Tom Southworth’s Super-Insulated Home Goes Beyond Net Zero
Wednesday, June 15th, 2011
Tom Southworth’s BEYOND net zero home will sell power to the grid each year!
Tom Southworth’s commitment to sustainability runs deep. Since 1974 he’s owned and operated a water-powered sawmill in Lancaster, New Hampshire, around which he built the successful Garland Mill Timberframes business. Tom imparted his passion to his son Ben, whose work includes turning a 1970s ranch house into a LEED Platinum, Net Zero showcase. So when it came time to build a home to retire in, Tom set his sights high: he wanted a house that would not only generate all of the electricity it uses each year, but also produce a surplus to sell to the grid.
New Hampshire Ups the Ante
“What got me started in this direction is when New Hampshire went beyond net billing and offered to write me a check if I produce more power than I use,” Tom says. “I took a hard look at my energy usage and determined that 8,000 kWh/year would allow us to meet all our needs and be a net exporter of electricity.”
Most impressive is that Tom both exports power to the grid and heats his home with electricity. While conventional wisdom is that electric heat is expensive, 21st century building standards challenge that assumption completely.
“While it’s not official yet, we built this house to meet German passivhaus standards,” Tom says. “This means an extremely well-insulated building envelope consisting of 12″ exterior side walls packed with cellulose sheathed with 2″ foam, and 40″ of cellullose packed into the truss system. We moved in on April 1st and so far have not used any heating whatsoever.”
Tracking Results
Tom Southworth’s solar thermal storage tank is tied into its own electric meter to track run time of the backup electric element
To keep track of his goals, Tom uses a decidedly analog but very effective method of monitoring his systems – an extra electric meter dedicated to tracking photovoltaic production, and a second dedicated to his hot water tank. In addition to the photovoltaic system, Tom had us install a solar hot water system tied into an existing 120 gallon storage tank with electric backup.
“Since we don’t really know much electricity our backup tank will use in the winter, we added the second meter so we could really understand it,” Tom says, “We expect to use only solar-heated water from May through September and will be closely watching how much the electric element is needed in the other months.”
Power While the Sun Shines
Now that everything is up and running, Tom says the system is so far “on target” for photovoltaic production.
“I’m 100% pleased with the system,” Tom says, “I look forward to enjoying my years of retirement knowing my energy comes from the sun.”
