Renderings of the proposed Passive House-standard townhouses at the Alexandra Park housing development in Toronto.Diamond Schmitt
The renderings showed a pair of townhouse complexes, with blocks of mid-rise apartments directly behind. One block contains five three-storey units with both front and rear entrances; the other, 16 back-to-back units, with rooftop terraces. The most distinguishing feature: trapezoid-shaped metal panels on the front brick façade, punctuated by modest vertically oriented windows and tapering to an entrance canopy that tilts a bit like the visor of a baseball cap.
In late May, members of Toronto Community Housing’s design review panel (DRP) convened by video-conference for their first review of the plans, which represent a small but closely watched element of the broader revitalization of Alexandra Park, a partnership between TCHC and Tridel that’s been underway for more than a decade.
The townhouses, designed by Diamond Schmitt Architects Inc. (DSAI), are a pilot project to test an aggressive low-carbon design philosophy known as “Passive House” that can slash 90 per cent of a building’s energy consumption and, in some cases, produce structures that actually supply energy into the grid. Unlike the vast majority of residential dwellings in Toronto, the 21 affordable townhouse units that will go up in Alexandra Park won’t use any natural gas for heating, relying instead on hydro and a proposed geothermal system to be located on site.
Though widely adopted in Europe, Britain, and parts of the United States, as an alternative to LEED certification, the Passive House revolution is quite new to Canada; the townhouses represent Toronto’s first such multiunit residential development. The Globe and Mail is following the project as it evolves.
Anticipating that the City of Toronto’s green building code requirements will soon contain extremely demanding low-carbon benchmarks as Toronto aims to meet its 2030 emission reduction targets, TCHC officials decided they should first develop a smaller scale Passive House project so the agency is ready to build much larger ones as its long-term revitalization program rolls out.
The DRP members were enthusiastic about TCHC’s decision. “This makes me so happy,” said vice-chair Antoine Belaieff, who also is on the Atmospheric Fund board. Others agreed, but expressed concerns about the metal panels that dominate the façade design and the brick work. “There seems to be a disconnect between those two [materials],” observed Carol Philips, a partner at Moriyama & Teshima.
DSAI associate Arne Suraga explained that his team is still exploring the cladding approach, which, he noted, is technically challenging on Passive House projects. The DRP strongly endorsed the pilot and asked the design team to come back later in the year with further refinements to the façade design and materials.
Toronto's design review panel has asked the Alexandra Park design team to come back with further refinements to the façade.Diamond Schmitt
The panel’s focus on the façade wasn’t just about aesthetics.
The design philosophy, explains Passive House Canada chair Deborah Byrne, a structural engineer at Kearns Mancini, is that the building envelope needs to be as airtight as possible, highly insulated, with triple-glazed windows and no “thermal bridging,” i.e., no beams or concrete slabs that protrude from the inside to the outside, serving as conduits for drafts.
Passive House buildings also feature sophisticated heat recovery systems, ventilation that uses fresh air and, in some cases, renewable energy features. The result is that waste heat from pipes, ducts and appliances yields enough warmth to slash energy use in the winter, while insulation and cross-ventilation maintains cool temperatures in the summer. “It’s designed using science,” Ms. Byrne says.
One of the other hallmarks of Passive House design is to minimize the exterior wall area as a means of reducing heat loss, but that means such projects tend to be boxes, as is the case with the Alexandra Park townhouses. In recent months, DSAI has been experimenting with various ideas for adding texture and variety to the facades without puncturing the building envelope.
The design team has looked to comparable ultra-low carbon projects in Sweden, by Street Monkey Architects, as well as a 100-unit affordable housing complex in Norwich, billed as the largest passive house project in Britain, by Mikhail Riches. (Energy bills for a typical unit run to about $250 annually.)
The metal panels proposed for the Alexandra Park pilot would have been affixed to the front walls using fibreglass clips, which don’t conduct heat or cold. “As architects, you have to think of ways to make the building appear interesting and engaging,” says DSAI partner David Dow, who oversees the project. But, he notes, on passive house projects, “you can’t have thermal breaks.”
Proponents say the architectural ideas behind this approach go back millennia. Buildings constructed with extensive cross ventilation and natural shadowing, using materials that retained heat or cold, were commonplace in many societies. In the 1970s and 1980s, according to an online history compiled by Frankfurt-based PassivHaus Institut (PHI), engineers and renewable energy activists built experimental zero-energy, super-insulated and often solar-powered structures in Germany, Denmark, Colorado and even Saskatchewan.
The world's first Passive House is this small complex in Darmstadt, Germany.Passive House Institute
The first official Passive House development was a small complex of four terraced townhouses built cooperatively by the property owners in 1990 in Darmstadt, Germany. The city is about 30 kilometres south of Frankfurt, which has become home over the three intervening decades to the world’s largest concentration of Passive House buildings. They run the gamut from individual homes to affordable housing complexes, day cares, schools, hospitals and office buildings. The PHI’s annual excellence award for 2020 recognized a striking new municipal building in Rouen, France, by Ferrier Marchetti Studio, in Paris.
“If you look at the adoption of Passive House in Frankfurt in the last 30 years,” there’s nothing that can’t be done,” observes Ms. Byrne, who says her firm recently completed two affordable housing projects in Hamilton and Windsor.
In North America, she adds, cheap energy has meant that architects, government agencies and developers have felt far less pressure to adopt such techniques. And compared to Europe, the market for Passive House certified building materials and specialized mechanical systems is still in its infancy, which means clients such as TCHC can encounter difficulties sourcing components.
What has become much less scarce, however, are architects, energy modellers and engineers trained to design such projects. Ms Bryne says there are now 561 certified designers and consultants in Canada, many, like her, trained overseas.
Several, including Mr. Suraga, now work for DSAI, and are glad to be putting the training to use. As Mr. Dow says of the Alexandra Park townhouses, “This is not a significantly large project for our office in terms of size, but it’s a huge project in terms of ambition because it’s setting the terms for our future.”
LEED versus Passive House
The Bolueta building in Bilbao, Spain, is the tallest Passive House building in the world.Passive House Institute
In the world of green design, it could be dubbed the Atlantic divide. In Europe, Passive House (PH) certification has increasingly become the standard of choice for governments, developers or individuals aiming to build low/no carbon buildings. In North America, the U.S. (and Canada) Green Building Council’s Leadership in Energy and Environmental Design (LEED) standard is a far more common way of certifying architecture that aspires to environmental principles.
Despite the virtuousness of the goal, the debate over which produces greener buildings is intensely partisan. Toronto architect Paul Dowsett, principal at Sustainable, characterizes the difference between the two as akin to the difference between golf (Passive House) and basketball (LEED).
With the demanding PH certification, Mr. Dowsett says, “the standard mandates maximum levels of annual total energy use, annual heating energy use and total air changes [air leakage] per hour – maximums which you can not exceed.” The goal, he adds, is to “lower the score” by finding ways to reduce carbon consumption. The certification is only granted once the building is complete and operating.
Under LEED, which offers different levels, builders aim to increase their scores by adding elements that are on the USGBC/CaGBC shopping list, including features such as water efficiency, location, materials and even “awareness and education.”
“LEED,” Mr. Dowsett says, “has been referred to as 'chasing a checklist’" and “rather than doing what is right for the building, [because] you’re looking to score the point.” Developer preferences, he adds, “heavily influence which LEED points are pursued, and which aren’t. [With PH], either the standard is achieved or it isn’t.”
Low/no carbon purists prefer PH certification. “There’s this ideology that if we target a bunch of LEED credits, we’ve done a good thing,” Deborah Byrne says. “That’s what I struggle with a lot.” But Antoine Belaieff points out that LEED has succeeded in branding the concept of environmentally sustainable architecture. “It’s a great way to create that conversation.”
Mr. Dowsett, who specializes in green architecture, goes up the middle. “My personal belief is that designing a building to both standards, LEED and PH, gives the best of both worlds as they are measuring different things.”
This is the second instalment of an occasional series following the building of Toronto’s first multiunit residential Passive House development. Next: Working with a Passive House “energy budget.”