Abstract
In the last decades, several studies have revealed how critical the urban heat island (UHI) effect can be in cities located in cold climates, such as the Canadian one. Meanwhile, many researchers have looked at the impact of the city design over the urban microclimate, and have raised concerns about the development of too dense cities. Under the effect of the “Places to Growth” plan, the city of Toronto is experiencing one of the highest rates of building development in North America. Over 48,000 and 33,000 new home permits were issued in 2012 and 2013 respectively, and at the beginning of 2015, almost 500 high-rise proposals across the Greater Toronto Area were released. In this context, it is important to investigate how new constructions will affect the urban microclimate, and to propose strategies to mitigate possible UHI effects. Using the software ENVI-met, microclimate simulations for the Church-Yonge corridor both in the current situation and with the new constructions are reported in this paper. The outdoor air temperature and the wind speed are the parameters used to assess the outdoor microclimate changes. The results show that the new constructions could increase the wind speed around the buildings. However, high-rise buildings will somewhat reduce the air temperature during day-time, as they will create large shadow areas, with lower average mean radiant temperature.
Highlights
Several studies have revealed how critical the urban heat island (UHI) effect can be in cities in cold climates, such as the Canadian one
This has led many researchers to look at the impact of the city design over the urban microclimate, and in particular, to raise concerns about too dense cities [1]
This study focuses on the Greater Toronto Area (GTA), the largest and most populous metropolitan area in Canada, with over 6 million persons
Summary
Several studies have revealed how critical the urban heat island (UHI) effect can be in cities in cold climates, such as the Canadian one. The effects of the new constructions on urban wind environment depend on the construction location and the building facade design, it is evident that the development of high-rise buildings in Toronto is creating deeper urban canopies, while narrowing the relative street widths. In downtown, the high density of high-rise buildings surrounded by hard and dark surfaces would probably suggest higher surface temperatures, it has emerged that suburban areas within the GTA experienced higher thermal admittance properties, as common in downtown city centers It was demonstrated a strong relationship between the gross building coverage and the mean wind velocity ratio. In this sense, it was shown that the greater density of high-rise buildings in downtown Toronto could be responsible for creating vertical thermal drafts, with more releases of heat into the air [28].
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