I am going to build a new outbuilding to house my woodworking shop. It is a historically designated property, so I am restricted by the external dimensions. It is an elongated building and I don’t want to take too much of the depth as it will become difficult to furnish practically. I have decided on 120 mm studs in the walls and 220 in the roof. I have two questions: 1. Should I use 120 mm studs, or would 70 mm with a horizontal 45 mm be better from an insulation perspective? Then the plastic or vapor barrier can be within the wall? 2. Will 220 mm studs in the roof work with a spacing of 120 cm when the span is about 3.55 m? It will have tongue and groove boards and felt on the roof, so it is a light construction. Regards
Don't have an answer to your ceiling question, but having only 70 mm from the outside to the vapor barrier sounds a bit low. 45 + 70 mm is, as you say, better from an insulation standpoint, but place the vapor barrier on the innermost side.