RdSAP 10: is this the biggest change to EPCs since their inception?
Ahead of the approaching release of RdSAP 10 on 15th June 2025, we are busy ensuring all of our assessors are ready for the changes. With the last full-scale changes to the methodology released five years ago, this change is long overdue. The new methodology will bring RdSAP closer than ever to SAP and improve the accuracy of EPCs.
EPCs are increasingly relied on by prospective tenants and purchasers, so producing accurate assessments is vital. Upskilling our teams and giving our assessors the time to be able to collate the additional data is a major priority for us.
First things first: what is RdSAP?
RdSAP stands for Reduced Standard Assessment Procedure and is the UK’s official methodology for assessing the energy performance of existing residential buildings. It is developed by the Building Research Establishment (BRE) and used by all energy assessors to produce EPCs. Non-domestic buildings, such as hospitals and shops, use a different methodology.
RdSAP was introduced in 2005 as a simpler and less expensive approach, when compared to the full SAP calculations (Standard Assessment Procedure), which are is used for new dwellings. It allows assessors to create EPCs combining data collection on site with default values, when the full information is not available.
SAP 10 was launched in 2023 after several delays, and this June RdSAP 10 will be released.
What do the changes mean for you?
Whilst we are working hard in the background making sure we are ready for the changes, the transition for our clients should be seamless. However, due to the increase in data required (as some of the default values will no longer be available), you can expect our DEAs to be onsite a little longer. This increase in data will likely cause a small increase in processing time to produce the final EPC – but it will be worth it!
Ensuring vendors, landlords or tenants are prepared for the visit and have any documentation available for improvements can help to streamline the process and ensure the accuracy of the EPC. Our EPC flyer outlines some of the documentation we may require, but our expert team are always happy to help by phone or email on [email protected]. Please send them any questions you may have about the incoming changes. You can read more about preparing for an EPC here.
What are the changes?
As RdSAP 10 is taking a big step closer to SAP, the main changes are the introduction of values which have defaults within the current version (RdSAP 9.94).
Here is a snapshot of some of the changes and how they might affect the EPC:
Measure all windows. Currently window values are defaulted based on the typical window area for the property age. However, now our DEAs will be required to measure all the windows and collect data on each window.
- Additional data on flues. With heat loss via gaps in a building’s fabric contributing to energy losses, our assessors will now have to count all flues. Currently open chimneys are recorded, but the opening from boiler flues, closed fires, extractors and more will now also all be accounted for.
- Additional options for roof rooms. Additional measurements and considerations will now be accounted for roof rooms within properties. We expect these changes to be particularly good news for mid-terrace properties which have a roof room.
- Photovoltaic diverters and batteries. New EPCs will now have the option to record PV diverters (where electricity generated from solar panels is diverted to the immersion on a hot water tank) and PV batteries (which can store electricity for later use, rather than feeding back to the grid).
- Lighting changes. Low energy lighting is currently considered to be compact fluorescent lamps or LEDs. New recorded data will now separate these figures, whilst also accounting for non-low energy lighting. This will produce an average rating for the lighting efficacy (simply, how much light a light produces for the energy used).
- New age band. Introduction of age band of properties or extensions built from 2023 onwards. Although properties built within the last 10 years still require full SAP, (on construction EPC) it will only effect extensions for now.
- Changes to recommendations. Introduction of recommendations for heat pumps, if appropriate for the property. With the increase in government grants for switching to a heat pump now £7,500, it is their recommended low carbon solution.
These changes mark a major shift for EPCs along with a few other changes. It will affect the grade of a new EPC compared to old ratings, but with a higher level of accuracy it is certainly a positive change.
How can we help?
When these changes are implemented in June, if you require a replacement EPC we would expect a difference in the grade. This might be positive for some but unfortunately negative for others. However, rest assured we are here to help with our EPC advisory service. Whether you are looking to improve your grade or for advice on how changes will affect you, please don’t hesitate to get in touch. Contact us on [email protected] or go to Fourwalls Energy for more information on our services.
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