Health-informed Predictive Regressions and Building Materials for Decision-making in Urban Heat Mitigation
Umberto Berardi
Toronto Metropolitan University, Canada
“Saving energy and reducing heat mortality and morbidity by reducing urban temperatures with innovative approaches, which include health informed predictive regressions and innovative materials”
Over recent decades, urban areas have experienced a noticeable escalation in ambient temperature. This trend has particularly intensified in low to middle latitudes and developing nations, with reported overheating incidences in over 400 cities worldwide, exhibiting magnitudes between 0.5 and 11°C (IPCC, 2023). Several factors contribute to this rise, from anthropogenic activities to the use of heat-absorbing building materials and reduced green spaces. Compounding the issue is the prevalent use of conventional cooling technologies, which, despite their effectiveness, contribute to nearly 23% of global electricity consumption and produce significant greenhouse gas emissions (IEA, 2023).
Elevated air and surface temperatures in urban areas have direct repercussions on the well-being and health of citizens. Notably, urban overheating has been linked to increased indoor/outdoor thermal discomfort. The situation becomes critically alarming when these elevated temperatures align with heatwaves, leading to heightened morbidity, mortality, and energy poverty, especially among the most vulnerable populations. In response, a variety of urban overheating mitigation techniques, either passive (new materials) or active (new systems and energy-demanding approaches), have been proposed and tested at different urban scales and contexts.
Cool materials (CMs), i.e. materials with high solar reflectance and infrared emittance), offer a cost-effective passive mitigation solution for urban buildings by decreasing their skin temperature, enhancing indoor comfort, and reducing cooling demand. These materials, having higher solar reflectivity than traditional construction materials like concrete and masonry, are cooler in nature. The first generation of CMs, often white or light-colored, combines this high solar reflectivity with substantial thermal emissivity. These properties of CMs lead to their low thermal inertia and heat gains, minimizing the release of sensible heat. The second generation of CMs, thermochromics, adjusts its thermo-optical properties based on ambient temperatures. These materials reflect more during hotter periods but become more absorptive in colder times. The third generation enhances solar rejection by combining solar reflection with the re-emission of shortwave radiation, utilizing the photoluminescence phenomenon.
Radiative Coolers (RCs), a class of CMs belonging to their third generation, represent an emerging technology that has the potential to significantly reduce urban heat and improve indoor/outdoor thermal comfort in the built environment. Broadband and Selective Radiative Coolers (BRCs and SRCs, respectively) are the two main types of RCs that have been investigated by Dr. Berardi for application in the built environment. Being both typically characterized by high solar reflectance, the former emits thermal radiation within the overall infrared spectrum, whilst the latter emits thermal radiation mainly within the infrared Atmospheric Window (AW) wave range, a portion of the spectrum around 10 μm. A variety of both types of RCs have been developed and tested in both in-lab and in-field experimental campaigns. Most of the experiments comprise small scale specimens that do not represent real-life scale components of the built environment. Dr. Berardi is among the first researchers to have performed assessments with respect to the RCs' performance at a city scale.
The thermo-optical performance of both BRCs and SRCs is introduced and investigated simulating different scenarios representing the vast majority of urban shapes and forms. The outcomes show that both types of RCs maintain lower surface temperature and air temperature at 2 m height inside the urban canyon, compared to conventional roofs. In addition, a city scale application of RCs has been found capable of decreasing ambient temperature up to 1.6°C as potentially experienced by pedestrians.
Figure 1. Health-informed predictive regressions for decision making in urban heat mitigation with examples of materials (radiative cool materials) developed in Dr. Berardi’s group.
Finally, an integrated environmental, economic, and health-informed approach was developed as a decision-making framework to assess the associated benefits of urban heat mitigation strategies. It promotes the use of nature-based solutions, such as urban greenery cover, to mitigate the expected consequences of climate change, like extreme heat, and to promote better community resilience. The research correlates and predicts the public health records and community health metrics, such as mortality rates and emergency department visits, improvements in urban environment due to application of heat mitigation strategies This has been done through a specific and evidence-based statistical modelling that is based on community historical records. The spatial and technical accuracy are what brings novelty to the prediction technique of this tool. The statistical modelling and environmental simulation have been conducted on a neighbourhood level, increasing the prediction ability of this tool than previous trials. The health records have been predicted on a daily basis and on specific spatial boundaries. Also, the health-based modelling approach has proposed enhanced predictive regression techniques to increase model accuracy for health records prediction.
The research supports the decision-making process associated with urban development and heat mitigation strategies. The statistical-simulation tool presented in this research can be used by municipalities and local governments to assess the climate change mitigation plans and decisions. This framework presents a flexible tool for policymakers to assess sustainable action plans and local community resilience focusing on environmental, economic, and health components.
Photo 1. BeTOP group at Toronto Metropolitan University, showing Dr. Berardi (lead faculty) in the center, surrounded by graduate students in 2022-2023.
Acknowledgements and Achievements
This research has been conducted in collaboration with Friends of Greenbelt Foundation, York Region, Toronto and Region Conservation Authority, and the Government of Nova Scotia. The research has received great technical support from Statistics Canada and Health Canada and gained substantial interest from the public media. The research applied the proposed method on York Region, within the city of Toronto, as a case study where different microclimate mitigation technologies have been studied. Several results and recommendations have been presented to the policy makers and public administrations across Canada. This work helped them to identify the most vulnerable areas and urgent actions to take regarding the climate change mitigation plan. Similar collaboration and applications have been established with other local governments outside Canada to apply this framework and to extend the climate change mitigation study to include other environmental risks, for example, flooding and storm management.
