Outside insulation is an efficient way to keep heat in. The devil is in the details like this one
Old-fashioned walls had siding over house wrap, over wall sheathing, which worked great until exterior foundation foam became a thing.
R-15 foundation insulation is required in cold climates, like Minneapolis, and the best way to do it is to the outside. This means about 3 inches of insulation.
You could add a wide flashing to span the foam, but OA Design Build has another way to do it.
Step by step:
- They begin with waterproofing on the outside of the foundation all the way to the capillary break on top.
- Next comes the insulation.
- Cantilevering the framing over the edge of the foundation about ½ in., leaves just enough space above for ZIP R-12 sheathing to flush out with the face of the foam.
- The joint is then taped against air leaks.
- The local building department requires a plastic slip sheet below grade, to protect against frost heave.
- They also require a protective cover, like coil stock, above grade to protect the foundation insulation.
Now they can add a rain screen and siding for a neat transition that keeps the heat where it belongs.
—Michael Anschel owns Otogawa-Anschel Design+Build in Minneapolis, Minnesota