Homes with extensions and ECO4: questions UK households ask (guide 2026)

Guide by ApplyFreeBoiler.uk (Reliant Energy Solutions Ltd), a heating and insulation installer in Bury, Greater Manchester. We are not the government, Ofgem or an energy supplier.

Many UK homes have been extended over the years, with a kitchen, a side extension, a garage conversion or an extra bedroom added on. An extension is often built differently from the original house, with newer cavity walls, a flat or pitched roof of its own and sometimes separate heating. That raises a few common questions when a home with an extension is assessed for ECO4. This guide covers questions households commonly ask. It is general information from ApplyFreeBoiler.uk, a heating and insulation installer in Bury. What is recommended depends on the survey and the scheme rules at the time. This page does not guarantee funding.

1. When it was built

Tell the surveyor roughly when the extension was built, as newer extensions often have different walls and insulation from the original house.

2. Wall types

Say whether the extension walls look different from the main house, for example rendered, newer brick or timber cladding.

3. Its roof

Mention whether the extension has a flat roof, a pitched roof or a roof window, and whether there is any loft space above it.

4. Heating in the extension

Say whether the extension has radiators on the main boiler, electric heaters or underfloor heating, and whether it stays warm.

5. Your boiler

Say roughly how old your boiler is, where it is located and whether it was moved when the extension was built.

6. Paperwork

If you have building control sign-off or plans for the extension, keep them handy in case they help the surveyor.

7. Clear access

Clear space around the boiler, meters and any loft hatch before the survey visit.

8. Check funding and local figures

See ECO measures by council on ApplyFreeBoiler.uk, built from DESNZ Household Energy Efficiency statistics, to see how many ECO measures have been installed in your local authority area. Use the ApplyFreeBoiler.uk eligibility check to see whether an ECO4 heating or insulation pathway may be available for your home in England, Scotland or Wales. ECO4 is due to close on 31 December 2026.