Project: NetZero Precast Concrete Duplex
Cost: Not disclosed
Location: Edmonton, Alta.
Contractor: Lafarge North America Inc.
Architect, engineer: Stantec Inc.
The winner of Alberta Construction Magazine’s Top Projects Awards’ Project of the Year is also the winner in the Sustainability category—and for good reason.
The NetZero Precast Concrete Duplex project in the Riverdale community of Edmonton, created by Lafarge North America Inc. in partnership with the architecture and engineering firm Stantec Inc., is the first of its kind in Canada. The judges were especially impressed with the partners’ goal of designing and building the ultimate energy-efficient structure—one that could serve as a model for future sustainable housing development.
The two-year project, built for Habitat for Humanity, began in October 2011. Two families received their keys to the units on October 17.
The duplex has been designed to be a net-zero structure—meaning that it will create enough energy to cancel the amount of money needed to heat, cool and power the structure. That will be achieved by generating solar power and using geothermal energy, which can be returned to the power grid for storage.
The heavy emphasis on sustainability is why the project is targeting LEED Platinum certification.
To ensure that there is an air-tight and energy-efficient building envelope, it was decided that the primary building material should be precast concrete rather than wood, steel or another common building material. Lafarge fabricated the duplex’s wall panels at its Edmonton plant, and then transported them to the construction site for assembly.
Volunteers erected the walls and roof in June 2012.
Lafarge ready-mix concrete was used to pour the duplex’s foundation, and to provide a two-inch layer of topping over the precast hollow core slabs.
The structure’s exterior insulated precast panels have an insulation rating of R44 for the walls and R88 for the roof. As a point of comparison, most homes are R16–20, so the precast concrete envelope is expected to provide three times the insulation of a typical home.
Concrete also makes the structure safer in the event of fire, increases sound resistance and reduces the amount of on-site construction waste. To help it meet its net-zero classification, the duplex also features a geothermal heating and hot water system. Photovoltaic panels on the roof generate solar electricity.
Researchers from the Massachusetts Institute of Technology will monitor the building’s energy performance for the next two years to determine if the high-efficiency design delivers on an operational basis. As well, Lafarge plans to use the lessons learned in this project in future projects.
Finally, it is worth noting that sustainability is not limited to the duplex’s construction. The Habitat for Humanity program is itself sustainable. Habitat families pay an interest-free mortgage, which is amortized to 25 per cent of their income, making Habitat homes affordable. The mortgage payments are reinvested into building more Habitat homes. Families also contribute 500 hours of sweat equity on the build sites as their down payment. ■