Insulation

[Chillipalms]

I am currently in the process of building myself a man cave it's 4.8 x 3.6 x 2.4
I have built it with 4x2 walls then 12mm ply, breathable membrane ,25 mm batten, and eventually featheredge. My question is what's the best insulation, mineral wool or celotex and what thickness is the best if I use rockwool can I full fill or if I use pir boards will 60-70mm suffice???
Oh and inside shall be plastered
Cost is also an issue need the benefits of both thermal value vs cost
Many thanks

 

[Chillipalms]

Also I am going to screw plasterboards to the studs should I use vapour barrier plasterboards thanks again

 

[noseall]

Celotex every time, because not only is it superior regards insulation properties, it also benefits the user long term with the foil sandwich vapour barrier.

Additional vapour barrier on the warm side will do no harm, neither will foil taping the the insulation joints once they have been fitted betwixt studs.

Do it once and do it right.

 

[Chillipalms]

Brilliant cheers for that tried searching the Internet and had to much conflicting advice