Injection of foam into cavity walls

2011

I live in a detached house. Three of the external walls are cavity block. A well known company carried out a quick survey and recommended filling the cavities of the blocks with a foam insulation. I am wondering if this is going to make much difference as there will be multiple cold bridges. What are peoples views on this? Thanks.

jack of all

I considered it for my own house years ago but decided against it in the end. A friend of mine got it done and was pleased with the improved thermal comfort initially, but after a year or two he started to see problems with mould in certain rooms and at known cold bridge areas. In a clean cavity, with properly fitted dpcs and trays etc it should theoretically be fine but if you have lots of mortar snots, badly fitted trays etc I imagine this can be problematic. Some new builds are going for a 200mm cavity now, pumped after construction, but equally how can you be sure that the beads or foam are reaching all parts of the wall cavity?

dathi

if your walls are made with these

https://www.goodwins.ie/products/Cavity-Concrete-Block-215mm-9-7.5N-Hollow.html

then do not fill with either foam or beads as neither have certification to be used in these type of blocks. the large amount of thermal bridging across the webs of the blocks can cause mould issue's . if on the other hand your walls are made of two 100mm concrete blocks with a cavity between them , then this cavity can be filled with beads .

Gusser09

Look at external wall insulation with proper vents fitted.

loyatemu

it's a terrible solution, as you point out there will be so many cold bridges how could it possibly work well.

I don't believe it's recommended by the SEAI or any equivalent body elsewhere; the only people who recommend it are the companies selling it.

2011

Thanks for the feedback, you have confirmed what I was thinking.

Regarding external insulation, this is simply unaffordable and it would be difficult to implement on my home for a number of reasons.