Our previous post introduced a Passive House project that we designed and carried out in Maine. This post will describe the building materials and methods used.
We didn't need or want a basement, so one of the first decisions was to sit the house on a slab on grade. Our local builder, Jesper Kruse, had experience with an approach called shallow frost-protected foundations, so he ordered a system of custom molded foam blocks that fit together like Legos. The foam provides an insulation value of r-50 beneath the slab, which is 5 or 10 times more insulation than normally installed beneath slabs. Without a well insulated slab, the house would not perform well, nor would it meet Passive House standards. And since the concrete also serves as the finished floor material for the first floor, it was important to make it comfortable under foot. A heavy duty vapor barrier was placed on the foam prior to pouring the concrete.