The insulation followed the same path as the air barrier to wrap all six sides of the cube. Starting at the basement, the existing slab floor was covered with 2 in. of XPS. The existing basement walls were covered on the inside with 4 in. of closed-cell spray foam. The exposed sills at the basement were sprayed from the inside as well. Then the exterior above-grade walls were filled with cellulose, using the traditional method of making small holes in the exterior sheathing. The two 2-in. layers of polyisocyanurate were installed over the whole exterior wall.

The roof vents were sealed, and the wall-roof intersections were lined from the inside with building paper to provide a temporary dam for the application of spray foam from the interior. Two additional 2-in. layers of polyisocyanurate were then installed on top of the roof deck.