Insulating a pebbledashed bay. Risk of interstitial condensation?

[Phillymclee]

So I’m currently renovation a 1930’s semi. The bay window was not insulated and constructed of lathe and lime plaster internally on 4x2 studs with timber boards wrapped in some sort of plastic and pebbledashed over externally. I wanted to improve the thermal insulation in the bay wall and also improve the acoustic performance due to the noisy road while I was at it. (I know the large window is the main cause of the acoustic transmission but we are having new windows installed and I wanted to try to improve all parts of the bay). So I stripped the plaster off and was planning to fill between the studs with rockwool rwa45 for acoustics and then overboard the studs with a PAR board for thermal insulation. This was before I actually done a lot more research and found out that lime plaster was far better than gypsum products for acoustics even with the rockwool batts. But hey ho we live and learn. So now the problem is that upon doing more research it appears I may now also have a problem with interstitial condensation as if I insulate the bay, even with a vapour barrier some vapour may still get through and then it has nowhere to go as it’s my understanding that pebbledash is not breathable. So I’m worried if I do this I could end up causing the studs to rot. Does anyone have a solution or advice for this situation? The only thing I could think of was replacing the pebbledashing for hung tiles which in my opinion would look better but I’m a bit reluctant to do that as the pebbledash appears to be performing well in terms of keeping the damp out currently, the studs are bone dry, and I feel that tiles would be an even bigger downgrade in terms of acoustics with all of the little gaps everywhere. Anyway anyone’s thoughts would be much appreciated. Thanks in advance. 

[Phillymclee]

Nobody? 😞