Insulation for concrete cavity block walls

Picaresque

Hi,
I am looking at insulating my living room.
I have two cavity block walls and I am wondering if I could use 42.5mm wall dry-lining insulation board like the Kingspan K16 one.
Can I glue the board directly on the wall without leaving space between?

Would it create moisture between the wall and the insulation if I don't leave any space?
Thanks!

10-10-20

https://www.boards.ie/discussion/2058349801/insulation-for-concrete-cavity-block-walls

Hi! Provided that they are installed as per the manufacturer's instructions, composite insulated plasterboard should contain a vapour control layer which will act to prevent moisture from reaching the wall in any great volume and allow the wall to naturally breathe and permeate any built-up moisture. You can glue the board to the wall using a suitable plasterboard adhesive foam, but you also need to install mushroom fixings to physically secure it to the wall. You can achieve gaps of around 5mm to 10mm between the wall and insulation using this method.

Picaresque

Perfect, thanks!

In fact, they are hollow blocks, not sure if it makes a difference.
Good to know that I won't need to install battens first.
I read that the gap was supposed to be at least 25mm, would 10mm be enough?

10-10-20

https://www.boards.ie/discussion/comment/122087051#Comment_122087051

25mm sounds like the dots and dabs method of adhering insulated plasterboard. That creates a void which allows convection and what's called a thermal loop where heat can move. For that reason adhesive plasterboard foam is better as that thermal loop can be prevented.

Have a look at some YouTube videos for examples on how to apply boards using the foam.

https://trade.evo-stik.ie/sites/trade_evostik_ie/files/2021-07/30610927-plasterboard-adhesive-foam-gun-grade-tds.pdf

And don't forget the mechanical mushroom fixings which will also allow you to pull the board in even more.

Picaresque

Ok thanks
It seems that there is not a lot of choice for insulated plasterboards for hollow blocks, the only one I can find is this one:
https://tjomahony.ie/50-5mm-x-2-438m-x-1-2m-insulated-pir-plasterboard-8-x4-t-liner-128020.html

I would go for 50.5mm for the walls and 37.5mm around the windows as 50.5mm would be difficult.

I am not sure there is another brand I could use?

mp31

https://www.boards.ie/discussion/comment/122107879#Comment_122107879

Do hollow block (which I presume include cavity block as used by a lot of houses in Ireland) require different insulated plasterboard for IWI?

Picaresque

So back on this.
I spoke to a builder, he told me that I should not bother and I should just take PIR Insulation Board and mechanically fixed them onto the wall, without batten, dab and dob and without any space.
Also, If I do that, I dont need to strip the painted wall paper off.

So I am not sure now.
Any idea?

10-10-20

https://www.boards.ie/discussion/comment/122360557#Comment_122360557

Standard PIR boards will be foil-faced and will need to be mechanically fixed or fixed between battens and then overlapped with plasterboard. They won't adhere to dot and dab due to the foil. Example here:

https://brooksonline.ie/mannok-2400mmx1200mm-therm-floor-insulation-40mm-um6323

But by the nature of dot-and-dab you're always left with a small gap.

Did he mean insulated plasterboard by any chance?

https://brooksonline.ie/kingspan-k16-2436mm-x-1196mm-insulated-plasterboard-37-5mm-uk6186