Last Updated: Feb 24, 2022
Even though Gord Cooke is an energy-efficiency and building-science expert and president of Building Knowledge Canada, specializing in high-performance homes and buildings, some of his family members scratched their heads when he mentioned building a net-zero cottage for the extended family.
So, he told them: "What if we had a cottage that was not only beautiful aesthetically, and a gathering place for all of our families on the lake, but was also incredibly comfortable, resilient, healthy, and our energy bills were zero," he says. "They said, 'Of course. That sounds good.'"
Their next concern was around the cost. "I said I'd cover the energy-efficiency technologies, as a net-zero home is cost-effective. If you consider the total cost of ownership over time, a net-zero home doesn't cost more to own than a standard house."
The family agreed, and Cooke and his brothers partnered with Seaman & Sons Builders to design and construct a resilient, super-comfortable, net-zero-energy cottage in Southampton, Ontario. During the process, the team shot videos of every decision made. Those videos are now part of a series available for viewing on Building Knowledge.
The project began in December 2018 and was completed 11 months later. The 2,400-square-foot family home on Lake Huron—built so three families can be together—has slab-on-grade construction. "Durability and resiliency mean no basement," Cooke says. The cottage has five bedrooms and four baths to accommodate the whole family.
The interior "has big open spaces where we can gather inside," Cooke says. "The bedrooms are small, but we're on a beach, so everyone is outdoors a lot." A summer vacation place for generations, the Cooke family has enjoyed the Southampton community since the 1920s.
Cooke and his family chose to build the cottage with ICFs (insulated concrete forms) for optimal R-values and insulation performance.
The panels, manufactured off-site with limited waste, are also easy to handle and assemble onsite. ICF also provides continuous thermal comfort without breaks on the exterior or interior.
The team constructed the cottage with R-30 blocks manufactured Amvic with expanded polystyrene (EPS) insulation. The EPS, in combination with the concrete's thermal mass, the airtightness of the wall, and the exterior and interior finishes, resulted in a wall insulated to R-30. The blocks interlock like Legos, while the walls are braced with rebar to reinforce the concrete wall.
The team also used a web-like material that, in turn, reinforces the rebar while holding the two sides together. While some minor openings still needed sealing, that effort was minimal compared to standard wall construction.
The team also decided to make any necessary penetrations in the ICF walls—for example, electrical and solar hookups, ventilation, and plumbing—before assembly. Where the team inserted windows into the ICF walls, they added reinforced concrete.
Representatives from Seaman & Sons said the home was fun to work on, in part because of the new sustainable systems and approaches Cooke implemented. For example, says Derek Seaman, "The construction process was different for us, especially on the roof where we used a lot more insulation and exterior sheathing than usual."
The wood-frame construction was nothing new, although the use of engineered lumber was. But the project also included small yet necessary actions for thermal bridging: the installation of a DuPont Tyvek system with flex wraps and straight flashes.
The low-slope steel roof with raised-heel trusses has a large beam to hold up the deck, while the slope keeps snow and water from building up and away from the house. Cooke had the house clad in limestone and engineered wood siding.
The house was sited so the family can enjoy sunsets from multiple windows. Airtight Lepage triple-glazed sliding glass doors and windows have low solar heat gain and prevent the first and second floors from getting too much sun in summer. The other Ostaco windows in the cottage are low-maintenance vinyl on the exterior; on the inside, the cellular-PVC triple-glazed windows have the look of wood.
A second-floor balcony covers the patio. "From 6:00 to 9:00 p.m. is when the sun comes directly in, and that's the time you're thinking about going indoors," Cooke explains, "so the balcony keeps the main living areas from heating up in the evening."
The steel roof supports a 10 kW solar array that powers the electricity the home uses, as well as a Tesla. The cottage's mechanicals include a Navien boiler featuring the Firetube Heat Exchanger that heats the water and in-floor heating system. A VanEE energy-recovery ventilator (ERV) keeps the indoor air balanced, fresh, and filtered.
The mechanical systems are also integrated with a Fujitsu medium-static air-source heat pump. Since the most extensive use of hot water in the cottage comes from the showers, a drain-water heat-recovery unit
Recovers about 50% of the heat, with hot wastewater going down the center of the pipe and cool water wrapping its way up and extracting the heat. The system then delivers the heat back to the boiler.
Cooke is a self-described "indoor-air quality geek." So, on the interior walls of the cottage, he specified CertainTeed AirRenew drywall.
The product is installed the same way as traditional drywall. But, AirRenew Essential has a 1/2-inch of gypsum board and a 5/8-inch Type X fire-resistant gypsum board. AirRenew Essential proactively captures VOCs through patent-pending technology, specifically formaldehyde and other aldehydes, and converts them into safe, inert compounds.
"I always worry about air quality and ventilation," Cooke says. "This product takes VOCs out of the air and sequesters them for the long term." The team installed CertainTeed Silent FX between levels with pine ceilings and wood floors.
Cooke went on to say,
“Resilience was a major theme of the cottage build, with the specter of climate change happening, we need to make houses that will last a lifetime. The net-zero technologies and construction and sustainability techniques we integrated with beautiful design that takes full advantage of lake views didn't compromise quality, design, energy-efficiency health, comfort, safety, or durability. We've built a family cottage to last for generations.”
Camille LeFevre is an architecture and design writer based in the Twin Cities.