I can't seem to get the same answer out of two peeps on this question. I want to reshingle my old roof which will turn out to be a cathedral ceiling. I'm worried about the shingles being able to breath after I spray foam between the rafters and want to know the right method to proceed with venting or not venting. I guess I should also mention, I plan to use 2lb closed cell foam and the roof sheathing is actually 1" boards, the shingles will be typical 30-40 asphalt shingles. Thanks for all comments.