A Net-Zero Renovation Takes a Home from Ordinary to Extraordinary
According to a 2015 report from the Senate of Canada, 17 percent of the country's greenhouse gas emissions come from buildings—including housing. That same year, Peter Darlington transformed his ordinary 1985 home in Calgary, Alberta, into a net-zero energy home.
"For me, it wasn't difficult," says Darlington, owner of an exteriors contracting firm. First, he super-insulated his 1,600-square-foot home, installed solar panels to power the home's electrical needs, and added high-performance windows and energy-efficient lighting and appliances. Soon, he was able to produce more energy than his house uses—which, he adds, "also prevented 13 tonnes of carbon dioxide per year from entering the atmosphere."
Building a net-zero house from the get-go is one way to help curb greenhouse gas emissions. From a climate perspective, though, an even better option is renovating an existing home. According to the World Green Building Council, that renovated home retains the materials and embodied energy (energy required to produce, transport, and install those materials).
In Calgary, says Darlington, most homeowners' heat is powered by natural gas. "Because our grid is dirty, our eventual goal for a net-zero [energy renovation] is to disconnect from fossil fuels altogether and self-generated renewable energy," he told Ensia.
Darlington's renovation was so successful that today he's president of another company he founded, Solar Homes Inc. His renovation is also the first Net Zero Energy home renovation labeled under the Canadian Home Builders' Association Net Zero Energy (NZE) Renovation Labelling Program Pilot. Darlington is also taking his renovation experience and sharing it with colleagues across Canada during training sessions as a member of RenoMark.
"I connected with a net-zero group after finishing my project," he says, "and also got involved with other renovators to move the field forward. Once I'd done my home, I realized how easy it is to renovate a home, and it made sense to see what I could do to help other people."
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.
Net-Zero Renovation Advice For Homeowners?
One of Darlington's challenges, back in 2015, was "researching how much energy the heat pumps would take. When I renovated my home, there weren't any energy auditors out there that could put together an approximation of energy consumption. I couldn't find any other examples in Canada of someone who'd done this. In our climate, you need to have a 200-amp service, which can be cost-prohibitive on some projects."
For homeowners considering the net-zero path to sustainability and savings, he suggests renovating your existing home. "That's the sweet spot for renovating to net zero," he says. In Canada, government rebates can partially offset the costs of energy-efficient windows and solar arrays. According to Green Building Advisor, you can achieve up to 90% energy savings for a complete net-zero renovation, including solar panels. Savings, says Darlington, can add up to $5,000 per year.
Today, Darlington still operates both companies that work collaboratively. "Solar Homes does the complete net-zero home renovation, and we subcontract my exteriors contracting firm to do envelope," he explains. "I strongly believe net-zero renovations can be scaled to fit a range of existing homes, and each project encourages and motivates other homeowners to do it on their property."
"A net-zero upgrade will save you money, and help the environment, every year for the rest of your life," he adds. Living in his renovated home, he adds, is, "from a financial point of view, exactly what we expected. We have very low, if any, utility bills. We didn't expect the comfort level we enjoy - from even temperatures to fresh air to the unbelievable quiet. It's awesome."
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Camille LeFevre
Camille LeFevre is an architecture and design writer based in the Twin Cities.