Domestic EPCs in the UK are produced using a government-approved methodology called RdSAP (Reduced Data Standard Assessment Procedure). The latest version — RdSAP 10 — introduces several important changes that may affect your property’s energy rating.

For some homes, the update may result in a higher rating. For others, it could lead to a lower score. The only way to know for certain is to commission a new EPC under the updated methodology.

Key Takeaways

• RdSAP 10 changes how insulation, heating systems, and construction details are recorded.
• More detailed data capture can benefit well-upgraded homes.
• Assumptions are now handled differently, which may reduce ratings for poorly documented properties.
• Older EPCs do not automatically update — you need a new assessment.
• If you are selling or renting, checking your rating under RdSAP 10 is advisable.

What Is RdSAP 10?

RdSAP is the simplified method used to produce EPCs for existing homes. Version 10 updates how assessors collect and input data, with improved accuracy and tighter assumptions.

The update aims to better reflect real building performance, but that also means some properties are now assessed more strictly.

How RdSAP 10 Could Improve Your Rating

• Better recognition of documented insulation improvements.
• More accurate modelling of heating controls.
• Improved treatment of certain construction types.
• Clearer recording of ventilation and extensions.

If your home has had upgrades — loft insulation, cavity wall insulation, modern heating systems — a new EPC under RdSAP 10 may reflect those improvements more accurately.

How RdSAP 10 Could Lower Your Rating

• Stricter assumptions where evidence is missing.
• More detailed recording of extensions and floor area.
• Revised modelling of certain heating systems.
• Better identification of poorly insulated elements.

If previous EPCs relied on optimistic assumptions or lacked full documentation, the new methodology may result in a lower score.

Should You Get a New EPC?

If you are planning to sell, rent, refinance, or upgrade your property, obtaining a new EPC under RdSAP 10 provides clarity.

An updated certificate ensures:

• Your rating reflects current rules.
• Improvements are properly recorded.
• You avoid surprises during a sale or tenancy.
• You understand whether further upgrades are worthwhile.

Local Context: Bristol & BS Postcode Properties

Many homes in Bristol are older solid-wall properties or have been extended over time. RdSAP 10’s improved data capture around extensions and construction types may change how these homes are scored.

If your EPC is several years old, it may not reflect current modelling standards.

Frequently Asked Questions

Does my old EPC automatically update under RdSAP 10?

No. Existing EPCs remain valid for 10 years but do not update automatically. A new assessment is required.

Will RdSAP 10 guarantee a higher rating?

No. It may improve, reduce, or leave your rating unchanged depending on your property’s characteristics and documentation.

How do I know if I should get a new EPC?

If your certificate is more than a few years old or you’ve made improvements, a new EPC under RdSAP 10 provides clarity.

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Want to See How RdSAP 10 Affects Your Property?

If you’re in Bristol or the BS postcode area, book a new domestic EPC to see how your property performs under the updated methodology.