Comparison of Cooling Energy Demand in Buildings that Include Cool Roofs for Three Canadian Cities

The Urban Heat Island (UHI) phenomenon is the result of increased urbanization and changes in the landscapes that leads to higher surface and ambient temperatures in cities and higher cooling energy demands. To mitigate the effects of the UHI, one technique is to use cool surfaces with high reflectivity on built environment and infrastructures. Using cool materials on the building envelope promotes reductions in cooling energy demands over the summertime and during extreme heat wave events, thereby indirectly lowering GHG emissions too. In this paper, the effects of using cool materials on steep-sloped residential roofs and low-sloped commercial roofs is investigated on buildings' energy consumptions in three Canadian cities: Montreal, Toronto, and Vancouver using the Oak Ridge National Laboratory Cool Roof Calculator. The cooling energy demands, and potential energy costs are then compared based on different values for Solar Reflectance (SR), Infrared Emittance (IE), and the R-value of the roof. The results indicated a reduction in cooling energy demands, and suggested that, for instance, in Toronto, a 10% increase in the average value for SR and IE of commercial roofs, can result in a 30% decrease in cooling costs annually. It should be noted that the extent of energy savings may vary depending on factors such as peak electricity rates, which can differ across cities and even during the day (e.g., peak, midpeak, and off-peak hours). In conclusion, there is a necessity for a comprehensive framework and the development of an inclusive tool to measure the impact of cool surfaces on energy demands and in mitigating UHI effects, with a specific focus on the roof insulation requirements observed in Canadian cities.