Superinsulating the House

The foundation was insulated with 4" of XPS (extruded polystyrene.) Expanded polystyrene (EXP) was not used because it absorbs water, which is problematic in an exterior environment.

The top edge of the polystyrene was beveled away from the house to shed water. Metal lathe was bent to shape and nailed to the sill plate and spiked to the insulation.

The foundation walls were dry-stacked concrete block with a fiberglass/cement parge coat. The blocks were then filled with grout.

Placing the insulation on the exterior of the walls brings the mass of the walls inside the thermal envelope. Exterior insulation also helps prevents condensation inside the house, which could lead to mold problems.

Stucco was applied to the metal lathe to protect the insulation from sunlight, insects, and physical damage.

Prior to backfilling, 2" of XPS was laid down as tundra insulation.

In the center is Sunny. The tops of the two smaller ferrocement filters in the crawl space are visible in the foreground.

The interior set of studs of the double wall construction is visible.

Sunny is standing to the right of a big pile of insulation still wrapped in plastic.

The exterior set of studs of the double wall construction is visible on the first floor of the two-story part of the house. The walls are 12" apart, and when filled with fiberglass insulation, gives an R value of about R-40.

The double wall construction on the second floor is visible here.

The house was not sited to face the road. To maximize solar access, it was oriented to face due south.

The original siting was done by Boomer on the autumnal equinox on September 22, 1989. He set up stakes that lined up directly with the setting sun, which sets due west on the equinox.

This photo was also taken on the autumnal equinox. The built-up posts in the center of the house are pointing due west, directly at the setting sun.