How Can A Net Zero Energy Renovation Be Completed?
Super-Insulation
With his expertise in exteriors, Darlington knew how to remove the home's existing siding and insulation. Then, he applied a liquid air barrier to the sheathing. "It's like a paint you put on," he explains, "that gives you a waterproof membrane and an air barrier. It contributes a lot to airtightness." Next, he installed six-inch EPS (rigid-board or expanded polystyrene insulation),
The walls are now R-24, and the ceiling (with blown-in cellulose insulation) is R-60. In the 800-square-foot basement, Darlington insulated the walls with rock or mineral wool.
Super-Efficiency
He also installed new energy-efficient, triple-pane windows. The heat pump in the basement mechanical room draws heat out of the air and puts it into the hot water tank to heat the water. "It's awesome," Darlington says. He also installed a cold-climate heat pump. The HRV (heat recovery ventilator), for fresh air, is connected to the same ductwork as the heat pump.
Solar Success
Darlington built a new double garage with a sloping roof to accommodate 40 solar panels. "The garage also has a nice big overhang in the back that provides us with a shaded seating area," he says. "We built the garage to hold ten kW and ran that for 3 to 4 years to get some history and sense of how the systems would work together. We added more solar panels to the roof of the main house after that."
The 56 panels have a combined rating of 15.4 kW. "We're net positive," he says, "and use about half the energy our car, a Volt, takes to run." His energy bills were about $200 a month. Now, he can sell surplus electricity back to the grid.
Darlington says he paid about $50,000 for the solar panels and the new mechanicals that eliminated the need for natural gas in the house and made the home fully electric. Because the solar panels are under warranty for 25 years, Darlington says, he has estimated that his transformation to a super-insulated and solar home will more than cover those costs over that time.