On a morning-long Zoom call late last month, a team of architects and engineers tuned in from various home offices to review the latest details of a seemingly modest affordable townhouse project, slated to be the next phase of the ongoing Alexandra Park revitalization by Toronto Community Housing (TCHC) and Tridel.
In many ways, the conversation, convened by Diamond Schmitt Architects associate architect Arne Suraga, was as ordinary as the pandemic-related circumstances allowed: The participants took turns providing updates on elements such as landscaping, mechanical systems and green roof options, among others.
Yet, when the discussion turned to technical issues ranging from mechanical room placement to the procurement of construction materials, it became clear this wasn’t just an ordinary townhouse project.
At one point, Mr. Suraga ran through a series of façade renderings with options for adding texture and depth to the front-facing wall. With a “passive-house strategy,” as one participant noted, the configuration of the dwellings needs to be as box-like as possible, which means using various architectural techniques for the front wall to create a sense of depth and separation between the individual units.
Indeed, these L – a philosophy of sustainable design that can slash energy usage by more than 90 per cent. Some are so efficient and tightly insulated that passive heat from appliances, hot water pipes, bodies and sunlight provides the bulk of the warmth required, even in the winter.
Such structures come closest to delivering a climate change goal advocated by many governments, including the City of Toronto’s: zero carbon emission buildings. It’s a huge challenge. After decades of design that paid little or no attention to the energy efficiency of dwellings such as condo towers, the shift to passive-house construction will require drastic changes in the way architects and builders do their work. But as municipalities make their building codes ever more demanding, the development industry will have to adapt.
Over the coming year, The Globe and Mail will track the evolution of the Alexandra Park pilot project as it moves from the drawing board to ground-breaking. The series aims to inform the GTA development world about how to deliver such novel projects and allow the partners in this venture – TCHC, Deltera Construction Management, Diamond Schmitt and RDH, an energy modelling consultancy, among others – with an opportunity to share the lessons they’ve learned along the way.
Originally conceived in Germany 30 years ago, passive-house buildings are characterized by a handful of core traits, according to Deborah Byrne, Kearns Mancini Architects chief operating officer and chair of Passive House Canada: very thick insulation, thoroughly sealed building envelopes that allow no energy leakage, internal heat recovery devices and triple-glazed windows, which tend to be far smaller than the curtain wall windows so common in newer Toronto condos. Where possible, she adds, they’re oriented toward the sun. “It’s designed using science,” Ms. Byrne says.
While passive house has become a highly accepted approach to architecture in Northern Europe, it’s relatively new in Canada. In the past few years, however, there’s been a surge of passive-house development in Vancouver as the city adopted much more stringent building codes. A handful of affordable housing projects in Hamilton, Windsor, Ont., and Ottawa have been completed, while Kearns Mancini is in the process of designing a University of Toronto-Scarborough student residence that will be built to passive-house performance standards.
In the case of the Alexandra Park project, Michael Lam, an architect and TCHC’s senior construction manager, said agency officials realized they should look at much more energy-efficient designs after Toronto council in 2018 approved a new version of the city’s “green standard,” which not only set out tough energy performance standards on new construction, but is designed to become increasingly demanding over the next five or six years.
“When the city starts saying, we want a net zero carbon building, technically, that’s very difficult to build,” he said. “We’ve got to figure that out now.”
TCHC, he added, decided to learn with a relatively modest project – the townhouses. After putting out a call for proposals and then asking Alexandra Park residents to vote on the two finalists, TCHC selected Tridel and its construction arm, Deltera. Tridel has been TCHC’s development partner on earlier phases of the revitalization, which involves replacing a warren of townhouses with a mix of market and rent-geared-to-income units.
TCHC asked Ms. Bryne to prepare a primer on passive-house design, which she presented at the first design session earlier this year.
Typically, on relatively straightforward projects such as townhouses, the architects develop the design and hand it off to the structural engineers and the constructors. But as Fred Foo, Deltera’s senior project manager, points out, the key to creating successful passive-house projects is to involve all the professional partners (including energy modelling consultants) from the very beginning so as to head off design decisions that will undermine the building’s performance. Says Mr. Lam, “You can deliver a building with no surprises.”
Indeed, the group got an early lesson in why this kind of integrated process makes such a difference at its very first session. As one of the architects presented a series of what are called massing studies – basically, 3-D diagrams showing the shapes and set-backs of the two sets of townhouses, including some that proposed a staggered configuration – a passive house energy modelling expert spoke up. The optimal shape, the consultant said, is a straightforward box and no articulation. The reason? Minimizing the area of exposed exterior wall means minimizing energy loss.
“It was a really interesting conversation,” Mr. Lam says. But the decision raised questions about how to make a row of townhouses feel differentiated instead of monolithic. “Architecturally,” he muses, “how do you make these rectilinear buildings attractive?” (The city’s design review panel will offer its view of the proposed layout and façade treatment later this month.)
Meanwhile, Mr. Foo and the structural engineers are pushing the architects around the table to find ways of eliminating so-called thermal bridging – e.g., interruptions in exterior walls, such as balconies, that allow heat to escape and cold to enter. “The air leakage has to be zero to make these buildings perform,” he says. “The way I look at it, in terms of energy efficiency, we [are building] housing that’s wearing a winter jacket instead of a sweater.”
Mr. Lam and Mr. Foo, who have worked closely together for four years on the early phases of the Alexandra Park revitalization, say they are both excited to tackle the professional and technical challenges posed by these two townhouse clusters.
Both see it as a first step for the city’s building industry. As Mr. Lam points out, the partnership allows a private developer to gain the experience needed to build more of such highly efficient projects in the future. “This is the new reality,” he says. “The city is saying to other developers, ‘If TCHC and Tridel can do it, why can’t you?’ ”
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