Naio wrote:
Am I correct in thinking that there needs to be an airspace between the roof and whatever is under it, and around the edges, and then a semiwaterproof layer (because moisture will condense in the airspace), and then insulation? So, for example, would it be appropriate to attach closed cell foam to the roof ribs? (What do you call them? Not rafters...) And maybe cover with fabric?
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Closed cell foam boards are good but fitting and gluing those tight enough into all those turns and curves would be a helluva job and probably use a ton of glue,
remember you should make this air tight so no warm air ever gets onto your cold metal roof,,it would sweat make condensation,,fabric is not air tight unless it's some kind of plastic,
Theres no need for airspace unless you could make it airtight from inside..