Propanel siding over 2″ rigid continuous insulation
sheropod2
| Posted in Energy Efficiency and Durability on
My friend is building a 2×6 frame house, R-19 with 2″ of continuous insulation over it. She will be using metal propanel for the exterior cladding of walls. Interior will an be air-tight drywall installation.
The house is in northern New Mexico, climate zone 5B, elevation of 7,000 feet.
Two questions: will there be a problem attaching the siding through 2″ of foam, and will a drainage plane or rain shield be needed? One more question – I assume a WRB should also be used over the continuous EPS, but what permeability should it be?
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Replies
Melissa,
It would be a lot easier to strap the foam and fasten the Pro-panel to the strapping, rather than through the foam into the sheathing. That also gives you a rain-screen gap.
The builder wanted to attach 2x2s to the studs, which would give him something to screw to, and that would provide a gap for a rain screen, but the owner will no longer have functional continuous insulation. It sounds like you are saying to strap over the foam, screwing into the studs. Would those straps have to go over the studs or can they be attached to the sheathing through the foam? PS - Thanks for your help - I'm studying building science and have only worked on SIPs houses until now. I'm so grateful for the help I get from experienced people!
Melissa,
Any time exterior foam exceeds a certain depth (typically 1"), strapping (usually 1"x3" or 1" x4") gets screwed through the foam into the studs to provide a nailing base for the cladding. The length of the fasteners depends on the spacing, and the depth of the foam. You can find details for this in a number of guides. here is a link to one: https://www.victoria.ca/assets/Departments/Planning~Development/Permits~Inspections/Example~Plans/Illustrated-Guide-R22-Effective-Walls-In-Wood-Frame-Construction.pdf
The building code clearly requires that strapping or furring for claddings must be attached to structural framing.
Peter
Ours doesn't.
I live in the sticks, so this long distance help is wonderful! Thanks!