If damp, mould or other problems appear after insulation is fitted, contact the installer first, then the guarantee provider, and only then the scheme bodies and dispute services. Keep a record of everything, because each step asks what the step before it said.

This guide follows the order set out by the Energy Saving Trust for cavity wall insulation and by Ofgem for work done under the Energy Company Obligation (ECO). It applies whether you paid for the work yourself or had it free under a scheme.

What should I gather before I call anyone?

Ofgem's complaints guidance suggests having these ready:

  • what was installed, and when;
  • the installer's name and contact details;
  • the guarantee or warranty certificate, if you have one;
  • dated photos of the problem, and notes of when it started.

If the work was done under ECO4 or the Great British Insulation Scheme, look for a letter from Ofgem with a Unique Measure Reference. GOV.UK says every organisation involved in checking that work will quote it when they contact you, which is how you can tell a genuine call from a scam.

Is the insulation actually the cause?

Not always. GOV.UK's guidance on damp and mould says condensation is the most common form of damp, and that water can also get in through defects in the building or rise from the ground in older homes. The Energy Saving Trust says insulation can be the cause, but so can poor maintenance, and if it is maintenance the installer and guarantor will not pay. If you are not sure which you have, National Mould Experts explains the usual causes of mould and how to tell them apart.

GOV.UK also says people with existing health conditions, and children, are most at risk from damp and mould, so do not wait for a complaint to finish before getting the moisture dealt with.

Step 1: what should I ask the installer?

The Energy Saving Trust says the installer should discuss the problem, revisit, and work out whether the original survey or the installation is part of the cause. If it is, they should fix it, or remove the insulation if that is what it takes. Ask them:

  • What did the pre-installation survey record about the wall, its exposure to rain and its condition?
  • Which material was used, and was it suitable for this wall?
  • Were any vents, airbricks or trickle vents blocked or removed?
  • What will you do, by when, and will you confirm it in writing?

Step 2: when do I go to the guarantee provider?

If the installer will not help or no longer trades, check your paperwork for the guarantee. The Energy Saving Trust says cavity wall insulation should come with a 25-year guarantee from the Cavity Insulation Guarantee Agency (CIGA) or an independent insurance-backed guarantee, and that CIGA should help resolve the issue under its terms. Ofgem notes some guarantee providers prefer you to contact them at the same time as the installer. Insulation Crisis Help has a fuller walk-through of making a claim on a CIGA guarantee.

Step 3: what if the work was done under ECO4 or GBIS?

GOV.UK says there are quality issues with some solid wall insulation fitted through government schemes since April 2022:

  • External wall insulation: Ofgem is arranging checks. You may be contacted by Ofgem, by TrustMark or by the certification body that oversees your installer. Accept the check. You should not be asked to pay, and if the work is faulty the installer will be asked to fix it.
  • Internal wall insulation: GOV.UK says fewer issues have been found and no action is needed unless you have a problem.
  • Questions: Ofgem's helpline is 0808 169 4447 (Monday to Friday, 9:30am to 4:30pm), or email ECOhelp@ofgem.gov.uk.

Insulation Crisis Help explains what the free Find & Fix audit involves.

Step 4: where can a complaint go next?

Ofgem's ECO complaints guidance lists these, after the installer and guarantor:

  • TrustMark, through its own complaints process, as most ECO work needs a TrustMark-registered installer;
  • the scheme provider for the measure, such as CIGA, the Installation Assurance Authority (IAA), GGF or MCS;
  • the Centre for Effective Dispute Resolution (CEDR), the ombudsman for RECC, MCS, CIGA, IAA and GGF matters;
  • Citizens Advice and your local Trading Standards; in Scotland, Energy Advice Scotland.

If the installer or guarantor refuses and you think they are wrong, the Energy Saving Trust suggests an independent assessment of the walls by a building surveyor, which you can find through the Royal Institution of Chartered Surveyors (RICS).

What if the insulation has to come out?

The Energy Saving Trust says removal should be done by a specialist cavity wall insulation removal company. Our cavity wall insulation removal page explains what that involves. Before any new insulation goes back in, the cause of the damp needs to be fixed; our guide on which insulation to do first covers the repairs to make before insulating.

Sources, checked 2 October 2026: Energy Saving Trust, cavity wall insulation; Ofgem, ECO complaints process; GOV.UK, what to do if you have poor quality wall insulation and health risks of damp and mould.

Get free quotes from local insulation specialists: tell us about your home and we will pass it to Better Home Hub, which looks for up to 3 specialists who cover your area. It is free and you choose whether to go ahead.