Venting (or not) and insulting 6:12 parallel chord truss roof
My first post a couple months ago was about an unvented cathedral roof with exterior insulation Ive been planning. Plans are changing because of the span. Well, my builder now wants to use parallel chord truss with a depth of 24″ to span the 41′ room. (6:12 pitch, single ridge in the center of roof. Standing seam metal roof. CZ 4a.) My questions: I was originally going to go unvented with another I-joist roof design, but should I now vent this parallel chord roof design? Im not sure how to insulate in the truss cavities now. Spray foam, fiberglass batts, other? It seems blown in products will sag and aren’t good for steep roofs like 6:12. How deep do I need to go? I think its obvious going the full 24″ depth in insulation would be overkill in CZ 4a. I can avoid thermal bridging if the insulation is deep enough to cover the top chord and possibly avoid the expensive exterior Hunter Panel foam board I was planning. I just need to know if this should be vented in some way, and what type and how deep the insulation should be. I dont want condensation issues down the road either. Thanks in advance.
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