Master of Engineering Science
Civil and Environmental Engineering
The urban heat island is a phenomenon wherein urban areas experience warmer temperatures than their surrounding rural areas. Techniques to reduce excess heat in urban environments are known as heat mitigation or heat island mitigation solutions, with the intent that they reduce urban temperatures. This research presents an investigation on the impacts and effectiveness of urban heat mitigation techniques on improving the outdoor thermal conditions of downtown London, Ontario. The impact of increasing vegetated areas and applying higher albedo materials for road pavements is assessed with ENVI-Met software for current and future summer weather. Furthermore, investigations were conducted for current and future winter weather scenarios to explore the effects of these heat mitigation techniques on other seasons' outdoor conditions. Finally, the effects of heat mitigation strategies on building energy consumption were simulated by HAP Carrier software. Results show that increasing vegetation and trees reduce the air temperature and mean radiant temperature during both day and night periods. A higher air temperature reduction is detected for the greenery model with a higher percentage of trees relative to grasslands. The average air temperature at 17h is reduced up to 0.56°C and 0.66°C for respectively, for increasing trees and high albedo materials scenarios. Furthermore, results showed an increase in the mean radiant temperature value for the scenario with increasing albedo of the road materials. The results further demonstrated a reduction in the cooling load of buildings with increasing trees in the building neighborhoods.
Summary for Lay Audience
Urban areas are hotter than their non-developed surrounding areas. According to projections, the urban areas will be warmer over the 21st century due to global climate change and urban development. Urban heat island is an urban area with a significantly warmer temperature than its surrounding rural neighborhoods. The increasing urbanization process in cities, increasing paved areas, and decreasing green areas are the reasons for urban heat island generation. Extremely hot weather events are becoming more frequent and intense as a result of climate change. Urban heat islands during the hot seasons can lead to adverse impacts on the health of citizens and increasing energy consumption. Several solutions are proposed to reduce the urban heat island in cities, namely, increasing vegetation and increasing the heat reflectance of the road or building materials. This study assesses the impacts of increasing green areas and increasing the reflectance of road materials on the air temperature for a study area in downtown London, Ontario. The simulation software ENVI-Met analyzes the heat reduction potential of these solutions for current and future weather conditions subjected to climate change. In addition, to better understanding the impacts of these heat mitigations on other seasons, further assessments were conducted for the cold season, winter. Finally, the building energy consumption in the context of these heat mitigation strategies is analyzed by simulation. Results show that areas with low thermal comfortable conditions correspond to large flat paved areas and parking spaces without shading facilities. Increasing trees and vegetated spaces on the site can improve the outdoor thermal condition for pedestrians. Assessment of the impact of high reflectance materials on air temperature indicates that while applying these materials reduces the surface air temperature, they can cause a negative effect on the thermal comfort of the pedestrian. Adding trees in the neighborhood of buildings can reduce the energy consumption of building for cooling.
Shams, Maryam, "Urban Heat Mitigation for Current and Future Conditions: A case study for downtown London ON" (2021). Electronic Thesis and Dissertation Repository. 8098.