Chimneys, open fires and wood burners with ECO4 insulation and boilers: a UK household checklist (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 still have a chimney, an open fire, a gas fire or a wood burner. When insulation goes in or the boiler changes under ECO4, the way air moves through the house can change too, so it is worth thinking about how your fire and chimney fit in. This checklist is general information from ApplyFreeBoiler.uk, a heating and insulation installer in Bury. It does not replace the surveyor's assessment or advice from a qualified chimney or appliance engineer, and it does not guarantee funding.

1. Tell the surveyor about every fire and chimney

Mention any open fire, gas fire, wood burner, multi-fuel stove or chimney you use, and any that are blocked up or capped. The surveyor needs this to plan insulation and ventilation safely.

2. Fires need air to burn safely

Open-flued fires and stoves need a supply of fresh air. Insulation and draught-proofing reduce draughts, so ask the installer whether the home still has enough ventilation for each appliance and never block a fixed air vent that serves a fire.

3. Air bricks and vents

Air bricks and wall vents are there for a reason. Ask the installer how they will keep them clear when they fit cavity, internal or external wall insulation, and do not cover them with furniture or boards afterwards.

4. Chimney breasts and internal wall insulation

If you are having internal wall insulation, ask how the installer will deal with the chimney breast and the fireplace opening, and whether this affects your ability to keep using the fire.

5. Sweep the chimney before winter

If you use a chimney, have it swept by a qualified sweep, particularly before the first winter after your upgrade. A blocked flue can let fumes into the home.

6. Old back boilers

Some older homes have a back boiler behind a gas fire. If your boiler is being replaced under ECO4, ask what will happen to the old back boiler and fire, and how the opening will be made safe.

7. Fit and test carbon monoxide alarms

Any room with a fuel-burning appliance should have a working carbon monoxide alarm. Test it regularly, and if it sounds, open windows, turn the appliance off, leave the room and call the gas emergency number.

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.