Cavity wall insulation

jonna

Distinguished Member
I've had a phone call from Energy Savings Trust, informing me that i can get my cavity wall insulated, from a local business under a government backed scheme, for £75.

I agreed to a phone call, to arrange a survey, but since then i have been told by two people that it could lead to penetrating damp problems.

Has anyone any experience with cavity wall insulation and can different types/quality of brick affect the problem?
 

Mr Incredible

Distinguished Member
I had cavity wall insulation injected into the house over 20 years ago. It's a 1960 brick bungalow and I haven't had one problem with damp. It was installed by Corning and carries a 100 year guarantee.
 

AndyCob

Well-known Member
The cavity in a cavity wall is there amongst other things to prevent damp crossing. In theory if applied properly the modern cavity wall insulation is sprayed in to only stick to one side and still leave a gap to prevent moisture soaking across it. The older style which filled the gap completely or the newer if applied badly so it fills or contacts both sides can lead to damp issues by providing a means for water to soak acroos. At least that's my understanding, of course things need to be damp enough that the inside of the cavity is wet for it to matter but it's a case of pay your money take your chance, it's not likely to cause a problem but it can happen.
 

baldrick

Novice Member
I know that spray foam insulation doubles up as a vapour barrier, so surely if they use a similar compound in the cavity there would be no risk of moisture transfer?
 

Andyh4324

Well-known Member
I was always told the polystyrene beads is the best to have as it doesn't leave pockets around the wall ties where the fibre-glass can get caught. Also means less holes in the wall as far as I know as they drill at the top and just fill the cavity up.
 

jonna

Distinguished Member
Thanks all,sorry for the delay in replying, i've been fitting my new kitchen. Still unsure as what to do as i think the bricks used to build our house seem prone to absorb water easily because in winter the brick face blows off the odd brick after a frosty spell.
 

jenam93

Well-known Member
When you have the survey done they should drill holes into the cavity and check out the condition inside.

We had ours looked at but there were a number of wall ties completely caked in mortar and the surveyor said if we went ahead with the CWI we would end up with damp problems that would be nigh on impossible to get rid of.

There is no doubt that CWI works really well for most people, but there are always going to be exceptions such as ours.

You just need an honest surveyor checking out the cavity for you!
 

Flipper

Novice Member
I have considered cavity wall insulation a few times for my house, but have always decided against it. My father has worked on several buildings where the insulation had to be removed due to damp so he always advised me not to have it done. Google will soon show you some examples of people having it removed :eek:

It's all very well having a nice long guarantee but if it goes wrong it will be a lot harder to remove that it was to put in.

The other thing that put me off was the number of holes that had to be drilled for the filling process. It's not just a couple of holes. Also the holes were not quite small enough to be drilled in just the mortar, they would have taken off the corners of the surrounding bricks as well.
 

figoagogo

Distinguished Member
We have just had a free survey (with the hope of getting free installation from BG). However, it seems that one set off walls would have needed the insulation installing from the inside, which would require holes in walls and tiles!!! Put me off.
 

p9ul

Distinguished Member
Had cavity wall insulation done about 5 years ago and had no problems with damp. The stuff they put in was like cotton wool.

As flipper says, the nozzle they use is slightly larger than a mortar joint so it does take the edge off bricks - but how noticable that will be will depend on your bricks - we have a red "rough" brick and you can't tell any difference really, although part of our house is rendered and you can tell there because the render they used is a slightly different colour.

Not entirely sure why they'd have to insulated from the inside - did they say why?
 

RMCF

Distinguished Member
You should get it done.

You are lucky you are on the mainland and can get work done for such small money.

Here in NI we get none of these deals. And you also get insulation at giveaway prices in B&Q, Homebase etc, we have to pay big money for it as we don't get subsidised materials or labour.
 

bobflunkit

Well-known Member
We used to have damp in a flat we rented and then the landlord had cavity walls insulated. Problem solved,never had damp again.
 

Berties

Banned
And you also get insulation at giveaway prices in B&Q,

yeah did loft insulation, each roll 20cm thick x 4-5m length was only £3! (and the full width rolls, 3 wide not the single ones)
 

danmc_82

Suspended
I wish I could insulate my house so easily. I have a solid brick house so I have to insulate the inside of my rooms. Not the best job to do :(
 

p9ul

Distinguished Member
I wish I could insulate my house so easily. I have a solid brick house so I have to insulate the inside of my rooms. Not the best job to do :(

You can always insulate the outside and then render over the top of it - means you lose the appearance of the brickwork though...
 

eob

Well-known Member
Another advocate of CWI here.
I too was worried about damp crossover but took the risk as our house is semi sheltered anyway.
We got the fibre type insulation but the guy assured me that it is treated with an oily substance so that any moisture will run down.
Anyway, the house is much cosier now and the draughts under the skirting (we have wooden floors throughout) have been erradicated. Did the loft insulation at the same time too and have noticed a massive drop in heating bills.
 

danmc_82

Suspended
You can always insulate the outside and then render over the top of it - means you lose the appearance of the brickwork though...

I know plus alot more expensive.

Dont like rendered houses, suppose I could go for the pebble dash or stone cladding look :D
 

jonna

Distinguished Member
Bumping my old thread because I've had a local firm trying to persuade me to have cavity wall insulation. I'm still concerned about penetrating damp once the cavity is filled.
I'm having new double glazed windows fitted next week and this could be another way of keeping the house warmer in winter.
I need convincing either way.
 

danmc_82

Suspended
If I could have it, I would.
 

Fatti

Novice Member
We've had cavity wall insulation for 4+ years now and not a single sign of damp. That coupled with new windows and loft insulation, the house is like a sauna in winter :)
 

jonna

Distinguished Member
Think I might cancel the survey, too many issues on the internet. I've just read this :- Ok, lets put this into perspective, there have been thousands of cavity built houses within the UK that have been insulated and a good majority of these don’t currently have nor will ever have a problem with damp. But there are a great number that have and no doubt more will be affected in the years to come!

Increased rainfall in past years has resulted in a noticeable increase in damp problems affecting conventional cavity-constructed housing, due to moisture penetrating / bridging the cavities and in particular on the weather prevailing elevations and this isn’t a problem relating to current rainfall, but a gradual build of damp over many years.

Rainwater driving into the masonry of a building can penetrate the outer leaf brickwork leading to the wetting of the insulation materials, increased damp penetration and a reduced thermal performance of the material. Poor construction methods, mortar and perp joints, debris within the cavities, dirty wall ties and poor installation procedures by installers all contribute to the overall problem, which generally will result in the need to remove the insulation, which is not only expensive, but will almost certainly cosmetically scar the building when finished. Unfortunately it doesn’t come out through the same hole through which it went in!
 

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