Retrofit assessment: the PAS 2035 home survey, step by step

Why every funded home gets one

The Warm Homes: Local Grant requires every upgrade to comply with the latest PAS 2035 guidance, currently PAS 2035:2023. The guidance’s glossary describes PAS 2035 as a specification for “whole-house” retrofit: an approach that considers the requirements of the entire building, technically and in terms of things like occupant comfort, rather than fitting single measures in isolation.

The point is to avoid the problems single-measure schemes sometimes caused, such as insulation that traps moisture or a heat pump sized without regard to heat loss. Lessons from earlier schemes, and the late discovery of non-compliant work when installations were only checked at the end, are why the Warm Homes: Local Grant puts lodgement and quality checks throughout the process.

The people involved

What happens on the day

The assessor will want to see every part of the home that matters for energy: walls, windows, doors, the loft if you can reach it, floors, the heating system and hot water, and any signs of damp or ventilation problems. They will also ask how you live in the home: which rooms you heat, when you are in, and whether cost stops you heating it properly. That last question matters. The guidance recognises that many households on low incomes underheat their homes, and expects coordinators to tailor advice so it reflects how you really use energy.

What to have ready

• Access to every room, the loft hatch and the boiler or heating controls
• Recent energy bills, if you have them
• Any certificates for earlier work (insulation guarantees, a previous EPC, boiler service records)
• A list of problems you have noticed: cold rooms, draughts, condensation, mould

From assessment to package

After the survey, the retrofit coordinator designs a package aimed at the largest bill saving for the money, within the caps (up to £16,600 for energy performance and £16,600 for low carbon heating per home, averaged across the council’s project). The guidance’s aspiration is EPC band C “wherever possible within the cost caps”. Where that is not possible, upgrades can still go ahead: fuel-poor households should not be excluded because their home is hard to treat.

The guidance also asks coordinators to prepare an alternative package in case a quote for a particular measure comes in too high, and to consider a medium-term improvement plan for the home.

RdSAP 10 and your EPC

EPCs for existing homes are produced with the Reduced data Standard Assessment Procedure. A new version, RdSAP 10, launched on 15 June 2025 and replaced RdSAP 2012. Every pre-retrofit assessment after that date, and the post-retrofit assessment that follows, uses RdSAP 10. Homes assessed before 15 June 2025 can be completed under the older method, with a new RdSAP 10 EPC lodged on the government register afterwards.

Quality checks after the work

• A TrustMark PAS 2035 project is created for every home within four weeks of the council’s batch being approved.
• A measure guarantee must be in place before work starts.
• Every measure is lodged in the TrustMark data warehouse by the retrofit coordinator, and the project is closed within six weeks of the work finishing.
• The home gets a new EPC.
• Councils can fund aftercare so you know how to use new technology, and follow-up visits for homes with a new heat pump.

Retrofit assessments outside the grant

If you are paying for work yourself, you can still ask for a PAS 2035-style whole-house assessment from a TrustMark-registered retrofit professional. It is not required for every self-funded job, but it is the same logic the grant follows: understand the whole home before choosing measures. How to check an installer.