Vapor Permeable Exterior Insulation
Matt Melton| Posted inGreen Products and Materialson
I can’t seem to find any Rockwool or Gutex products for my exterior insulation. We already have a vapor barrier on the interior side of the wall, so, I’ll need a permeable option on the outside…at least I assume I do. Any ideas? It’ll be corrugated metal siding. Could I compress 2×4 Rockwool batt? I could skip the exterior insulation, but I’d rather not.
It’s been a while since I’ve paid attention to what the current practices are.
Thanks!
Matt
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Replies
The right thickness of unfaced EPS will work well.
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Matt,
Make sure to vent the bottom of your corrugated metal cladding.
My go to budget permeable foam is fiber faced roofing polyiso. This comes with a fiberglass facer, depending on the manufacturer and thickness, it tends to be above 1 Perm.
The facer on this foam absorbs water, so your WRB needs to go over the foam. If this is not a type of install your contractor is comfortable with, go for unfaced EPS/GPS or low GWP XPS foam as Jon R suggests.