Notes from the Underground

This sustainable house in New Canaan is not exactly mid-century modern but it's fascinating nonetheless. It seems though that sustainability isn't selling any better than regular old energy-wasting McMansions: A Raveis broker sent me a listing and two pages of details last April, when it was on the market for $2,395,000, and yesterday another Raveis broker sent me the listing again, priced to sell at $1,795,000.

The house was built 20 years ago and was designed by Donald Watson (here's his CV, which shows some interesting projects in urban planning and open space preservation), but I have no idea if it works as advertised. Here's what a Raveis broker sent me:

This residence was designed to provide a high level of thermal comfort, natural
lighting, and a sense of quiet and integration with the surrounding natural landscape. The home is nestled into a south-sloping site amidst gardened terraces and is built above-ground. Yet it is considered an under-ground house because its east, west and north sides fit into the hillside, and its roof is covered with a two feet of earth and grass. …

Many advanced building features are demonstrated in the house including earth-sheltered and passive solar design, light reflectors, photovoltaic electric auxiliary, batch solar water heater, thermal storage fireplace and an air-to-air
exchanger.

The house was built in 1986-87 to the owners specifications. The residence was
designed to be “self-heating” during the cold winter months. After the first year of living in the house, it was determined that the prior February the house maintained an average temperature of 69F inside during a winter period when the outside average temperature was below freezing. …

Also significant is the natural lighting. The ambient level in the major habitable
areas in the house is above 80F in sunny to partly sunny conditions throughout the year.

Special features that save energy and contribute to environmental quality: The entry serves as a combined air-lock and a greenhouse. In the greenhouse is a pebble bed in direct contact with the ground where a drip watering system is installed for easy moisture management. A fountain in the “garden” provides splashing water noise throughout the house.

Skylights at the north side of the house admit daylight two stories down, and the exterior light-shelves at the south windows shade the windows from summer sun and bounce sunlight deep into the interior which provides usable balanced daylight throughout the year. …

The house is a concrete shell covered with earth. The underground walls are waterproofed with Bentonite, a clay based product that swells in moisture and becomes impenetrable to water. The roofs are waterproofed with heat sealed EPDM rubber. Up to 6” of insulation overlays the exterior waterproofing systems which in turn are covered with Enkadrain fabric.

The windows, skylights and doors are low-e glass which has the insulating value of triple glazing. Low-e glass reflects back into the building interior long wave length thermal radiation thereby reducing heat loss. Although there are some windows located for east and west light, most windows face south. The design of the south wall with geometric angles and light-shelves maximize winter sun gain and shade the windows in summer. The concrete construction acts as thermal storage for the winter heat gain. -- ta