How Failed CWI Is Identified and What Lenders See
A mortgage valuer instructed by a lender will typically note damp staining or rising damp on internal walls, which may be accompanied by mould growth, efflorescence (white salt deposits) on external brickwork, or evidence of condensation. In properties known to have had CWI installed, these signs are frequently associated with blown or failed insulation. The valuer may note the issue on their report and recommend a specialist damp survey, which will delay or pause the remortgage until the cause is established and a remediation solution is proposed.
A specialist damp surveyor can confirm whether the CWI is the cause of the dampness using a range of diagnostic techniques including borescope inspection through the drill holes, moisture profiling of the wall and thermal imaging. Their report will identify whether the insulation has become saturated (referred to as "blown"), whether it has slumped and left unfilled voids, or whether contaminated material has caused water bridging across what was previously a dry cavity. The report will recommend either extraction of the insulation or, in less severe cases, targeted remediation.
Lenders are also concerned about the BBA (British Board of Agrément) certificate for the installed insulation. Many CWI installations carried out under government schemes were covered by CIGA guarantees, which run for 25 years from installation. Where the installation has failed within the guarantee period, a remediation claim can be made against the CIGA guarantee. Evidence that a claim has been submitted and accepted, and that remediation is underway, can be sufficient for specialist lenders to proceed.
CWI Removal Costs and the CIGA Guarantee
Extraction of failed cavity wall insulation is a specialist process carried out by certified contractors. It involves drilling larger extraction holes in the outer wall, using a high-powered vacuum to remove the wet or damaged insulation, drying the cavity and then re-filling any extraction holes. Costs typically range from £1,500 to £4,000 for a standard semi-detached house, depending on the size of the property, the type of insulation and the extent of the problem. This is a significant expense that many homeowners feel they should not have to bear given the insulation was originally installed (sometimes without their request) under a government energy efficiency scheme.
The CIGA guarantee scheme provides recourse for homeowners where insulation installed by a CIGA member company has caused damage. CIGA operates a mediation and claims process, and where a valid claim is established, remediation should be arranged at no cost to the homeowner. The process can be slow, and lenders are not always willing to wait for a CIGA claim to be resolved before making a lending decision. However, a specialist broker can often negotiate with lenders to proceed with a retention condition, releasing funds on completion of the CIGA-funded remediation.
Where CWI was installed under a Green Deal arrangement or a government Energy Company Obligation (ECO) scheme, additional recourse routes may be available through the original scheme administrators. Homeowners who believe they were mis-sold CWI should seek legal advice, as successful claims against installers and scheme operators have resulted in compensation for remediation costs and consequential damage.
