Summer Thermal Environment and Human Comfort of Shaded Outdoor and Semi-Outdoor Spaces to Living in the Urban Area of Chiang Mai City

Abstract

Outdoor and semi-outdoor spaces are important to sustainable cities because they accommodate leisure and activities of citizens, and contributing to urban livability and vitality. In the urban context of climate environments especially in summer, public spaces that provide a pleasurable thermal comfort experience for citizens effectively improve the quality of urban living. Consequently, in this paper, a quantitative field study was applied to investigate outdoor and semi-outdoor thermal comfort conditions in hot and humid tropical climate of Chiang Mai, Thailand. Thermal conditions of both spaces were evaluated based upon the measurement of major climatic parameters, while the thermal perception and thermal acceptability of subjects was captured simultaneously using a questionnaire survey. Meanwhile, the Physiologically Equivalent Temperature (PET) thermal comfort index was utilized to assess the thermal comfort conditions of selected spaces. The measurement period was conducted during the daytime from 8 am to 4 pm on April within the year 2557 BE, which is the most representative a hottest month of summer in Chiang Mai city. A total of 296 questionnaires were collected in the outdoor (72.3%) and semi-outdoor (27.7%) urban spaces during the survey, which was carried out on days with suitable weather and avoid rainy days. The majority of the respondents (99.8%) stayed under trees or buildings shaded conditions. The thermal neutrality was derived by solving the simple linear equations for a mean sensation vote of zero, which are determined by analyzing the relationship between the Mean Thermal Sensation Vote (MTSV) and PET values. The results found that, the neutral sensation PET temperatures (MTSV=0) of outdoor and semi-outdoor spaces were 27.1 °C and 28.5 °C PET, respectively. And the acceptable thermal conditions ranges were 31.0-23.1°C PET and 32.0-22.4°C PET, respectively. Compared with the thermal acceptable range between both spaces was found that the thermal acceptable range in different spaces have different thermal requirements in summer, even if they are feeling comfort.