In Toronto, Ontario, Canada, pedestrian wind studies are required for new developments, as the construction of new buildings (particularly tall buildings) can influence wind patterns at grade. To properly assess these wind conditions, the local climate in the vicinity of the development must be established, as large differences in comfort conditions can result based solely on the choice of meteorological data. Within the greater Toronto Area (GTA), wind consultants have a choice between Toronto Pearson International Airport (Pearson) and Billy Bishop City Airport (Bishop). There is a tendency to select Pearson data, based on the length of the historical record and precedence; however, this decision may be incorrect based on the location of the development within the GTA. To determine the variation in pedestrian wind conditions, UrbaWind and a typical building mass were utilized to illustrate how dramatic the differences in pedestrian comfort could be.
A large tower was utilized and oriented such that the prevailing westerly winds encounter a large façade. Surrounded by low-rise suburban buildings, the tower was 25 storeys tall, with a length of approximately one hundred metres. Novus limited the analysis to the winter season, as it is both the windiest and worst season for pedestrian wind comfort in Toronto, and also shows the greatest discrepancy between Bishop and Pearson meteorological data. As the figures illustrate, the use of meteorological data from Pearson provides more favourable wind comfort conditions than Bishop.
What Have We Concluded?
This case study illustrates the significance of climatology (i.e., the correct selection of meteorological data) and its impact on the predicted wind comfort around a development. Planners, developers and architects should strive to understand the consequences and limitations of the background data involved in pedestrian wind studies. When in doubt, consider the most conservative (worst-case) predictions as being reasonable when it comes to comfort and safety.
1 – Winter Wind Conditions (Pearson)
Uncomfortable wind conditions around the northwest and southwest corners of the building. Along the west facade, wind conditions are generally suitable for standing or leisurely walking. Illustrative of the predominant westerly winds.
2 - Winter Wind Conditions (Bishop)
Uncomfortable wind conditions still located at northwest and southwest corners, but enlarged significantly. Along the west facade, wind conditions are generally suitable for leisurely or fast walking.
Shannon Testart – NOVUS
Novus Environmental Inc. is an environmental consulting firm in Guelph, Ontario, Canada that specializes in air quality and noise. The firm also conducts microclimate studies, utilizing UrbaWind as a qualitative tool to compare the effects of new construction on existing pedestrian wind comfort. The CFD allow us to predict comfort and safety based on mean or gust wind events.