I've just torn down and repaired a room due to water damage. Right now, it's open to the attic and I have the opportunity, for this particular room, to build in air gaps against the sheathing in the ceiling before I put up insulation and a new ceiling. The house does NOT have air gaps anywhere else and it is a nice attic without growth. The house is a log house from 1906; adding air gaps when I have the chance seems like it can only be better, right? It's not like it could get worse from it?
It's not possible to give a good answer without knowing more about what it looks like beside this room.
When the house was built, it was likely with an underroof of spån/pert, then no air gap is needed, since it is not tight. If it has later been replaced with tongue and groove with tar paper, you should definitely have an air gap. The advice given is based on quite a few guesses about your roof. What do you have on the roof?
It is standing seam metal. We have just got a new one as the previous one leaked in various places, hence the water damage. Now they have put felt under the metal, whereas the metal previously lay directly on the boards. Will there be a difference in the climate with the new roof? It was standing seam before as well.D Daniel 109 said: