RdSAP10 is live: June 15, 2025. Here we discuss what it means for Building Compliance Testing
This marks a major leap forward in energy assessment standards with the official launch of RdSAP10. This update to the Reduced Data Standard Assessment Procedure (RdSAP) introduces a more rigorous and accurate methodology for generating Energy Performance Certificates (EPCs), especially for retrofit and social housing stock.
At Building Compliance Testing, we’re already implementing these changes and are here to guide you through what they mean in practice—backed by insights by the key Accreditation Bodies, ECMK and Elmhurst Energy.
🔍 Key Technical Updates in RdSAP10
1. Window Measurements & Orientation
Assessors must now measure each window and record its orientation and location, including alternative walls. This improves solar gain calculations and thermal modelling. According to Elmhurst, this change eliminates previous assumptions and enhances the granularity of data collected.
For a semi-detached house with an extension, this adds about 20 minutes; for flats, even less.
2. Room-in-Roof Data Collection
This is now more detailed but will rarely affect social housing. Where insulation can’t be evidenced, no extra work is needed. Elmhurst notes that this change ensures better representation of non-standard constructions, which were previously under-assessed
3. Ventilation Features
Assessors now record:
- Blocked chimneys
- Passive vents
- Extract fans
- Draught lobbies (via site notes/photos)
This supports improved indoor air quality assessments. ECMK’s updated Smart EPC Survey App now includes fields for these features, streamlining data entry
4. Intermittent Extract Fans
These are now excluded from assessments. However, decentralized filterless fans (e.g., Environvent Infinity) are still noted. Elmhurst confirms this change reduces unnecessary complexity in ventilation scoring
5. Lighting
The process is now simpler:
- Most homes use CFL/LED bulbs.
- Down-lighters are easier to count.
- Where no bulb is present, a CFL is assumed.
This aligns with modern lighting trends and reduces ambiguity in assessments
6. Alternative Walls & Flat Corridors
Only doors are now excluded from alternative wall calculations. With just two walls per building part required, this reduces the need for complex extensions. Elmhurst highlights this as a time-saving improvement that also boosts accuracy
7. Hot Water Cylinders (HWC)
Where labels are present, assessors record actual size and heat loss. This applies to fewer than 50% of properties, so the impact is minimal. ECMK’s updated software supports this with automated prompts
8. Smart Meters
Assessors must now check for:
- Digital displays
- Export capability (usually via button 6, A, or B)
This supports better energy monitoring and aligns with the smart home movement
9. Photovoltaics (PV) & Batteries
Considered previously quite rare, as we strive for net-zero, these technologies are on the up. When present, they must be recorded. Elmhurst notes that RdSAP10 is now better equipped to handle renewable tech, ensuring accurate EPCs for modern homes
10. Addendums
- Addendum 15: Tick for every input unless PV is installed.
- Addendum 18: Tick for party walls.
These are quick administrative steps with no significant time impact.
🛠️ What This Means for You
For clients and housing providers, RdSAP10 means:
- More accurate EPCs
- Inclusion of air tightness test certificates and results
- Better data for retrofit planning
- Minimal disruption during site visits
For assessors, while there’s a slight increase in data collection time, the benefits in precision and compliance far outweigh the effort. ECMK and Elmhurst have both released updated apps and training resources to support a smooth transition
✅ Ready for RdSAP10?
RdSAP10 Is Live: What It Means for Building Compliance Testing. At Building Compliance Testing, we’re fully trained and equipped to deliver assessments under the new RdSAP10 framework. Whether you’re planning a retrofit project or need updated EPCs, we’re here to help you stay compliant and energy-efficient.
📞 Contact us today to schedule your assessment or learn more about how RdSAP10 affects your property portfolio.