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Cavity wall insulation? Don’t bother

I’ve had the process done on three occasions in three houses. The loft insulation works; sadly I have logged the difference and found really good savings can be made. In most cases, a 25 per cent saving in energy use is to be had. However, cavity wall insulation is rubbish; it has minimal effect on the heat losses from your house - again I have logged it.
Let’s look at why this is. The problem is that the lagging applicator (I refuse to call him an engineer) never actually fills the cavities because he knows you can’t easily check his work. The only way to see is to either drill loads of holes yourself and look inside the cavity with a bore scope or measure the inside wall temperature with a thermometer and find the cold spots... yes I’ve done it.
The problem lies in the method of application. A man drills 22mm holes all over the outside of your house and using a reverse vacuum cleaner pumps the cavity’s full of insulation. The lagging doesn’t go very far into the cavity unless it is very wide and has no debris in it. So it doesn’t work if the house is old - brilliant.
This weekend I was in the loft spaces lagging the last of my house, from up there I could see into the cavities, in my case only 100mm wide. See the picture above for how effective the cavity wall insulation has been.
There is nothing in the cavity at all except cold, fast moving air. The lagging has only entered up to 250mm from the point it was sprayed in. Annoyingly, the holes are over 1,000mm apart.
So Mr Huhne and chums: If you insist on giving all the money to the insulation fitters, maybe you might want to check they are doing a good job.
Posted by Graham Hendra 22 October 2010 12:15:42 Categories: Graham's Gossip


By Bobby
22 October 2010 12:27:42
Agreed. Total waste of time and money. We had our walls filled and the house is cold all spring, summer and autumn. We have saved no money on the bills. It's long-johns and vests all summer here now.
By john
22 October 2010 12:26:42
Although done many years ago there is evidence that the moisture levels in the cavity are raised and while this has not penetrated the inner walls window frames are damp with wet rot resulting in places.
By Sue
22 October 2010 12:25:42
I have had cavity wall filling since Christmas with the wet weather it has penatrated from the outside to the inside of my house have had to remove wall paper as it has been soaking wet have had a humidifier running it is not getting any better it needs to be taken out wish I had never had it done
By brian
22 October 2010 12:24:42
I live in a detached bungalow in Ireland ,although only built in 1990s , its a really badly insulated house wit empty cavity and 2inch insulation backed plasterboard inside, I had my cavities pumped and it made no difference whatsoever, a thousand quid its cost me ,that's after the grant by the way,dont waste your money
By Craig
22 October 2010 12:23:42
My landlord has 50 years in the construction and repair industry. His primary job is high end products for industry, like 50 year warranted roof product, and damp course.

He will not have our cavities filled.mbecause as the original poster states, it does not spread. On top of that, it actually compacts in the injection area. And this creates a more dense (than planned) material for damp to bridge the gap.

Add to this that you cannot remove the stuff should you not like it.

They have sold a very rage amount of breathable coatings to councils who are using this on their outside walls, having had damp issues from cavity insulation.
By Brian
22 October 2010 12:22:42
I live on a 2nd floor flat (top floor).
We had our walls cavity insulated. The lower flats seem happy with the insulation, but my rooms fell just as cold as they ever did.
Is there anyone out there that checks for this?
By yvonne
22 October 2010 12:21:42
i had cavity wall insulation last year it took the guys 1/2 hour to do a detached house. i payed 250 to have it done and there is no difference to the heat. I want to get it checked as i believe the guys did not do the job propley
By David Stevens
22 October 2010 12:20:42
In my opinion cavity insulation is definitely something that I would recommend as it really helps reduce your bills and keeps heat in well.
By anon
22 October 2010 12:19:42
Cavity insulation is worth it - if it can be done properly. My parents, each winter, kept saying how cold their bedroom was each winter. Their bedroom has three outside walls with no cavity. It is a 100+ year old three-storey house. Two months ago I kinda went ballistic and stripped the entire room to the brick, created a cavity and put Kingspan insulation on the walls. I used foam insulation all along were the wall meets the ceiling, boarded and plastered, and fitted a new vent. Now they sleep with the bedroom door partially open and sometimes the window also and they say its too hot.

I have other walls which I cannot be bothered to knock down entirely and do the same to and so am seeking the best and cheapest way to pump insulation into the cavity. From what I have researched, sadly, it is not any cheaper doing a DIY as the equipment costs a lot.

Cavity wall insulation definitely makes a big difference. Obviously, make sure you have roof insulation also!
By Kenneth Duckett
22 October 2010 12:18:42
Come on Mr Hendra. It is not a waste of time. You seem to be referring to a number of poor installers - the people - not the worthiness of insulating a cavity. That's like saying you had a poor installer muck up your aircon install so all aircon everywhere is a waste of time. Or one kit is poor (no names) so all kit is a waste of time. That's a low IQ comment. Not what you would expect from a clever type like you.
Even mention of which government was in power is hardly relevant to whether it works or not. Well, not unless one is trying to provoke readers to waste their time trying to correct the main article.
The average cost to cavity insulate is under 200 for a semi. Not worth it? I am sure you can do the sums. The payback is under three years for most, which is definitely worth it, even where there are a few gaps.
And for those concerned about gaps....surely, a clever type like yourself would never pay up until after he had checked for hot spots with their thermometer -- ie areas on the outside wall that were still warm, where insulation was missing.
(I am not an insulation installer. Have had it done and regard it as NOT a waste of time/money. Also I do not read the Sun or Star.)
By David
22 October 2010 12:17:42
I agree with Graham it is a waste of time. I recently fitted some windows for my mother-in-law who had had her house injected some 25 years ago. In putting in lintels I had to remove bricks over the window and - guess what? - it was empty of insulation. What little was there blew in the wind like candy floss. In looking for a builder recently for my own self build project I went to look at one guy's work and there was no insulation in the cavities at all. When I inquired why he remarked it gets blown in at end of build. I was amazed that building control allowed it. To cap it all, this build was in an exposed area in Snowdonia. The cavity is there for a good reason a break between the two walls to prevent penetrating damp bridging across. It does not make sense to fill it .
By Ossie Wardell-Yerburgh
22 October 2010 12:16:42
Grahams Blog re wall insulation is well observed. However being as always in advance of my time, some 40 years ago I had the cavities of my 1950's house filled with blown polystyrene beads plus a bit of glue, which flowed very well and reduced my gas bill by 25% or more. This was done by Shell - don't think they or anyone else still does it? There were interesting problems, the first being that the electric ring main was run in the cavity as was presumably the norm at the time, so the "operator" hit it twice, it later overheated and caused a small very interesting fire! Fortunately self extinguishing in the end. Second the glue was not much good so a lot blew into the loft in a gale. I never paid them the second half of the bill, and they never pressed for it.
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