/ 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.

Pauline Saunders says:
11 June 2015

As an update on this comment – I went on to become a founding member of CWIVA who had enormous successes. We raised a 90 min Parliamentary debate on 3 February 2015, and have gone on to help about 600 victims of botched cavity wall insulation.

Started my own site to carry on the work on CWIVA by founding the free help line
CIVALLI – Cavity Insulation Victims’ Alliance email. The website will be up and running week commencing 15 June 2015.

You can expect a personal, empathetic reply to you problems – run by myself and a few volunteers.

Pauline Saunders says:
12 June 2015

That is a shame as it is a free voluntary site, with no commercial interests whatsoever. I just want to let victims that there is help out there.

I would be grateful if you would reconsider and just leave out the name of the organisation. Please, please?

Could you just remove the name of the site, I think my name might be sufficient.


Pauine Saunders

Morning Pauline, thanks for your comments. We’ve reconsidered your post, and we’ve published it again for you. Sorry about that!

We think it’s an excellent group you’ve set up and wish you all the best in future 🙂

My parents had Cavity w I installed by the Mark Group in 2010. They have had no end of trouble ever since with black mould and penetrating damp. Upstairs and down stairs all over the walls from top to bottom and front to back of the house. Mark Group deny all responsibility. CIGA told my parents that they are not entitled to see the report. However the Mark group sent me it. Why were they not entitled? However it stated ‘not installed to BBA standards’ yet what they sent my parents was that the property is poorly maintained. Utter rubbish! They’re all in it together. 10k worth of damage in a house with no damp previously. This is an open door for botched up scammers due to the power of the industry and green lobby. Also my parents were told it was Govt funded when actually Eon funded it. The Mark Group were still claiming to have Govt funding this year (April) I have the evidence! Lies Lies Lies and still no one challenges this company, ruining lives and all Govt endorsed.

David Andrew says:
2 June 2014

CIGA were a joke, insisted it was down to render cracks when in reality the drilling itself had left holes that water literally dripped from when wet and it was clear the walls themselves had serious bridging above the DPC causing water + mould on the inside walls.
I was “lucky” enough to be able to sort out the bridging myself and got the drill holes patched properly and the render repaired. Hot summer really helped sort it out but I ran a dehumidifier for months to help dry the walls from the inside out.

Yes CIGA are a waste of time. There must be something people can do collectively. It’s so wrong. There will be elderly and vulnerable living in damp conditions without help. It makes me furious.

Pauline Saunders says:
4 July 2014

I agree CIGA are a complete waste of time – go straight to BBA and fill in the complaint form.

Guaranteed Christmas will come early for you!!!!!!!!!

Pauline Saunders says:
6 February 2015

A group called CWIVA Cavity Wall Insulation Alliance has formed to provide free advice to fellow victims of botched cwi.

Read Hansard debate in Parliament 3 February 2015 on this issue – instigated by CWIVA.

We can and will provide empathetic and practical help in you fight for your home to be reinstated to its former cwi condition.

Go online CWIVA for support.

Pauline Saunders says:
11 June 2015

CIVALLI – Cavity Insulation Victims’ Alliance has been formed by Pauline Saunders – founding member of CWIVA – to take over where CWIVA left off.

FREE helpline for victims of botched cavity wall insulation – there are thousands of victims out there desperate for help, that do not know where to turn – suffering from mental and financial problems.

I have helped hundreds of victims as a founding member of CWIVA – and have never failed to succeed in gaining justice for victims and has never, ever given up on a case.

I empathise completely as I too was a victim!!!

brian says:
7 February 2015

It would appear that another Which investigation needs to be carried into this industry. I was tempted by the ‘Green Deal’ funding after moving to a new property and got a quote for a new boiler plus one other improvement which was CWI. The boiler quote came to £2000 and CWI £1000 yet I’m in a 3 bed semi so does that sound right?! I will get £1000 back from the govt plus another £500 for moving in within the last 12 months. Seems to me the CWI quote was over inflated. The company are Green Deal approved etc but do not appear to be giving any guarantee whatsover, not in the quote anyway. Looking at everyones problems here I am not having CWI installed.

brian, I’d suggest simply getting independent quotes for a boiler and insulation from 2 or 3 people and see how they compare with your Green Deal prices.. My guess is they are a bit pricey, but it depends how much work is involved in fitting a new boiler. However if it costs you £1500 after your grant then it sounds a good deal for you, but posibly a bad one for the government (and thus the taxpayer).

brian says:
7 February 2015

Malcolm, thanks for your good suggestion. Yes the deal doesnt seem too bad and the CWI price is not so much a concern but the many problems that could arise after it is installed, possibly several years later. Even with a guarantee it would appear the industry tries to duck its responsibilities from what I have read so far. Its impossible to be absolutely sure its the right thing so having CWI just doesnt seem worth the risk (to me) even if you are paid to have it!

brian, I agree there do seem to be risks with cavity insulation in an existing wall mainly, presumably, because it bridges the outer and inner leaves with the possibiity of allowing any penetrating water to reach the inside. I did not know about this 30 years ago when we had our cavities filled with chopped glass fibre. I’m pleased to report that we have had no problems with damp and it made a big difference to our comfort and heating bills.

Take a look at the Linked In group called “Cavity Clearance Information Exchange”.

I am trying to pull together all of the information available on the subject including possible solutions.

Feel free to details any problems that you are experiencing on the discussion on customers problems.

Pauline Saunders says:
3 March 2015

A group called CWIVA – Cavity Wall Insulation Victims’ Alliance has recently been formed by
3 women whose lives had been made miserable and blighted after the installation of cavity wall insulation which caused severe damp and condensation in their own homes. They were so aggrieved by the way the cwi industry treated them with contempt and ‘fobbed’ them off with any excuses, anything other than admit that they had breached regulations and inserted in properties which were totally unsuitable, such as in exposed sites with south westerly wind-driven rain.
CWIVA have set-up a free help-line for victims, with advice on how to win their cases.

[This comment has been edited to align with our commenting guidelines. We do not allow email addresses to be published – Thanks, mods]

I am due a visit from mark group to install cavity wall insulation, they have assured me my house is suitable and I won’t have damp problems. The guy who carried out the survey seemed to know what he was talking about but after doing some online research and reading lots of negative comments I’m not sure what to do. I appreciate that most of the comments are negative because I assume if you had a good installation you wouldn’t have felt obliged to write any comment at all. Really not sure what to do.
Any advice

Insulating a house and saving energy is a good thing.

However, this assumes that the house is correctly assessed (most are not) material is suitable (growing questions of fitness) and the approved method of installation is adhered to (majority may not be fully compliant).

OK, there is always a risk, but if the job is done correctly in all regards the risk may be leased, but not eradicated (even new build houses are starting to suffer).

Research shows that getting a combination of the factors wrong dramatically increases the risk.

My advice would be to seek professional independent advice from a Chartered Surveyor (I am not one) before risking your home and the biggest investment you are ever likely to make.

I had cavity wall installation installed in my home in Newport. It has caused a condensation/damp problem along an internal wall. The company no longer trades and did not register my property with ciga, so I do not have a guarantee. I did have an inspector out from RIS before they went to the wall, who blamed the problems on my windowsill! I have contacted ciga who have been no help at all. Im at a loss of what to do next!

Hi Deborah,
Your Next Steps ! gather all information and paper work regarding the installation of your property
With this paperwork I should be able advise your going forward.



[This comment has been edited to remove personal contact details in line with our community guidelines. Thanks Mods.]

Pauline Saunders says:
16 August 2016

Hi Deb – I too live in Malpas, Newport and run a voluntary helpline. You must get back to CIGA IF the company was registered with CIGA, they MUST honour the Guarantee. I run a ‘free’ voluntary helpline for victims of botched cavity wall insulation. Put my name on line and you will find me

I am in the process of buying a house and have hit my first real disappointment. I knew that cavity wall insulation was installed in 2011 and is covered by a 25 year CIGA guarantee. Unfortunately the job was done by the Mark Group mentioned above, and they went into administration. Fortunately, the surveyor has found no sign of dampness or poor workmanship, and I have not seen any problems. However, I may never know whether the insulation is as effective as it should be.

When our bungalow was extended 30 years ago we had chopped glass fibre blown into the cavity. It made an enormous difference to the older part of the house – prior to insulation as soon as the coal fire died down the chill began to creep up on us. No problems with damp in all that time and one wall is particularly exposed to the prevailing wind and rain.

You could have thermal images taken to see if the insulation appears uniform.

Thanks Malcolm. I have avoided cavity insulation in my present house because I did not want to take the risk of problems. As you say, there are ways of investigating problems.

I was reluctant to install double glazing in my present home for the same reason, but it has proved faultless. However, I have seen plenty of substandard materials and workmanship when looking to move home.

Guarantees that become worthless if the installer fails have long been a problem with home improvements. I believe the only way to protect against this is to have the guarantee bonded against an insurance policy. This will increase the cost but might be worthwhile as anything can happen over tewnty-five years [although proving it was due to a defect or fault in installation becomes increasingly difficult]. The problem with cavity wall insulation is that it is impossible to take it out and replace it and I expect retro-filling blank spots is well-nigh impossible.

I expect you are right, John, but I’m more concerned about the possibility of dampness than blank spots. The company has done a very neat job and fingers crossed I might be one of the lucky ones. Hopefully a problem would have shown up in four years.

my issue is slighty different to the rest. moved into bungalow lived in by parents previously. did additiiional vent fitting to bathroom which dislodged cw bead insulation to gable end. Also on checking subfloor void found more bead cwi flowed out of cavity wall. Have contacted cwi fitters but should i be able to leave voided areas as they are or not. Gather that company may only agree removal with loss of ciga warranty.If no other issues should i just leave with these voided areas and accept that warranty invalid now anyway.

Houses that are originally built with completely hollow cavity walls are 100% perfect as they are. Nothing must be later on added to the wall cavities of houses that are originally built with completely hollow wall cavities – IT WOULD BE SEVERELY DETRIMENTAL TO THE BUILDING : THE WALL CAVITIES MUST BE LEFT COMPLETELY HOLLOW

Properly installed cavity wall insulation will lower heating costs and reduce environmental impact. Not all homes are suitable, as explained in the introduction, and care must be taken to find competent installers, but many home owners have benefitted.

Loft Boarding Specialist says:
22 October 2021

Great tips! Looking forward to more ideas.