Injecting insulation behind the dot and dab cosyboard

john oneil

Hi All.

I am wondering if anyone is familiar with injecting air tightness insulation foam behind the 38mm cosy board which was originally fixed onto the block wall using dot and dab. The wall wasn’t sealed prior to the fixing the cost board and generated a cold airflow behind the cosyboard.

I got airtightiness test with thermal camera done and it showed the cold air coming from the skirtings

my house is losing heat quickly even though I have beeds in 100mm cavity.

I was told by a insulation contractor that he can inject a liquid into cosyboard by drilling 10mm holes through cosyboard and it will seal the complete wall

he also said he can inject it into the suspended plasterboard (12mm) ceiling which has a void of 100mm to underside of the RC concrete first floor slab

i would welcome any advice / recommendations

10-10-20

Hi! When you say "the wall wasn’t sealed prior to the fixing the cost board and generated a cold airflow behind the cosyboard", was the cozyboard fitted to bare block-work or a sand/cement skim on the blocks? What age is the build?

What's going to stop the foam from popping the dabs and delaminating the cozyboard from the wall? I'd guess that the injectable foam isn't rated or tested for this option.

john oneil

Hi there.

thanks for your response.

the cosyboard insulation board was dot and dab straight onto the bare block work. No scratch course was applied.

I understand the foam is not an expandable product so should not put pressure on the board.

welcome your insights.

10-10-20

What area of wall needs to be treated? Is it whole house or a partial install? Was a foam product mentioned by the installer (such as BASF Walltite)? Did they mention requiring an indemnity statement at all?

My understanding (although limited) is that expanding insulating foams have to exert pressure to be able to expand within the cavity anyway. That's the main mode of deployment and that has caused some (very limited) amount of issues with weakened double-leaf walls where it has pushed the leafs apart. Let's see if other opinions can add to the discussion here.

10-10-20

@DOCARCH - might be better having this under Construction and Planning...?

KungPao

Wouldn't it be easier to whip off the skirting and seal up the bottom of the boards? Cut the boards to under skirting level, some skim coat over the visible blockwork, when that's set put some airtight tape from under the board down to floor, then some ex foam into the void, then skirting back on after trimming the cured foam.

A little bit a cool air trapped behind the insulated wall board...is it that big of a deal? (assuming it's now sealed at the perimeters and around any sockets)

GreeBo

https://www.boards.ie/discussion/comment/121737292#Comment_121737292

Thats what I did, though I used foam as its what I had to hand.

Cut it back and refitted skirting.

However, depending on how bad it is, you will still have problems around sockets and switches unless you also do the sides and top of the walls.

/edit to add that I did also use expanding foam once before in the middle of a plasterboard wall (where it had come away from the dabs and the foam pushed the rest of the dabs from the wall and left a bow that I had to cut out and replace!)