On a building site in Brantford, a Canadian town southwest of Toronto, a new house will soon be built using an approach that’s a little more like putting together IKEA furniture than traditional home construction. Designed to Passive House standards—an ultraefficient system that saves energy—the house is a new experiment for Habitat for Humanity Canada. The organization relies on volunteer labor, and the new design makes it easier for volunteers to build. It could also help make sustainable-home construction more affordable.
The nonprofit, like others in the homebuilding space, is dealing with construction costs that have sharply risen. The new design grew out of a conversation about fundraising. “They were relying on traditional construction methods to build houses, rather than optimizing that process and leveraging the great volunteer workforce that they can bring to projects,” says Sumit Ajwani, founder of Makers, a creative consultancy that partnered with the nonprofit on the experiment, called the Upstart Project. “It was clear that there was an opportunity to make a more affordable, better home, that also better uses their volunteers.”
Instead of framing the house on the building site, the Upstart Project design uses prefab parts that can be built inside during the winter, when weather puts a halt to construction outside. When the pieces of the house are put together onsite, it requires less specialized labor because components like walls are already assembled when they’re delivered. “You can modularize the components themselves, so that they become really easy pieces for volunteers to put together,” says Craig England, founder and principal at Passive House 43, a Toronto-based architecture firm that worked on the design. “Instead of overwhelming them with framing a whole home, they’re really just framing a panel.”
[Image: courtesy Habitat for Humanity]
“Panelized” walls built offsite include the interior wall, a couple of layers of insulation around a vapor-control layer to keep moist air inside, and the exterior shingles. Once they’re trucked to the site, workers just have to put the walls in place. A passive-house design requires that the building envelope—the separation between the interior and the outdoors—be airtight to save energy, which can be challenging to construct without specialized experience. The prefab design helps simplify part of the process. “It accelerates the site work, especially on the complex side of getting the building envelope correct for something like a high-performance build,” says England.
The passive-house design can help significantly reduce energy bills. The new house, which will have a heat pump but not a furnace, is expected to use 76% less energy for heating. An average house in the area might have an electric bill of $100 a month, but the new home will likely have bills between $11 and $25 per month—something that’s particularly helpful for the low-income families that qualify to buy Habitat for Humanity houses.
Other tweaks in the design also help make on-site construction easier. If ceilings are nine feet high, for example, it requires cutting lumber to make walls the right size, “but if you build everything in eight-foot spans, there’s no cutting,” says Ajwani. “So suddenly, it’s way easier for someone to assemble, say, a panel, or part of a house.” Services like electricity and plumbing are …….