Insulating un-even wall

[jayc89]

I'm trying to insulate an internal wall. 50mm PIR adhered directly to it, followed by and airtight membrane (I know the PIR, taped should also provide this - but belt and braces...) then battens through to act as mechanical fixings and a service void.

 

The wall is approx 20mm out of plumb at its worse and I didn't want to leave any void/air gaps between the wall and the insulation to avoid the risk of cold air from outside ratting around behind the insulation.

 

There is no option to tackle this work from the exterior, unfortunately. 

 

Short of dubbing the wall to level it off, what would be the best course of action?

[Redbeard]

Not sure you can stop short of dubbing out. is the 20mm 'out' random or defined? Could you accommodate it with a 10mm toothed coat on the wall and (with possibly some tacky PVA to stop 'slippage') 10mm on the board? Use a nice soft lime mix.

[Radian]

51 minutes ago, jayc89 said:

50mm PIR adhered directly to it

Using plenty of low expansion foam adhesive, create horizontal cells to limit convection - and treat the pockets as a feature, not a bug?

[jayc89]

20 minutes ago, Redbeard said:

Not sure you can stop short of dubbing out. is the 20mm 'out' random or defined? Could you accommodate it with a 10mm toothed coat on the wall and (with possibly some tacky PVA to stop 'slippage') 10mm on the board? Use a nice soft lime mix.

 

It's pretty random, I guess the apprentice got the job of laying the internal bricks back in the day  I do have a couple of backs of lime kicking around that I could use, but I can see it turning into a pain to get level given how random the gaps are.

 

11 minutes ago, Radian said:

Using plenty of low expansion foam adhesive, create horizontal cells to limit convection - and treat the pockets as a feature, not a bug?

 

A foam adhesive opposed to an expanding foam? Something like Pink Grip foam, Insta Stick or Illbruck PU010?

[Radian]

1 hour ago, jayc89 said:

A foam adhesive opposed to an expanding foam? Something like Pink Grip foam, Insta Stick or Illbruck PU010?

Yes,

 

[jayc89]

10 hours ago, Radian said:

Yes,

 

 

Are any more appropriate for a more airtight seal than others? I know Illbruck to an airtight foam, but I don't think it's meant to be used as an adhesive.

 

Would a membrane behind the insulation, perhaps double sided taped to the wall (following its undulations), to try prevent any wind getting to the insulation at all be overkill?

[Radian]

1 hour ago, jayc89 said:

Would a membrane behind the insulation, perhaps double sided taped to the wall (following its undulations), to try prevent any wind getting to the insulation at all be overkill?

That'd be almost impossible to get a secure bond to. I think you're overthinking this. If you go over the wall with the low expanding adhesive foam wherever you see any dodgy bits at the same time you matrix-up the back of the insulation you're certainly not going to get a howling gale going on behind the sheets. Convection is stymied by continuous horizontal lines of adhesive. The airtightness of just about any type of foam would prevent mass airflow. But maybe someone else here has experience of using FM330 to bond rigid PIR?