, energy assessors will record more specific information about a home, 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.
Hard-to-spot home improvements, like added insulation or new windows, will only be reflected in an EPC if the landlord can provide evidence of the work.
This means EPCs will now depend much more heavily on the documentation that homeowners, landlords, and agents can provide.
Detailed heating system reports
RdSAP will rate a heating system's efficiency based on the manufacturer's documentation rather than default assumptions. If no documentation is provided, the system's efficiency may be rated lower, which could potentially impact the EPC score.
Better floor area and insulation modelling
The update includes improved methods for calculating floor area and insulation levels, giving a more precise picture of a home's heat retention and energy use.
New energy efficiency treatments for flats and terraced homes
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.
Landlords must show evidence of energy improvements. Keeping accurate records and receipts for an EPC will be critical, especially for insulation, heating upgrades, and double glazing. EPC ratings might drop if no evidence is provided, even if costly improvements have been made, so having a clear paper trail can protect property owners from unnecessary retrofit costs.
Cash-in-hand improvements will no longer benefit landlords as they must provide invoices and other documentation to gain the maximum rating for energy efficiencies they have carried out.
EPCs are likely to become more expensive as assessors will need to spend more time on collecting data and producing reports, says letting agent trade body PropertyMark.
EPCs carried out before June 15 will follow the current assessment methodology.
Landlords do not have to obtain an RdSAP 10 version EPC until their current version runs out.