To achieve net zero energy:

Start with passive systems. The house design started with a tight and well-insulated envelope to augment an optimal building orientation toward the sun. Direct gain glazing covers two thirds of the long southern wall, with ceramic tiled concrete floors for direct gain heating. Trombe walls with glazing make up approximately one third of the southern wall, storing heat during daylight hours for passive distribution into the living space through the winter nights. Roof overhangs are sized to expose the southern wall to the sun during the winter, and to shade the south wall during the summer. A 37-foot (11.3 meters) passive cooling tower at the northern edge of the building, oriented and sized to maximize the benefits of the prevailing winds, combined with opened windows along the long southern wall, provides 100% of house cooling during the summer.

Augment with active systems. The passive heating and cooling components of the design work together to minimize electrical loads for heating during the winter and cooling during the summer. A grid-tied 16.8-kilowatt photovoltaic system uses 60 panels covering the south plane of the barn roof. During the LBC audit year, this system generated 20,270 kWh of electricity, of which the house and owners’ electric vehicle used 15,987 kWh. During the LBC audit period, this PV system produced a net surplus of 4,283 kWh which were pushed to the grid. Electricity loads came primarily from the following major devices (in descending order of load size): (a) Hydron Module Combination closed loop geothermal system for radiant floor heating, forced air heating, potable water pre-heating, and (almost no) forced air cooling; (b) battery charger for a 2017 Chevy Volt; (c) high-efficiency water heater which primarily uses geo-thermal pre-heated water, and the internal air-sourced heat pump as the secondary water heating method; (d) kitchen appliances and miscellaneous other appliances; (e) house lighting; (f) barn shop mini-split heating/cooling system. A heat recovery ventilator (HRV) integrated into the air system ensures fresh air within the home when operable windows are closed during the winter months.

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