What Changed
On 15 June 2025, the UK introduced RdSAP 10, the most significant update to domestic energy assessments in over a decade. The key shift: documentary evidence is now mandatory for accurate EPC scores.
- Evidence-based hierarchy: assessors must prioritise actual evidence over assumptions
- No documents = default values: without proof of upgrades (insulation, glazing, heating), assessors use conservative defaults that lower EPC scores
- Heating system specs required: model numbers, manufacturer data, and smart control evidence now expected
- Air pressure test results: can be included if documentary evidence is available
- Insulation thickness + thermal conductivity: detailed records required where supported
- Cylinder size and heat loss: must be evidenced with documentation
Previously, if details couldn't be verified, assessors made reasonable assumptions. Under RdSAP 10, no evidence means lower efficiency ratings, even if upgrades were completed.
Why Installers Care
Heat pump installations often depend on achieving a specific EPC rating for grant eligibility (e.g., BUS) or MCS sign-off. If the homeowner's EPC drops due to missing documentation, the project can stall or require rework.
Callback risk: if the EPC doesn't reflect recent upgrades, installers may need to revisit the property to gather missing evidence.
Grant eligibility: BUS applications require a valid EPC. If evidence is missing and the score is lower than expected, homeowners may not qualify.
MCS sign-off: heat pump design calculations rely on accurate U-values and heat loss data. Without evidence, assessors use defaults that may not reflect the property's true performance.
What's needed for accurate RdSAP 10 assessments:
- Insulation records: thickness, material, installation date
- Glazing certificates: FENSA, window specs, U-values
- Heating system details: boiler/heat pump model, efficiency rating, installation date
- Building regs sign-offs: for extensions, loft conversions, or structural work
- Air pressure test results: if available (can improve airtightness score)
- Hot water cylinder specs: size, heat loss rating (if documented)
If these documents are photographed during the survey, they're available for the assessor to reference. If they're not captured on the day, the homeowner has to dig them out later, which delays the EPC.
What to Capture on Site
For heat pump installations, surveyors should photograph relevant documents during the site visit to reduce follow-ups and ensure accurate EPC scores under RdSAP 10:
- EPC report (if available): shows current rating and assumptions used
- Building regs certificates: extensions, loft conversions, structural work
- Window/door certificates: FENSA, Certass, U-values, installation dates
- Insulation records: invoices, specs, thickness, material (loft, cavity, solid wall)
- Heating system documentation: boiler/heat pump model, efficiency, installation date
- Air pressure test results: if available (can improve airtightness rating)
- Hot water cylinder specs: size, heat loss, model number
- Smart heating controls: photos of installed kit, model numbers
If homeowners have these documents ready on the day, they should be photographed during the site visit. This ensures the assessor has what they need for RdSAP 10 compliance without follow-up requests.
Timeline Impact
RdSAP 10's evidence requirements mean EPCs may take longer if documentation isn't ready. Typical turnaround expectations include:
- Documents ready on survey day: EPC can be delivered promptly, project moves forward
- Documents missing on survey day: homeowner sources them later, EPC delayed, project stalls
- Documents never found: assessor uses default values, EPC score may be lower than expected, grant eligibility at risk
By photographing available documents during the site visit, follow-up requests can be reduced and EPCs can be completed more efficiently.
Timeline Impact
RdSAP 10's evidence requirements mean EPCs take longer if documentation isn't ready. Here's how it affects project timelines:
- Documents ready on survey day: EPC delivered next morning, project moves forward
- Documents missing on survey day: homeowner sources them later, EPC delayed, project stalls
- Documents never found: assessor uses default values, EPC score may be lower than expected, grant eligibility at risk
By photographing available documents during the site visit, we reduce follow-up requests and keep EPCs on track for next-morning delivery.
Related Resources
For more on RdSAP 10 evidence and compliance: