/ Home & Energy

Can we rely on cavity wall insulation advice?

Cracked exterior wall

Our investigation into cavity wall insulation companies invited eight of the biggest names in insulation into our undercover rented home – and the findings suggest that you can’t always rely on their advice.

I’d never discourage people from getting cavity wall insulation (CWI) installed in their homes – for most houses it’s a great idea and you could save about £110 a year on your energy bills.

But our investigation isn’t about whether insulation will fit in your walls, it’s about whether it might give you damp – and a large bill to get rid of it.

For some homes it’s just not suitable. We rented a house in an unsheltered location that was exposed to high levels of wind driven rain and had cracks in the rendering. The combination of all this meant our expert said the house was at increased risk of developing damp from CWI.

Our undercover findings

Posing as a customer, we asked eight companies, including some big names (such as Tesco, Npower and Marks & Spencer) to assess our ‘home’.

None of the eight assessors warned us of potential damp problems if we’d had CWI installed. One told us our house ‘wasn’t really exposed’. In fact it was on top of a hill with no shelter between it and the sea.

No assessor checked the internal walls for evidence of damp – although some asked our researcher, we think they should have checked the walls themselves. And only two bothered to measure the house fully to calculate the amount of material we needed – the rest seemed to guess by looking.

Despite one assessor stating that the price didn’t change no matter who did the work, the cheapest quote was £99 and the most expensive was £379.

One company – the Mark Group – sent assessors round to quote prices for its own company as well as Tesco, Marks & Spencer and Npower as it does the work on their behalf. The prices differed to the tune of £100 depending on which brand our researcher opted for. The price is set by the brand, but all provided the same job using the same materials, as the same company would have done the work for all the brands.

See more of our findings in our undercover video:

Industry needs to make improvements

We’ve highlighted our concerns to the companies involved and the National Insulation Association that all these companies, or their representatives, are members of.

We want them to improve training and monitoring for their assessors so that consumers are better protected from having work done on their home that potentially could have costly consequences if it’s unsuitable.

Our challenge to the big energy companies, particularly, is to put changes in place quickly so that their customers feel reassured that they can get good advice. So come on industry – make the improvements and tell us here!

And of course, if you’ve had cavity wall insulation, let us know your experiences – good or bad.

David says:
10 December 2012

Fast forward 3 months and its clear from my own investigation that CWI should never have been installed.
The cavity was blocked with rubble above the DPC almost entirely – anyone checking pre-installation could have seen that, on top of the damp issues evidenced within the house. Neighbours confirmed ass much.
CIGA inspection said the outer wall was letting water through… mainly through the holes drilled by the original installer and inadequately patched!

Pauline Saunders says:
3 July 2014


Please read the comments I have posted on line – I know it will do the trick for you.

Good Luck



Cracks have appeared after cavity wall insulation was done, particularly where the company drilled too close to windows in an area with vertical and horizontal bricks of different types. CIGA claims there is no problem, but I don’t believe them. I have read others’ remarks that claim CIGA generally says the problems were pre-existing even if they aren’t. Any information?

Helen says:
2 February 2014

We had cavity wall insulation and I can say I wish to god I had not had it done,we have suffered with mould ever since,it is driving me mad,I have to go around regular with bleach cloth cleaning it off the walls,worst days work we ever did having that done.

Pauline Saunders says:
3 July 2014


Please read my message which I have just posted.

Good Luck!!!!!

Pauline Saunders says:
19 February 2014

We had Mark Group install cwi to our property 2010 – WHAT A MISTAKE, having huge problems trying to get them to rectify the problem with damp issue – CIGA are now involved. Four houses either side of mine, all in exposed sites on a hill with no protection from the element and in a high exposure zone 3/4 are having even worse problems than us. We know Mark Group installed 2 of the properties and are investigating he installers of the other 2.

The cavity wall was never surveyed for rubble, my husband today removed a brick and found loads of rubble.

We are prepared to go to the small claims court to get justice – we are treated like dirt and ignorant idiots by the huge Mark Group.

Pauline Saunders says:
3 July 2014

I am writing an update here in the hope that other people who are having problems with Mark Group will read and follow my advice.

If you have a grievance against Mark Group contact the BBA (British Board of Agrement) online and make a complaint on their site which is quite simple – complete a form and send corroborating evidence to the BBA.

They will carry out an inspection and if in agreement with you that the Mark Group did not carryout an adequate initial survey they instruct Mark Group to rectify the problem.

Mark Group are TERRIFIED of the BBA and will IMMEDIATELY GIVE IN as they could loose their licence to operate!!!!!

I promise you it worked for me and will work for you!!!!!!!

David Andrew says:
4 July 2014

Would be interesting to know how the CIGA would react to this – they were totally dismissive of what we could plainly see and evidence as being wrong with the wall from the start.

Pauline Saunders says:
5 July 2014

I informed CIGA about the BBA report, and they were non-committal – I could not get any comments out of them!!!!!!! CIGA are a waste of space.

However, I do believe BBA won’t let the matter drop and will deal appropriately with CIGA.