Thermal perception and occupant adaptive characteristics in naturally ventilated classrooms in different tropical climate seasons: A case study in Sri Lanka

Thermal comfort in classrooms is mostly assessed in summer/hot and humid seasons; however, thermal perceptions across different climatic conditions have to be studied to undertake effective mitigation. In this study, thermal perception and occupant adaptive characteristics in classrooms of naturally ventilated school buildings were assessed during two different climatic conditions (i.e., hot-humid and monsoon seasons) in Sri Lanka. The assessments included: (1) measurements of weather parameters and (2) thermal sensation levels of students occupying those classrooms. About 879 and 852 responses were collected and assessed according to the ISO 7730 thermal sensation scale during hot-humid and monsoon seasons, respectively. Mean indoor temperatures were 30.5°C during the hot-humid season and 27.8°C during the monsoon season, while the corresponding mean relative humidity values were 75.8% and 79.8%, respectively. Findings revealed neutral temperatures of 28.5°C and 26.1°C, with comfort ranges of 25.9°C–31.0°C and 22.6°C–29.7°C, with 80% acceptability, were desired during hot-humid and monsoon seasons, respectively. The mean comfort temperatures forecasted for hot-humid and monsoon seasons using the Griffiths’ method were 28.9°C and 26.8°C, respectively. This study helps to align the design of classrooms in similar tropical climate conditions, considering the thermal comfort of occupants.