In 1985, the city of San Francisco adopted a wind comfort standard in its Downtown Area Plan in response to increasing concerns about the city’s downtown open spaces becoming excessively windy. It was perceived that many of the spaces open to the public had become uncomfortable places to walk or stay due to winds and shade induced by surrounding high-rise buildings. A side effect of the “Manhattanization” of San Francisco in the 1960s and 1970s, during which a majority of the high-rise buildings that dominate the city’s urban skyline were constructed, these standards were put in place but never re-assessed.
After 30 years of implementation, a recent study co-authored by Associate Professor of City & Regional Planning, Landscape Architecture and Urban Design Elizabeth Macdonald and Hyungkyoo Kim, Assistant Professor at Hongik University revisits the wind comfort standard, examining its effectiveness in promoting pedestrian comfort. “Measuring the Effectiveness of San Francisco's Planning Standard for Pedestrian Wind Comfort” analyzes 701 valid samples collected from 6 months of field study at four locations, which combined surveying pedestrians and on-site collection of microclimate data.
Statistical analysis and an assessment using the physiological equivalent temperature (PET) showed that 11 mph (4.92 m/s), the comfort criterion in places for walking, performed as an effective determinant of outdoor comfort in San Francisco. Using the PET, the researchers were able to verify that the temperature at which people feel thermally neutral or acceptable has to be higher when the equivalent wind speed (EWS) is above or equal to 4.92 m/s than when it is below the criterion.
Overall, the paper concludes from the findings that the criterion operates well as a determinant of outdoor comfort for San Francisco’s public spaces. The research sheds light on the question of climate-resilience in cities as a key urban challenge.