The newest version of Reduced Data Standard Assessment Procedure (RdSAP) 10 is launching on 15th June 2025. This new version, the first major overhaul in years, is going to change how EPCs are calculated, interpreted, and used in the property market. The goal is simple: less reliance on assumptions, more focus on actual building details. Here’s what’s changing and why it matters:
1. Windows Now Measured Individually
Previously, assessors often estimated window areas based on property type and age. With RdSAP 10, each window must now be measured individually — including height, width, frame material, glazing type, and any special features like low-emissivity coatings.
Why it matters: This results in far more accurate calculations of heat loss and solar gain. Homes with extensive glazing, mixed window types, or high-performance glass will finally see that reflected in their EPC scores.
2. Wall Insulation Thickness: Precision in 25mm Steps
Insulation quality and depth used to be a vague entry. Now, assessors will log wall insulation thickness in 25mm increments, or use actual measured values when known. They can also record partial coverage and specific insulation types.
Why it matters: Homes with professionally installed cavity or external wall insulation will benefit from more realistic EPC ratings — a win for retrofit-conscious sellers.
3. Roof and Floor Insulation Upgraded
- Loft insulation entries now require both thickness and coverage.
- Flat roofs must declare insulation status and type.
- Floor insulation is logged in greater detail, based on its method and coverage.
- Why it matters: More accurate EPCs, especially for properties with recent or hard-to-see upgrades, like suspended floors or retrofitted loft spaces.
4. Lighting Efficiency is Now Counted Precisely
Instead of a simple yes/no on energy-efficient lighting, assessors now input the proportion of efficient bulbs (like LEDs or CFLs) used in fixed lighting.
Why it matters: This gives more weight to lighting upgrades and offers a more realistic picture of ongoing energy use.
5. New Age Band M for New Builds
A brand-new Age Band M is being introduced for homes built:
- From 2023 in England, Wales, and Northern Ireland
- From 2024 in Scotland
Why it matters: This change acknowledges that modern new-builds are built to higher thermal standards and should be evaluated accordingly. It’s especially valuable for agents working with developers or in areas with lots of new housing.
6. Renewables and Tech Finally Count
RdSAP 10 now properly accounts for a wide range of modern low-carbon technologies, including:
- Photovoltaic diverters and battery storage
- Hybrid and renewable heat pumps
- Mechanical Ventilation with Heat Recovery (MVHR)
- Smart heating controls
- Air pressure test results
Why it matters: Homes with renewables or smart tech often didn’t get much credit under RdSAP 9. Now, these investments can positively affect EPC scores — and your ability to market them.
7. Ventilation, Air Tightness & Comfort
RdSAP 10 introduces data fields for Mechanical ventilation systems (like MVHR) and Air Pressure tests for airtightness.
Why it matters: This allows for a much clearer understanding of how a property manages air flow, heat retention, and indoor air quality — all of which influence energy efficiency and comfort.
What This Means for You:
- EPCs will become a more powerful tool — with greater detail and accuracy, you can better position upgraded properties.
- Retrofitted features will finally be reflected in EPC ratings — making that new insulation or battery storage a bigger part of the value conversation.
- More buyers will use EPCs as a decision-making tool — especially with rising energy costs and net zero goals in focus.
This is a prime opportunity to:
- Re-educate sellers on the importance of EPCs, and the need to collate evidence for the DEAs to ensure the EPC is as accurate as possible (e.g. building control completion certificates, guarantees for cavity wall insulation, loft insulation, double glazing etc)
- Highlight hidden value in homes with recent upgrades
- Work with us to ensure data accuracy and speed of turnaround
- You could suggest to clients with older EPCs or recent retrofits to get a fresh assessment under RdSAP 10 — it could significantly improve the rating and strengthen your sales narrative.
RdSAP 10 goes live on 15th June 2025. Make sure your team, your clients, and your listings are ready. Any questions please contact us.