By Daniel Berg and Michelle Ong
We recently built a net-zero energy Passive House in the Dogtown neighborhood of St. Louis. The Passive House designation indicates adherence to very strict guidelines regarding heating and cooling load, overall energy use, and air leakage. This is the first passive house in the state of Missouri.
Several features contribute to its efficiency:
Siting: the house is sited to take advantage of passive solar gain. The southern windows are relatively large while the northern windows are small. Awnings are sized to block out summer sun, but allow in low winter sun.
Insulation: The walls are built using insulated concrete forms. These are hard foam “legos” with hollow cores filled with cement. The roof is made of pre-fabricated structural insulated panels. These have particle board on either side and thick foam in the middle intermittently strengthened with wood. We also have two thick layers of insulation under the foundation. Foam under the foundation is important to prevent loss of energy to the ground surrounding the house. There is also very little air leakage. All areas with leaks were found using a smoke device, then sealed with foam. In order to maintain good air quality there is an energy conservation air exchanger.
HVAC systems: The house uses a ground source heat pump for heating and cooling. Fluid runs though a loop of hose vertically buried 100 feet outside the house. A heat pump takes advantage of the consistent 55 degree temperature of the fluid to heat and cool the house.
Energy systems: The house uses no gas, and is completely powered by a grid-tied 4 kw solar energy array.
Key participants have been Ralph Wafer, architect, Anthony Garavaglia of Trumpet, Gary Steps of Butterfly Energy Works and Greg Swetz of BRC Builders/ICF Missouri.
Dan and Michelle are long time Sierra Club members.