Toronto’s cold-savvy planners adapt the city to hotter summers.
By Sam Bloch
Illustration by Meg Studer
When cities plan to mitigate extreme heat, many draw from a now-familiar playbook—more trees, more reflective surfaces, and more air-conditioning. In Toronto, city officials are exploring a different strategy: changing the orientation, massing, and materials of new buildings to improve the habitability of public space. The project, currently billed as a “thermal comfort study,” represents a new frontier in urban adaptation. “We can’t change the climate,” says Dorsa Jalalian, an urban designer at Dialog, a design firm retained for the study. “We are just trying to extend the number of hours that we can be comfortable.”
The idea that cities might shelter people from heat has a long, mostly pre-air-conditioned history, but in North America, new buildings are typically required to enhance outdoor warmth, not dispel it. In the early 1990s, when urban designers created “pedestrian comfort” guidelines for downtown Toronto, the focus was on limiting shadows and gusty winds to improve winter conditions. Back then, the city suffered an average of just 10 very hot days per year, with scant mention in the city plan. By the 2050s, that number could rise as high as 55 days.
A four-season approach to balance winter comfort and summer’s deadly heat.
In 2022—as the city prepared a broader heat relief strategy—the planning department began working with Dialog and the engineering firm Buro Happold to review those policies and update them for a climate-changed world. In the future, when a large-scale development or neighborhood plan is built, new thermal comfort requirements could encourage it to positively affect streets, parks, and other spaces by shading them at key times of the day, funneling cool breezes on summer days, or offering more vegetation. Although the city’s website foregrounds “respite during extreme heat days,” the study team also stressed the continued importance of winter comfort in an interview, for mental health and general well-being.
As an example, the project team showed LAM an analysis of a proposed buildup of towers slated for Flemingdon Park. According to Buro Happold’s in-house models, the skyscrapers would dramatically increase the comfort of the surrounding lawns and footpaths in summer but have the opposite effect in winter. For that reason, it could be rejected. “We want to be able to strike a balance so that we can maximize comfort year-round,” explains Kristina Reinders, an urban design program manager in the City of Toronto’s planning department. In this instance, potential mitigation strategies include stepping back the towers to dampen downwash or planting more deciduous trees on the ground.
Architects and academics have modeled the thermal effects of urban form for decades, but only recently has the research informed local climate policy; London, Athens, and Singapore are other global cities making the leap. If it passes, Toronto’s four-seasons approach could have its critics, including Brent Toderian, the former chief planner of Calgary and Vancouver. Once a “champion of urban light,” he says British Columbia’s fatal heat dome of 2021 forced him to rethink that assumption, and he encourages other designers to do the same. “It is more important that we address life-and-death scenarios in our summers, moving forward, than [have] ideal comfort, by the definition of urban designers, in the winter,” he says. “We’re not in a winter shadow emergency. We’re in a climate emergency.”