What to show your EPC assessor: evidence for insulation, heating and improvements
A practical way to prepare for a home EPC survey when useful energy-saving work is hidden from view.
An EPC is based on what the assessor can establish
A domestic Energy Performance Certificate describes a home's energy performance using information gathered by an accredited assessor and an approved calculation method. Some facts are obvious on a visit: the heating controls can be seen and a loft may be accessible. Other improvements, such as cavity-wall insulation or insulation below a floor, may be concealed. If an assessor cannot verify a feature, the method may require a standard assumption based on the age and type of the building. That can make a genuine improvement invisible in the certificate. The government's domestic EPC guide explains why supporting evidence matters.
Build a small evidence file before the visit
Gather dated installation certificates, invoices, guarantees, building-control records or clear photographs showing work before it was covered. Match each item to the part of the property it describes. For a loft conversion, for example, distinguish the original roof from the converted section. For cavity, internal or external wall insulation, identify which walls were treated. Include details of replacement windows, hot-water cylinders, boilers and heating controls where available. A product brochure without proof that the product was installed in this home may not be enough. The assessor decides what evidence the approved method allows them to use; the documents support the survey rather than replace it.
Make the property easy to inspect
Arrange safe access to the loft hatch, boiler, meters and any relevant heating controls. Tell the assessor about extensions, unusual construction, rooms above unheated spaces and recent changes. Do not open up walls or remove finishes for an EPC without discussing it first. The assessor is not expected to take unsafe risks to inspect concealed work. If the home contains a flat above commercial premises or several building phases, explain the layout in advance so the correct dwelling is assessed. Our domestic EPC booking page lets you provide the address and property details before arranging a visit.
Treat recommendations as a starting point
An EPC can suggest measures such as insulation or heating improvements, but its estimated costs and savings are modelled figures, not a contractor's quotation or a promise of a particular future band. Check whether a proposed measure is suitable for the building, whether consent is needed and how it interacts with ventilation and moisture. The government home energy advice service can help you explore options. If you are preparing to sell or let, first read our guide on whether an existing EPC can be reused. Then decide whether a new assessment would usefully record improvements already made.
The useful question to ask before ordering
Ask: what has changed since the last certificate, and what can I prove? A current EPC does not automatically expire because work has been carried out, but an updated assessment may better describe the home. Send the evidence file with your booking enquiry and ask what the assessor will need to check on site. That gives the visit a clear purpose and helps prevent avoidable assumptions.