A rapid increase in temperature brought on by climate change is poised to cause myriad problems for city-dwellers, especially since many of us live in high-rise buildings. Though the condo booms in cities like Toronto and Vancouver have created a new generation of more energy efficient high-rise buildings (some of which present their own unique issues), there are still many structures that were built during the post-war period, when very little attention—if any at all—was paid to energy efficiency and cooling.
In Toronto alone, there are about 1,200 apartment towers were built from 1945 to 1984, now housing about half a million people. The vast majority of these units are without air conditioning. A report commissioned by Toronto's municipal government in 2015 calculated that the city can expect to experience a five-fold increase in heatwaves by 2050 compared to today. For people who live in low-income housing, the heat could be extremely uncomfortable, even lethal.
Marianne Touchie, a professor cross-appointed to the departments of civil and mechanical engineering at the University of Toronto, is studying how high-rise buildings heat up in urban environments and how we can use passive strategies to bring those temperatures down.
In post-war buildings, "even the use of air conditioners and fans is not satisfying people from a thermal comfort perspective," Touchie said in a phone interview. She's taking part in a study that monitors environmental conditions in public housing units. Toronto Community Housing, the organization that operates subsidized housing in the city for low-income residents, maintains 2,100 buildings for 110,000 people. "During the heatwave [in Toronto] last summer, over 80 percent of the suites that we monitored had average temperature of over 30°C. [These units] will become unbearable as temperatures continue to rise."
Touchie said it's particularly concerning that most dwelling spaces devoted to social housing are of the high-rise variety. These types of structures can heat up quickly, retain thermal energy, and then release it back into the living space in the cooler evenings, exacerbating the problem. She says the low-income residents who inhabit these spaces often don't have the means to seek out cooler environments, especially if their mobility is limited.
"Toronto Public Health is really concerned about that, to the point where their suggestion was to put cooling stations at some of these sites, so there's at least somewhere to go for residents without cooling in their apartments." The City of Toronto does have cooling centres that operate during heat emergencies, but they are relatively few and far between.
Another option proposed by Toronto's municipal government is to create outdoor green spaces with plenty of trees that can act as cooling zones. These would be placed in areas where there's a high concentration of apartment buildings. Not only would these spaces be designed to improve social cohesion by providing a safe space for residents to gather in hot weather, they also draw in heat from the surrounding environment, cooling down the lower floors of nearby buildings. A pilot project of this nature is being explored in Vancouver's Downtown Eastside neighborhood.
Because each high-rise building is unique, approaches to cooling need to be tailored to individual structures. Buildings that have a lot of windows facing east, for example, would benefit from new, adaptive sun-screen technologies. For those with a large footprint, installing a green roof would significantly dissipate heat. Something as simple as replacing old, single-glazed windows with modern triple-glazing would insulate living spaces against oppressive heat.
In addition, all apartment building windows in Toronto are allowed to open no more than 10 cm to prevent children from falling out. This severely limits the amount of ventilation a living space can receive. By doing something as simple as installing a grate at the bottom of the window, this opening space could be increased, providing much-needed relief for residents.
New technologies also come into play. Touchie says specialized films can be applied to windows that are customized depending on which direction they face. West-facing windows are the source of a lot of extra heat in the northern hemisphere because they collect solar energy during long summer sunsets. Special coatings can be applied that block the majority of this heat from entering the building while still allowing plenty of light to enter.
The most important change we can make to keeping buildings cool comes down to modifying our own wasteful behaviour. When we cool down our indoor environments with air conditioners or other appliances that consume electricity, the outside gets hotter. The solution to sweltering cities will come when we realize we all have a responsibility to stay cool.