Stud Wall + Insulation On Outbuilding

[hamd01]

We have an outbuilding at our new house which I'm looking to convert to a games/cinema room. It's around 5.5m x 4m. It was an old barn, but the current owners have had a new roof and plastered/whitewashed the walls. However, to mak it a proper usable living space its going to need properly insluating.

My plan is as follows, and id appreciate any advice if you guys thing this will be suitable. All the walls are outer walls, around 200 years old sand-stone.

Walls;
Batten the walls using 38 x 89 CLS Timber.
Fill spaces with Celotex GA4000 90mm for soundproofing and insulation
Rock Wool for any gaps around awkward shapes (eg cabling)
Polythene Vapour Barrier over the battons/Celotex
Debating non or insulated plasetrboard on top.

Floors
Similar approach as the walls, but the vapur barried first, then battens, then OSB boards with an insulation/carpet on top.

Be great to know if you guys think the above approach will offer decent insluation.

Thanks.

 

[oldbutnotdead]

For soundproofing you'll be better off with acoustic batts rather than Celotex. Thermally the acoustic stuff is less efficient than PIR BUT it is much easier to get soft batts airtight. Overboard the studwork with at least 25mm PIR, maybe 50 (do the heatloss sums, i CBA) then plasterboard. (PIR with foil taped joins is a pretty good VCL so thats one less thing to worry about).
Floor- no real need for acoustic there. If its flat you could just fit 100mm PIR and lay OSB as a floating floor. It might be more cost effective to use 150mm rockwool but then you have the added cost of timber.

 

[hamd01]

For soundproofing you'll be better off with acoustic batts rather than Celotex. Thermally the acoustic stuff is less efficient than PIR BUT it is much easier to get soft batts airtight. Overboard the studwork with at least 25mm PIR, maybe 50 (do the heatloss sums, i CBA) then plasterboard. (PIR with foil taped joins is a pretty good VCL so thats one less thing to worry about).
Floor- no real need for acoustic there. If its flat you could just fit 100mm PIR and lay OSB as a floating floor. It might be more cost effective to use 150mm rockwool but then you have the added cost of timber.

Cheers. to be honest with the floor, its as much about having space to thread a shed load of network and speaker cables that im wanting to batten it.

so you wouldnt use breathable polly sheeting at all?