analysis high-performance building
SOuth mOuntAin cO.
After one year, two of eight households used less energy than the
5.04-kilowatt photovoltaic array generated. Two other households were
very close: within about 1,100 kilowatt-hours of reaching net-zero.
n 2009 and 2010, South Mountain Co.
designed and built a cluster of eight
high-performance affordable single-family homes in West Tisbury, Mass.,
on the island of Martha’s vineyard, for
the Island Housing Trust. The homes at
All eight houses received LEED Platinum
designation and all have permanent affordability
restrictions. One of the homes was constructed
by Habitat for Humanity with technical assistance and guidance from South Mountain Co.
Half of the houses are three-bedroom units of
1,447 square feet (134 square meters) and half
are two-bedroom units of 1,251 square feet (116
square meters), all with full basements. The main
living area and upstairs bedrooms and bath are
identical in the two house types; the third bed-
room is a north extension of the two-bedroom
plan. Designed and built to be net-zero-possible,
they are all-electric homes, each with a 5.04-kilo-
watt (k W) SunPower photovoltaic (Pv) array.
Design targets ultra-Efficiency,
The houses at Eliakim’s Way are super-insulated and have unobstructed southern orientation. Basements are within the thermal envelope,
with r- 20 walls and sub-slab insulation. Above-grade walls are r- 31, roofs are r- 50 (effective
r values for the entire assembly). Windows are
triple-glazed Thermotech casements with two
low-emissivity layers and argon fill (south-facing
windows have Energy Advantage low-e coating