Status of thermal comfort in naturally ventilated university classrooms of Bangladesh in hot and humid summer season

Abstract

Indoor thermal comfort is dynamic because of complex interactions between occupants, season-specific climatic parameters, and region-specific socio-cultural setup. A thermally comfortable environment is a key requirement for obtaining good classroom performance. Providing adequate thermal comfort is considered to be the greatest challenge in naturally ventilated (NV) conditions in tropical cities during the summer season. Present study is focused on assessing student's thermal perceptions and behavioural adjustment in NV university classrooms within the tropical-wet climatic zone in Bangladesh. Field surveys consisting of 24 observations were made during the peak summer in 2017, and 579 data sets were collected and analyzed. The mean indoor air temperature, relative humidity, and wind velocity were observed at 30.9 °C, 78.4% and 0.8 m/s. We used a linear regression model to estimate the neutral temperature, but Griffiths predicted mean comfort temperature (27.8 °C) was found to be more relevant to the classroom environment and the sample size. About 43.7% of Students voted within two central comfort bands (0 and + 1) on the ASHRAE thermal sensation scale having a temperature range of 27.5–33.8 °C. Hence, we compared student comfort temperatures (Tcomf) obtained from Griffiths method with the existing thermal comfort models. About 87.7% and 81% of students Tcomf was observed within 80% and 90% acceptability zone of ASHRAE standard 55 respectively. Moreover, about 89.3% and 95.9% of the students' Tcomf was found within Category II and Category III comfort bands of CEN (EN 15251), respectively. Results indicate that students are comfortably adapted to the extreme weather during summer.