# Cavity block insulation



## Bostonian (5 Jan 2007)

My house is a cavity block (not cavity wall) house. A friend recently told me that insulating foam can be squirted in under high pressure to insulate the walls and there's a company that does this. Is this possible? It sounds a bit daft to me as the foam wouldn't be able to get into all the places you'd like it to, as opposed to how it would flow in a cavity wall.
Has anyone had this done? How did it work out? Was it expensive?


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## Sue Ellen (5 Jan 2007)

Hi,

Welcome to AAM.

I could be totally wrong but my understanding is that the type of cavity block wall that you describe is not suitable for this type of insulation despite what some salesmen might tell you. You might get some more advice from  Try giving them a call also.

These previous threads might give you some advice also.


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## sas (5 Jan 2007)

Hi,

This came up on a different board I regularly read and the answer there was no better.

There are a handful of companies out their claiming they can pump cavity block walls but it's highly likely the result would be poor.

What may be an option (albeit a damn expensive one if its in the same price range as other products I've seen) is external insulation.

Last november Weber achieved an IAB cert for their external insulating system. [broken link removed]=

External insulation is apparently the way to go if you can. There was an article in the examiner last monday about Irelands first passive house and it is insulated externally. The insulation system (Dryvit) they used was from www.greenspan.ie. It doesn't have an IAB cert however. It costs in the region of 100€ per sq. metre (+ VAT) installed and rendered so it ain't cheap.


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## Bostonian (5 Jan 2007)

Thanks sueellen and sas. I agree with you both that it couldn't possibly reach all the places it should but I thought perhaps someone out there knew something I didn't. And, of course, there's no way of checking! Thanks also for the links. I had a quick peep and there's plenty there for me to check out.


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## Jess7 (2 Feb 2008)

Hi I'm new to the whole forum world and came upon this site when I was looking for information about Cavity wall insulation. 

My house is built of cavity blocks and I have been told by two firms that it is possible to insulate cavity block brick wall.

I haven't had a chance to ring SEI yet but on their website they say "it is not possible to fill the cavity in a wall constructed simply of 9 inch hollow blocks"

Has any one had any experice of the foam fill treatment on offer or got any advice.  I haven't got a huge budget for this and the price offered by one company seems reasonable but obviously I don't want to go ahead if it's a waste money.  Any help gratefully received.


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## sydthebeat (2 Feb 2008)

The only way you can ensure a cavity block wall is totally sealed with pumped-in insulation is to drill into both chambers of ever block... thats not practical.


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## Jess7 (7 Feb 2008)

Thanks for that sydthebeat ... Just to post this on the site, perhaps to help someone else, I spoke to an Engineer, who is affiliated to SEI' who basically told me that to try and insulate cavity block wall in this way is a complete waste of money.  NSAI reiterated that this was indeed sound advise!


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## Mr Sparkle (7 Feb 2008)

It's advisable to not insulate in this way, the main risk being interstitial condensation, i.e. condensation within the block, which cannot therefore evaporate. This will eventually lead to a deterioration of the building envelope. Always better to insulate internally (drylining) or externally (insulated render system), or ideally both.


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## beaumont-08 (24 Apr 2009)

Purchased a house last year. built early 60's, cavity block, and some 4"x9"x18" block on flat around windows. Very cold over the winter.
Decided to insulate the house with 50mm drylining on all external walls. 
Small bedroom, 2 external walls had non insulated drylining already, so builder advised removing the plasterboard... 
the 20mm render came with it... in 2 and 3 foot sections... 
exposing all the blockwork, which was dark grey and wet...

Not something you want to see happen to you house... when you have no idea of the building trade...

Engineer called to the house and discovered rows of 'patched' holes all around the gable end of the house. Someone tried to insulate cavity blocks, drilling each one, and pumping them. But the blocks were never sealed.

We now face having to strip and re-rended the whole house.

My advice... don't even think about. It will destroy you house.


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