Insulating a Standing-Seam Metal Roof on a Deck-Style House
Hi All —
Getting ready to do a total reroof. Deck House-type construction. I’ve seen a number of postings that address some of our issues, but nothing specifically.
Built in 1963 outside of Boston. Not by Deck, and not by TechBuilt, but has similar characteristics. Roof is very much like a Deck.
Ceiling is 3×8 T&G Fir. This is also the roof deck, originally covered with tar paper and shingles. Was retrofit poorly around 1990 with 2×6 sleepers, rigid foam panels, plywood sheathing, and architectural asphalt shingles.
We have a bad leak that needs to be fixed. Seems to be affecting a number of areas around skylights.
Rip off everything down to deck. Recover w/vapor barrier, 2 layers of overlapping and taped polyiso panels like Hunter or RMax, followed by 5/8″ ply or OSB glued and screwed through panels, ice and water shield, and architectural asphalt shingles.
Same as above, but forego sheathing and cover w/standing seam roof.
Rip off existing sheathing. Remove & discard existing rigid foam, retain sleepers and fill cavities with spray foam, ice and water shield, and standing seam roof. In this scenario, we would also look for spray foam to act as a vapor barrier, not sure open foam can do that.
I know the standing seam can go directly on the polyiso panels without the need for sheathing. But can we substitute spray foam for the panels?
I’ve seen postings here about the pros & cons of spray foam, and not sure which, if either, is appropriate for this install. Open Cell is about the same price as the polyiso panels, but it is a big labor saver. It seems to be a fire hazard, and attracts water like a sponge
I’ve also read here about combining rock wool with spray foam.
We’re trying to find a solution that’s cost effective and can provide good R-value…would Closed Cell work???
Looking forward to hearing the group’s ideas…thanks!
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