Wind, sun and temperature—Predicting the thermal comforf of people in outdoor spaces

Abstract

We describe a procedure to predict the thermal comfort of people in outdoor spaces, and show its application in determining the effects of urban height and bulk regulations around public open space in downtown San Francisco. The procedure is based on a computer model of the human thermoregulatory system, run on a typical year's hourly climate data, to produce the number of hours, by time of day and season of year, that comfort or discomfort are to be expected. The climate data are synthesized to take into account the city's influence on wind and sunlight, and are distinct for each ground-level location. The wind influences are estimated from wind tunnel tests, and the sunlight availability from one of several types of shading analysis. This procedure was used to evaluate the effect of four different levels of potential development on seven major open spaces in the city. A number of design conclusions could be drawn from the results. For the climate of San Francisco, building-induced solar blockage nearly always influenced comfort more than wind acceleration caused by buildings. This finding will not necessarily hold in other climates. The new procedure allows a more sensitive analysis of building effects on comfort than wind analysis alone.