Daytime thermal comfort in urban spaces: A field study in Brazil

Abstract

This article presents the results from thermal comfort surveys in two squares located in the city of Belo Horizonte, Brazil over two different seasons. Objective environmental parameters were compared with subjective responses collected during field surveys in order to evaluate thermal comfort conditions people experience and identify potential thermal adaptation processes. Individuals and behavioral’ characteristics were also taken into account. The summer survey was carried out in March 2013 and the winter survey in July 2013, both comprising a total of 1693 interviewees. The PET index was calibrated to determine the thermally acceptable range. Neutral and preferred temperatures, for both summer and winter, were obtained in order to assess thermal preference. The results show that people were more tolerant in one of the squares (Liberdade square) in winter, considering the same thermal conditions. These findings were associated to psychological processes related to thermal adaptation, such as naturalness, perceived control, experience (thermal history on longer timescales – seasonal) and environmental diversity - along with the presence of greater adaptive opportunities. The calibration of the PET index, resulted in the definition of the thermal acceptability range of: “Cold” for PET values bellow 19 °C; “Neutral” for PET values between 19 °C and 27 °C; “Hot” for PET values greater than 27 °C. Neutral temperatures were 27.7 °C, in summer, and 15.9 °C, in winter; while preferred temperatures were 14.9 °C, in summer, and 20.9 °C, in winter. Design strategies, such as shading, exposure to the wind and providing increased environmental diversity may improve urban environments and pedestrians' experience in cities.