Planning to build a timber frame garden office
The idea is to use a "warm roof" and insulate the walls with rigid insulation, Kingspan or Celotex. The question is how deep should that be? Some advice talks about 100mm in the walls and on the roof with an extra 50-75mm over the frame before the plasterboard. That would eat into my head room and room space, so ideally I want a max of 90/100mm in between 4x2s in the walls and even less for the roof if I can get away with it to gain a bit more head room. Will I be too cold in winter?