Zone 6 Insulating on the outside
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How does one finish the bottom edge of the exterior rigid insulation to prevent water seeping up? Is there a place to download typical wall sections of insulation applied on the outside including the drip edge, insect screen, insulation extending below grade, etc?
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Annie,
The GBA site has details for members. Here's what you are looking for:
https://www.greenbuildingadvisor.com/cad/detail/wall-section-cement-board-lap-siding-1-12-rigid-insulation
Concerning your questions:
1. If the bottom of the foam is above grade, the bottom of the foam is protected by wood trim, and an insect screen protects the bottom of the rainscreen gap.
2. If you are using rigid foam on the exterior of your concrete foundation, and if the plane of your foundation insulation is continuous with the plane of the rigid foam on the outside of your above-grade walls, you still need Z-flashing to separate the foundation foam from the above-grade-wall foam.
The wall section does NOT show anyway to protect the bottom of the rigid insulation. I am concerned about snow and thus moisture.
Annie,
Good point. It should. When I install rigid foam on the exterior of a building, I use a piece of wood trim of the same thickness as the rigid foam.
Another approach is the one used by Gary Bergeron: he protects the bottom of the foam with metal Z-flashing. You can see the flashing in this GBA video.
Thanks, Martin. How do you attach the wood trim as the insulation extends beyond the wood sill plate? metal z flashing works to. In that video it looks as if the sheathing stops on top of the sill plate so the insulation is right up against the foundation. ANOTHER question--is 1" insulation at the exterior as well as sheathing (my contractor prefers to add the sheathing) enough to insure no thermal bridging? I can get enough R with closed cell 2llb. between the studs.
THanks.
Annie,
The wood trim can be attached to the concrete foundation with Tapcons.
The minimum thickness of the foam depends on your climate. More information here: Calculating the Minimum Thickness of Rigid Foam Sheathing.