Maximizing natural cooling infrastructure will help cities build climate resilience
Earlier this year, the Greenbelt Foundation published a new report, “Cooling Corridors: the Role of Green Infrastructure in Building Resilience to Extreme Heat,” which quantifies the positive impact that the Greenbelt’s urban river valleys have on temperature thanks to research led by Dr. Umberto Berardi, Professor, Faculty of Engineering and Architectural Science at Ryerson University, and his BeTop Lab (external link) .
Berardi’s (PDF file) working paper (external link) explores the benefit of providing tree cover to mitigate the growing problem of extreme heat. By modeling different greening scenarios applied to two heat vulnerable neighbourhoods in Region of Peel, it measures the cooling effect of tree canopy, demonstrating a considerable benefit to increasing tree coverage to reduce heat stress among urban residents. These results underscore the importance of trees as natural cooling infrastructure and the availability of shaded green spaces.
Following the publication of this report, we spoke with Dr. Berardi about natural cooling infrastructure and other strategies cities can employ to build climate resilience.
Tell me about BeTop Lab and your particular interest in this topic.
BeTop (external link) is a building science lab and research group looking at GHG emission reduction from the built environment. We work on innovative materials and do both modeling and field studies to provide high-tech solutions for a more sustainable built environment.
The recommendations in the Cooling Corridors report focus greatly on increasing tree cover. Are there further strategies pertaining to the built environment that could help to mitigate heat?
Generally, the major cooling effect of urban green infrastructure is due to the fraction of the blocked solar radiation that reaches the urban surface, and the evapotranspiration of plants and soil of vegetation and tree coverage. Accordingly, many strategies pertaining to urban green cover could be implemented in the built environment to increase urban cooling performance. Increasing the vegetation cover reduces the absorbed solar radiation by urban surfaces; it also highly reduces the reflected solar radiation to the surrounding buildings. In addition, vertical facade greenery systems add to the insulation of buildings, reducing the internal energy consumption for cooling. They also limit the exposure of the building envelope to direct solar radiation, which allows better urban behavior regarding solar reflections and absorption of urban surfaces. A similar effect can be attained by roof gardens and roof vegetation. Increasing urban water surfaces can also help in supporting the evaporative cooling effect of the local urban environment.
What are some specific policies or investments that need to be made or updated in the Greater Golden Horseshoe to strengthen and protect natural cooling infrastructure?
Policies that are concerned with protecting, preserving and increasing the natural cover have to be updated, especially within the Green and White Belts and river valleys focusing on horizontal green expansion and species protection. Protecting existing natural areas is essential. Moreover, encouraging the expansion of green infrastructure both horizontally and vertically is highly recommended.
The investment in increasing and developing green infrastructure should include both the initial cost of the fixtures and installations, as well as the long-term maintenance of the green cover. The economic value of each mitigation strategy should include the life cycle cost of the strategy, considering all maintenance, running and recycling costs. A successful financial management plan considers the district energy cost and health economic benefits to holistically indicate the impact of the greenery cover on the total neighbourhood life cycle cost.
How do you think city building can benefit from climate science? Or, what’s your vision of a city transformed by leading thinking in climate science?
Evaluating the wellness and the performance of a city will depend more and more on its response to the climatic issues. Local climatic parameters and solutions will be drivers of successful cities, which will need to find a balance between climate, nature and built environment infrastructure. Consideration of ambient thermal conditions, air quality parameters, noise control, visual pollution control, etc. is essential in urban development strategic plans.
Climatology and climate change are significant variables that affect the decision-making process in a city's growth, which should benefit from new solutions and discoveries. Preparing the city with additional cooling potential to face global warming is a wise strategy to follow, knowing that heat waves are becoming critical health issues worldwide. Beyond this, additional decisions can be taken in city planning and in the design of roads and green areas in order to shape the city's response towards climatic features and changes, and special strategies can be designed to anticipate climatic disasters, such as flood protection and rainwater harvesting.
In brief, considering climatic behavior that may impact the city's evolution is the key to building a sustainable community respecting and benefiting the environment. Overall, as we emerge from the pandemic, we have learnt the importance of clean and healthy environments and the need for cooling corridors has never been greater.