Surviving the heat: What this summer taught us about urban design

Ontario experienced an intense summer of heatwaves, with temperatures soaring to near-record highs for the past decade. In dense urban areas, heatwaves are intensified by the urban heat island effect. GTHA cities became significantly hotter than their surrounding rural regions due to dense, absorbent materials like asphalt and concrete retaining and re-releasing heat from the sun.  

Green Development Standards, such as the Toronto Green Standard, have helped guide cities towards climate-conscious development that mitigates against extreme heat by requiring an array of design elements that make urban spaces better for their inhabitants. Those standards are currently at risk under Ontario’s Bill 17: Protect Ontario by Building Faster and Smarter, affecting cities’ abilities to plan and build for extreme weather. 

Designing for resilience is imperative 

The importance of designing urban environments that mitigate extreme heat cannot be overstated. By 2050, it’s estimated that Toronto will experience 66 days of temperatures over 30°C, more than triple the average between 1996 and 2010. An air temperature increase of just 2-3 degrees under extreme heat conditions can drive a 4-7% increase in heat-related mortality. While buildings that meet the legal minimums may be compliant, they risk failing in their long-term performance. Without reflective surfaces, passive cooling, and vegetation, buildings will overheat faster and rely heavily on mechanical cooling. This means higher operational costs, decreased equipment longevity, strain on the electricity grid, and vulnerability to price increases during peak demand events. 

On the other hand, high-performance buildings pay dividends: 

• Green or cool roofs lower urban temperatures, reduce stormwater runoff, and extend HVAC life spans. 
• Reflective paving, tree canopies, and urban green spaces enhance thermal comfort at street level, creating more livable, walkable environments that support community well-being. 
• Passive cooling and envelope-first design can reduce peak loads when dirtier, gas-fired peaker plants are online, saving money and reducing emissions. 

The need for integrated urban planning 

Designing resilience and efficiency shouldn’t be seen as a burden, but rather as a long-term investment in healthier communities, stronger infrastructure, and a more sustainable environment. Thoughtful and integrated urban planning and design directly shape how we live.  

Green development standards are broadly supported by constructors, developers, architects, and utilities who recognize that the way we design our cities has real-world consequences. The tools to mitigate urban heat and deliver smarter, more resilient cities already exist. They should be the baseline for responsible development moving forward.  

In response to the recent backsliding on municipal green standards, TAF recommends establishing a standardized, province-wide Green Development Standard based on the Toronto Green Standard (TGS)–a proven model that has been in place since 2010, with demonstrated benefits for energy efficiency, cost savings, and emissions reductions.