When architect David Pill, AIA, of Pill-Maharam Architects in Shelburne, Vt., and his wife, former landscape designer Hillary Maharam set out to build their family's new home, their goal was simple: to create a house that produces zero carbon dioxide emissions, reducing their family's environmental impact, while maintaining a high level of detail and comfort. The best way to achieve this low-impact goal, they found, was to design a house that uses as little energy as possible and produces as much energy as it uses (or more) from renewable sources: a net-zero energy house.
The house Pill and Maharam created for their family was their first attempt at net-zero energy design, and despite the challenges of achieving low energy usage in Vermont's cold climate, they got it right on the first try. Their 2,800-square-foot Charlotte, Vt.-based net-zero energy residence is the first LEED for Homes Platinum-certified home in the state. It also has earned the Energy Star 5+ star rating, Vermont Builds Greener certification, and such honors as the 2008 AIA Vermont Honor Award in the House/Sustainable category; Efficiency Vermont's 2008 Best of the Best Award for houses measuring 2,000 square feet to 3,000 square feet; and most recently the Northeast Sustainable Energy Association (NESEA) Zero Net Energy Building Award.
Situated on a cleared parcel of rural land, the house maximizes energy efficiency through passive solar design and orientation, reducing heating and cooling needs, along with high-efficiency windows and a tightly sealed, superinsulated building envelope. To reduce energy loads, Pill and Maharam combined the simple forms and mass of the region's farmhouse vernacular with an open plan that allows daylight to flow throughout all living spaces and a concrete slab embedded with hydronic tubing for thermal massing and in-floor radiant heating. A ground-source heat pump and high-efficiency lighting and appliances further reduce the house's energy demand.
"We tried to get the energy load down to the lowest possible level before we applied a renewable energy source," Pill says. "We happen to have a good wind site, so we chose a wind turbine." The 10 kW net-metered turbine generates enough energy to power the home's heating, hot water, lighting, and appliances, and still creates enough surplus energy to feed back into the electrical grid.
From January 2008 through January 2009, the Pill-Maharam residence used 6,094 kWh of electricity. Its wind turbine produced 6,286 kWh of electricity, sending 192 kWh back into the electrical grid. According to Pill, his family burned about 175 kWh's worth of wood in the house's wood stove to supplement the geothermal system's heat, making the total net gain 17 kWh. With the addition of foundation insulation, the home has since produced even more surplus energy. From March 2008 through March 2009, the house's turbines had produced an extra 506 kWh.