Holes in insulation advice, finds Which? probe

A Which? undercover investigation suggests you can’t always rely on assessors from cavity wall insulation companies – and following poor advice could leave you with damp. 

Which? secretly filmed visits from cavity wall firm representatives that were invited to assess our rented property for suitability. We found evidence of misleading claims, a lack of thorough checks and a huge range of quotes for the work.

Take a look at our short undercover video to see examples of poor advice.

Cavity wall insulation not suitable

For most homes, cavity wall insulation (CWI) is a great idea and can save you about £110 a year on your energy bills, but some properties are at risk from damp if they have CWI. This is because of a combination of risk factors. Our rented property was deemed not suitable by an expert chartered surveyor because it was in an extremely wet and exposed area and had cracks in its external walls. In these circumstances, CWI can transfer moisture from the outside to the inside of a property, resulting in damp.

Despite this, none of the eight assessors invited to the house identified the risk of damp; all said it was perfectly suitable. And all failed to carry out the checks that Which? deems essential to assess suitability.

Only one assessor inspected external walls thoroughly to identify cracks, just one bothered to look at the boiler and surrounding ventilation to check if insulation would impact on safety, and none inspected the inside of the property to look for signs of damp. Some asked the householder (our undercover researcher) about damp, but we think that assessors should check this themselves.

An assessor from insulation chain the Mark Group told us our home was ‘not really exposed to anything’. In fact our property was on the top of a hill with nothing between it and the sea. Mark Group tells us that a more thorough inspection would have been carried out and all relevant paperwork filled in had our researcher said they wanted to go ahead and purchase CWI.

Have you had cavity wall insulation installed? Let us know your experiences – good or bad – on Which? Conversation.

Price differences for wall insulation

In an effort to persuade our researcher to sign up, A&M Insulations’ assessor also claimed that the price wouldn’t change no matter who she chose to use. But we were quoted price differences of between £99 and £378 in our eight visits.

Two assessors from Mark Group – who visited the property to quote for work on behalf of Mark Group, Npower,Tesco and Marks and Spencer – gave quotes varying from £149 to £249 despite assessors recommending the same work and materials for each brand. Mark Group said the individual brands set the prices.

Misleading claims from installer

Which? also found evidence of scare tactics to try and push a sale. An assessor from A&M Insulations stated that polystyrene beads (as opposed to the fibre material he recommended) used by rival firms could release ‘toxic’ fumes if there was a fire.

In fact, when installed correctly in a suitable property, beads are not toxic and present no danger to homeowners.

Advice on installation

Our guide to cavity wall insulation gives advice on ensuring your property is right for it. For advice on other ways to make your home energy efficient, see our guides to loft insulation and using energy saving lightbulbs,.

Which? members can read the full article ‘Insulation: the price gap, the advice gap’. If you’re not a member, subscribe to Which? magazine now to try three issues for just £3.