The most significant update to domestic energy assessments in over a decade is here. RdSAP 10 shifts the focus from broad assumptions to a detailed, evidence-based approach. This guide visualizes what you need to know.
Previously, EPCs relied heavily on default values due to software limitations. RdSAP 10 demands a more granular look, requiring specific measurements and documented proof to build a true picture of a property's energy performance. This change empowers accurate, reliable assessments.
The new methodology requires assessors to collect significantly more data on-site. Here are the key areas of change where detailed observation is now mandatory.
Every single window must be measured. Assessors now record width, height, orientation, frame material, glazing type, gap, and age for all windows, plus features like shutters.
New detailed inputs are required for Room in Roof constructions and heated basements, including specific measurements and construction types to apply more accurate U-values.
Exact thickness of wall, roof, and floor insulation must be recorded in mm. Alternative wall types for extensions can now be specified to improve assessment accuracy.
All flue types must be documented, including open flues, boiler flues, and blocked chimneys. All mechanical ventilation systems and extractor fans must also be recorded.
The assessment moves beyond fittings to require a count of individual light bulbs, with a percentage breakdown of bulb types (e.g., LED, CFL).
Detailed data for heat pumps (SCOP) and Solar PV (pitch, orientation, shading) is now required. Modern tech like battery storage and PV diverters are also included.
To avoid conservative default values, providing documentary evidence is crucial. The more high-quality evidence supplied to the assessor, the more accurate the EPC rating will be. This chart shows the relative impact of providing key documents.
An accurate, evidence-backed EPC is more than a certificate. It’s the foundation for a smart, long-term decarbonisation strategy, turning compliance into a tangible, value-driven plan.
Detailed Data Collection
Accurate RdSAP 10 EPC
Strategic Retrofit Plan