Battening wall for insulating internal leaf of external wall

[nishnish]

Hi,
Plasterboard with insulation attached is pretty expensive compared to getting plain PB and PIR boards.
Is it better/easier to have the air gap next to the wall or next to the PB?
Celotex show using their GA4000 PIR boards, putting them against the wall and putting the battens over, leaving the air gap next to the PB.
Supppose, it makes it easier to run cables etc without damaging insulation?
However, when contacted, Celotex didn't seem to quibble with the idea of battening the wall first and having the air gap next to the wall.
I was wondering what someone with experience of any/either thinks about the relative merits of air gap positioning?
How do you attach something heavy like a radiator to a wall insulated with relatively thick ~50mm PIR? Wouldn't the required strength fixing tend to crush the PB/PIR?
Thanks.

 

[joinerjohn]

When battening a wall to insulate the wall, you have to plan well ahead. If there are radiators going on to that wall, you can work out where the brackets are going and make sure there are battens behind the plasterboard at those points. You then have something to fix the brackets to.
You could of course fix thicker battens only at these points (same thickness as insulation + airgap, so the brackets fix directly to them through the plasterboard and so stop any crushing effect.

 

[nishnish]

Thanks for that.
Thought as much. No solution, but careful measuring, eh?

If the extra battens are air gap + PIR thick, as you suggest, there's no issue with crushing the PB?

Anyone got any views/experience on relative advantages/disadvantages of having the air gap next to the wall vs. next to the PB?
TIA.

 

[crossercuss]

i was thinking of doing a similar thing to some of my walls and i did think about plywood sheets under the plasterboard so things can be fixed to the wall much easier.. not sure if it would cause problems or not though..

 

[nishnish]

i was thinking of doing a similar thing to some of my walls and i did think about plywood sheets under the plasterboard so things can be fixed to the wall much easier.. not sure if it would cause problems or not though..

I'm guessing you mean that you'd have the air gap just behind the PB and fix the plywood in the air gap?

If the air gap was against the wall then the plywood would be behind the 50mm PIR and still run the risk of crushing the insulation? It'd be little better than fixing straight through into the wall? Except you could avoid cold(er) bridging I suppose?

 

[ajrobb]

http://www.celotex.co.uk/Applications/Wall-Insulation/Solid-masonry-walls-Internal

They have PDF manuals you might find informative.

There are alternatives to PIR. You could use mineral wool:

http://www.proctorgroup.com/Products/CondensationControl/ReflectathermFoil.aspx