Thermal Comfort Investigation of Naturally Ventilated Classrooms in a Subtropical Region

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A field study of student thermal comfort was conducted in the Chinese subtropics. Thermal comfort affects people's physical and psychological health. The study was performed in Hunan University in China from March 24 to April 23 in 2005. Two teaching buildings were selected as study sites. Thermal comfort was measured in naturally ventilated classrooms with ceiling fans. A total of 25 classrooms were surveyed and each classroom was visited two or three times and 1273 students responded to the questionnaire. Thermal comfort variables were measured at the same time: students answered a survey on their perception/sensation of the indoor climate. Objective data analysis showed that most respondents found thermal satisfaction during the sampling month, even though the indoor air temperature and relative humidity varied greatly, with average values at 20 °C and 71%, respectively. The thermal neutral temperature calculated by Thermal Sensation Vote (TSV) was at about 21.5 °C and the slope of the regression line relating TSV with operative temperature was 0.0448/°C, which is quite different from that found in other similar thermal comfort studies. This difference is attributed to the different climate and adaptation and tolerance of students, who were the study subjects. There was a relatively large gap between studiedTSV and Predicted Mean Vote (PMV). An extended PMV model that incorporated two common forms of adaptation — reducing activity pace and expectation — was also considered, but the discrepancy between predicted and studied thermal sensations did not reduce noticeably, especially at the lower temperatures.