RdSAP changes to property performance assessment from June 2025

RdSAP changes to property performance assessment from June 2025

From mid-June 2025, the way we assess the energy performance of existing homes in the UK is changing. This is a significant update to the government-approved RdSAP methodology (short for Reduced data Standard Assessment Procedure), and it could reshape how properties are valued, marketed, sold, and upgraded across the country.

If you’re a developer, estate agent, landlord or retrofitter, these changes aren’t just technical tweaks in a spreadsheet. They’re meaningful shifts that affect everything from EPC ratings to funding eligibility to resale value.

What is the difference between SAP and RdSAP?

SAP and RdSAP are related but serve different purposes.

SAP is the full Standard Assessment Procedure used for new builds. It’s comprehensive, involving a complete set of data about a property’s construction and systems. Perfect for when you’re starting from scratch.

RdSAP, on the other hand, is designed for existing homes, where not every detail is available or, indeed, practical to collect. It uses a mix of actual data gathered during surveys and default values based on age, construction type and assumptions. It’s been the basis for Energy Performance Certificates (EPCs) in the UK since 2007.

Why does the distinction matter? Because if you’re evaluating a housing portfolio, listing homes for sale, or planning retrofit work, the assessment method directly affects the EPC outcome. And EPCs carry a lot of weight.

What are the upcoming changes and enhancements?

The updated RdSAP 10 goes live on 15 June 2025. It’s the most comprehensive update in years, designed to make EPCs more accurate and relevant to a home’s real-world performance.

A few of the biggest changes:

• Every window now has to be measured and its orientation recorded, instead of relying on assumed values.
• Room-in-roof types now have more detailed categories and require more measurements (like gable walls) for accuracy.
• New technology support includes PV diverters, battery storage systems, and heat pumps.
• Ventilation inputs have expanded, recognising systems like mechanical ventilation with heat recovery (MVHR).
• Property age bands have been refined, with a new band for homes built from 2023 onwards.
• Carbon emissions factors have been updated, particularly for electricity, which now reflects a lower emissions rate due to grid decarbonisation.

All of this adds up to a more detailed, up to date assessment that’s better aligned with the UK’s Net Zero ambitions.

How does RdSAP impact domestic dwellings?

RdSAP is what underpins the EPC status you see on almost every home listing these days. The little coloured bar chart might seem quite simple, but to deliver it requires a complex set of analysis, data gathering and calculations.

An EPC isn’t just about regulatory compliance (though that’s becoming more important, especially for landlords). It affects:

• Property value and saleability
• Access to retrofit funding and green finance
• Whether a home can legally be rented, depending on its rating

With government proposals targeting a minimum EPC rating of C by 2028 – 2030 for rented homes, and growing talk of an EPC B target on new builds, the pressure is on. RdSAP 10 helps sharpen the diagnostic checklist and makes it easier to see where a home is losing performance and how to fix it.

What has changed regarding air testing, and how can this improve saleability of properties?

Until now, RdSAP assessments have been based on default air permeability values, based on broad assumptions about age and construction of a property. If you had an older property that had been well retrofitted and sealed, you’d still get penalised with a default leakage figure for that age of property.

RdSAP 10 changes that. If you’ve had an air pressure test (sometimes called a blower door or pulse test), the assessor can now add the actual measured result into the calculation. If that result shows the building is more airtight than assumed, it could improve your EPC rating by 1 – 3 points, and in some cases lift the property by an entire band.

When all said and done, it’s a small investment (typically £200 to £250), but it can make a big difference in marketability. For developers preparing to sell new units, or agents listing modernised homes, having a “verified low air leakage” result becomes a great selling point.

It also gives landlords a practical, evidence-backed route to improve their portfolio’s compliance position ahead of regulation changes.

You can find more about our air tightness testing services at enevo.

What other metrics can significantly improve EPC scores?

Airtightness is a powerful metric, but it’s not the only lever.

The external wall U-value (a measure of how well walls retain heat) also has a substantial impact on EPC scores. If you can improve or even just measure and verify your actual U-values rather than relying on assumptions, you can see substantial SAP score gains.

Other factors that help:

• Roof and floor insulation upgrades
• Modern, high-efficiency heating systems
• Up-to-date glazing and ventilation

The key here is measured over assumed data. If you can provide in-situ testing or credible evidence for building performance, RdSAP 10 will now recognise it, and reward you accordingly.

How can enevo help clients achieve better energy ratings under RdSAP 10?

At enevo, we’re already working with developers, landlords and retrofitters in this area.

Our airtightness testing is fast, fully certified, and includes advice on interpreting and using the results. We also offer:

• Guidance on targeted improvements for maximum EPC uplift
• Support for compliance strategies across large portfolios
• Pre-sale energy performance checks for new developments
• Access to wider building testing services, like thermal imaging, U-value measurement, and retrofit advice

Whether you’re prepping for handover, listing a property, or managing a rental portfolio, we can help you stay ahead of the curve.

Preparing for June 2025 and beyond – what to do now

So, what would we suggest for landlords and building owners?

• Start by reviewing your current EPC stock, especially borderline D/C or C/B properties
• Identify priority buildings that might benefit from specific airtightness testing or U-value measurement
• Build RdSAP 10 criteria into your retrofit plans or development appraisals now

Those who prepare early will not only avoid compliance headaches but could benefit from a stronger sales narrative and improved asset value.

enevo are experts in building compliance, sustainability and built-environment testing and certification.  We’d be happy to chat through your specific portfolio or project and help you make the most of the new RdSAP landscape.  Look at our wider compliance services, air tightness testing page or contact us if you’d like tailored advice.