Innovative Approaches to Mitigating Urban Heat

By Denis Koshelev

Canadian cities are experiencing unprecedented temperature increases as climate change intensifies the urban heat island effect. This creates urgent demands for innovative cooling solutions that address both immediate comfort needs and long-term climate resilience.

Research from the University of Alberta reveals that surface temperatures in Edmonton have increased by as much as 12°C compared to nearby rural areas over the past two decades. This trend is not unique, as cities like Toronto anticipate a tripling of the number of very hot days even under low-carbon scenarios.

While more measures are undoubtedly needed, a recent surge of innovative solutions is emerging to combat rising temperatures.

Applications in Canadian Cities

Canadian cities have increasingly recognized that green infrastructure represents the most cost-effective and environmentally sustainable approach to urban heat mitigation. Research conducted across Toronto neighbourhoods demonstrates that multiple types of green infrastructure applications provide measurable cooling benefits, with maximum average monthly temperature reductions ranging between 0.3 and 1.3°C. The effectiveness of these interventions stems from two primary mechanisms: evapotranspiration, where vegetation releases water vapour that absorbs latent heat from the surrounding air, and direct shading that prevents solar radiation from heating built surfaces. [2]

Toronto has emerged as a national leader in implementing comprehensive green infrastructure policies, particularly through its pioneering Green Roof Bylaw, which has resulted in over 500 green roof installations since its implementation. The city’s long-term strategic forest management plan aims to increase tree canopy coverage from 28% to 40% by 2050, recognizing that urban forests provide essential cooling services worth over $389 million annually, as shown in a comparable climate assessment completed in Louisville, Kentucky.

Vancouver’s innovative approach to urban cooling involves the strategic daylighting of historically buried creeks and streams, which not only enhances the city’s aesthetic appeal but also provides significant evaporative cooling effects. [5]

Montreal has complemented this approach by systematically replacing dark pavements with lighter, reflective surfaces while simultaneously expanding park networks in heat-vulnerable neighbourhoods. [3] [4] Montreal serves as a compelling case study for the impact of urban forests on temperature reduction. The city’s "Urban Forest Action Plan" (PAFU) was established in 2012 with the goal of increasing tree cover from 20% to 25% by 2025. More recently, the city has committed to planting 500,000 trees by 2030, one of the most ambitious targets in Canada.

Comparison of Tmax (maximum daily temperature) for Control vs GI at each location according to University of Toronto research published in the International Journal of Biometeorology (2021)

Innovative Ways of Battling City Heat

Systematic Integration of Green and Blue Infrastructure (UGBI)

Systematic integration of green and blue infrastructure (UGBI) is about intentionally designing cities so that natural elements — like trees, parks, green roofs, wetlands, ponds, and streams — work together as a network, rather than as isolated features. This approach is rooted in the idea that combining green (vegetation-based) and blue (water-based) infrastructure can deliver multiple benefits: cooling overheated urban areas, managing stormwater, improving air and water quality, and supporting biodiversity. Instead of treating each intervention as a standalone project, planners look for ways to connect these systems, maximizing their collective impact on urban climate resilience.

The results of this integrated approach are well-documented. For example, a recent review in The Innovation found that cities using a systematic UGBI strategy saw significant reductions in urban heat island effects, with parks, street trees, wetlands, and green walls providing the strongest cooling, sometimes lowering air temperatures by several degrees Celsius. These cooling effects are most pronounced during heatwaves and in densely built environments.

Blue infrastructure, such as ponds and wetlands, not only helps cool the air but also absorbs excess rainfall, reducing the risk of urban flooding. When green and blue systems are designed to work together, their benefits multiply.

Canadian research, synthesized in Environmental Reviews, shows similar trends: trees and parks are the most effective for cooling, especially in major cities like Toronto, Vancouver, and Montreal. However, there are gaps — smaller cities and blue infrastructure are underrepresented, and there’s a need for more long-term studies and better integration of health outcomes. Another review highlights that UHI (urban heat island) and urban flooding are deeply interconnected, and that systematic UGBI can address both issues simultaneously, but calls for more adaptive management and interdisciplinary research. [28] [29] [30] [31]

Urban Forests and Tree Canopy Expansion

Urban forests are a primary defence against rising temperatures, providing cooling through the key mechanisms of shading and evapotranspiration mentioned earlier. The combined impact of these processes can reduce summer temperatures by 1–5°C. Studies have shown that urban areas with more trees are significantly cooler than those with less greenery, with urban forests having daytime temperatures about 1.5°C lower than surrounding areas during summer months. The strategic expansion and management of urban tree canopies are therefore central to municipal heat mitigation plans across Canada. This involves not only planting more trees but also ensuring their health and longevity through proper species selection, planting techniques, and long-term maintenance. [8]

The cooling effect of urban vegetation has been extensively studied and quantified through various research methods, including field measurements, remote sensing, and computational modelling. A study in Montreal using a bicycle equipped with high-precision sensors found a significant temperature difference of up to six degrees Celsius between the downtown core and the greener Mount Royal Park. [9]

Another study in Montreal simulated the effects of street tree planting and found that a dense canopy could reduce air temperatures by as much as 4°C. The cooling effect was most pronounced during the hottest part of the day, between 11 a.m. and 4 p.m. Furthermore, the study found that increasing the crown diameter of trees was more effective at reducing air temperature than increasing tree height, as it provides a larger shading area. These findings show the importance of not just planting trees, but planting them strategically to maximize their cooling potential.

Green Roofs and Living Walls

Green roofs and living walls are innovative solutions that bring vegetation into the vertical and horizontal spaces of the built environment. A green roof is a roof of a building that is partially or completely covered with vegetation planted over a waterproofing membrane. A living wall, or green wall, is a wall that is partially or completely covered with vegetation. These technologies offer a range of benefits, including reducing the urban heat island effect, improving stormwater management, enhancing biodiversity, and providing aesthetic benefits. Green roofs can reduce roof surface temperatures by up to 20°C, which in turn reduces the amount of heat transferred into the building, lowering the demand for air conditioning. They also help to filter pollutants from the air and capture carbon dioxide [13].

Smart Reflective Surfaces

Canada is at the forefront of developing advanced cool roof technologies that utilize specialized pigments highly effective at reflecting invisible infrared and ultraviolet radiation. These systems go beyond simple light colours, employing engineered materials that achieve high solar reflectance and thermal emittance. A reflective metal roof can lower attic temperatures by 20-30°C compared to standard dark roofs, reducing the heat load on air conditioning systems. This leads to less frequent AC use, lower electricity bills, and longer HVAC lifespan. Studies cited in the article suggest cooling energy demand can drop by 10–20% or more. [15]

Recent research at École de technologie supérieure has developed conductive asphalt pavements using steel slag aggregates to transfer accumulated heat to lower pavement layers, reducing temperature differences and mitigating urban heat island effects. [14]

Phase Change Materials Integration

Innovative applications of phase change materials (PCMs) in Canadian urban environments show remarkable promise. Research demonstrates that optimized PCM integration can reduce energy consumption by up to 30% while improving indoor thermal comfort. These materials exploit high enthalpy changes during phase transitions, acting as thermal capacitors that absorb significant energy at constant temperature during melting. PCMs incorporated into building envelopes can store 100-300 kJ/kg of energy, providing substantial thermal buffering. [16] [17]

Biomimetic Cooling Systems

Emerging biomimetic cooling technologies draw inspiration from natural cooling mechanisms. These systems mimic termite mound ventilation for natural airflow circulation and plant-based evaporative cooling processes. Research indicates that bio-inspired cooling can reduce energy demand by up to 70% compared to conventional systems while enhancing building resilience during extreme climate events. [18] [19]

AI-Powered Cooling Management

Artificial intelligence is revolutionizing urban cooling through data-driven optimization systems. AI-powered HVAC systems can eliminate 20-40% of cooling-based energy consumption through intelligent control mechanisms. The C40 Cities (a global network of mayors of the world’s leading cities that are united in action to confront the climate crisis) collaboration with IBM has developed AI-powered tools that integrate climate, socio-economic, and spatial data to identify high-risk areas, strengthen early warning systems, and support long-term adaptation strategies. [21]

The most prominent example is Evergreen’s "AI for the Resilient City" tool, developed in collaboration with Microsoft and deployed across Canadian municipalities, including Calgary, Halifax, and Peel Region. This sophisticated platform integrates NASA Landsat imagery, Microsoft’s building footprints, infrastructure data, and local weather patterns to create comprehensive urban heat visualizations with building-level granularity.

Research applications have demonstrated the tool’s capacity to identify neighbourhoods most vulnerable to extreme heat and project future urban heat island levels with unprecedented precision, enabling data-driven decision-making for climate interventions at the micro-level. [31] [32] [33] [34]

Water-Based Cooling Innovations

Advanced misting systems represent a highly effective cooling technology, capable of achieving temperature reductions of up to 12°C through high-pressure water nebulization. These systems utilize adiabatic cooling principles, where microdroplet evaporation extracts heat from the surrounding air. The Downdraft Evaporative Water (DEW) Cooling Facade system demonstrates significant reductions in air temperature and Universal Thermal Climate Index, while potentially capturing air pollutants during the nebulization process. [23] [24]

These water-based systems are particularly valuable in Canadian contexts, where water resources can be abundant, offering sustainable cooling solutions that can be integrated into public spaces, building facades, and urban infrastructure with minimal environmental impact.

District Cooling Systems

District heating and cooling systems deliver climate control to many buildings simultaneously, often serving entire communities. These centralized systems distribute chilled water through underground networks to cool multiple buildings simultaneously. Canada has 217 district heating and cooling systems providing 2.2% of heating needs, with cities like Toronto, Edmonton, and Ottawa expanding these systems as key climate action components. District cooling can achieve up to 70% CO₂ reduction compared to individual systems. [24] [25] [26]

Super-Cool Materials and Daytime Radiative Coolers

City-scale deployment of advanced heat mitigation technologies — especially when combining reflective materials and irrigated greenery — can substantially reduce urban temperatures and energy use for cooling, offering a pathway for more sustainable and resilient cities.

Advanced urban heat mitigation technologies, integrating supercool materials with thoughtfully designed green infrastructure, effectively reduce both urban ambient and land surface temperatures, leading to significant city-scale cooling consumption reductions.

According to a large-scale heat mitigation project in Riyadh, Saudi Arabia, the most effective strategy, integrating cutting-edge materials with widespread irrigated vegetation, significantly lowered peak ambient temperatures by an unprecedented 4.5°C in urban environments. This comprehensive approach also reduced the annual sum of cooling degree hours by up to 26% from baseline levels. Advanced mitigation strategies alone decreased building cooling energy demand by up to 16%. When these strategies were combined with building energy retrofits, such as improved insulation and windows, the total reduction in cooling demand impressively reached up to 35%.

High-albedo and "super-cool" materials installed on roofs effectively lowered both surface and ambient temperatures, with super-cool materials demonstrating the greatest advantage but requiring precise placement to prevent glare. Ultimately, the most superior outcomes for reducing both temperature and energy consumption were achieved by synergistically applying reflective/super-cool materials alongside extensive, well-irrigated greenery. [27]

Final Thoughts

The challenge posed by the urban heat island effect in Canada demands a dynamic and multifaceted response. As demonstrated by initiatives from Vancouver to Montreal, no single intervention is a panacea. The most resilient and effective strategies weave together nature-based solutions like urban forests and green roofs with technological advancements in materials science and data-driven urban management. The path forward for Canadian cities lies in a holistic, integrated approach that combines these strategies, tailored to local climatic conditions and community needs.

References