Thermal Comfort Assessment in Classrooms in the Hot and Dry Climate of Iran Field Survey in a Primary School of Kashan

In modern societies people spend over ninety percent of their time in indoor spaces. Children spending more time at school than any other building except at home evidences the importance of providing comfortable indoor thermal conditions in schools. Thermal comfort since has been related to productivity and wellbeing in schools has gained importance in recent years. Several studies have shown that the international comfort standards for buildings and the related prediction models report a warmer sensation than the occupants report especially in the case of naturally ventilated buildings in warm climates. Indoor Thermal comfort assessments provide valuable information for architectural design although the many parameters integrated in the process usually makes the assessments complicated. Thermal comfort in classrooms due to the specific activity levels and clothing of girl students due to regulations in Islamic countries as Iran and also limitations for adaptive behaviors is important and needs to be studied extensively. Not many research has been done in the field of thermal comfort in educational buildings especially in primary school in comparison to office buildings over the world and due to the contextual dependency of thermal comfort studies, results cannot be generalized.  In this study microclimatic conditions including the air temperature, relative humidity, mean radiant temperature and air velocity were recorded with instruments following ISO7730 requirements over a school day in May2013 in two non-air conditioned classrooms with operable windows located on the north and south side of a new built primary school in Kashan, a city located in the hot and dry climate of Iran.  Fanger’s indexes PMV and PPD were calculated based on the measured data every hour from 7:30 to 13:30. In addition to physical measurements, subjective assessment has been undertaken. Sixty 10-11 year old girl students were surveyed regarding their thermal sensation, overall comfort and thermal preference in the two classrooms three times by means of two questionnaires, one related to actual microclimatic conditions and one related to occupant-building interactions. The AMV and DISS indices were attained from questionnaires.  In addition reactions to discomfort were observed and recorded over the class hours. Results have been compared with ISO7730 and ASHRAE 55 standards. Results indicate that the thermal conditions in the surveyed classrooms are almost unacceptable in total class hours in both of the classrooms and not within the comfort ranges provided by standards. Although the south classroom was about 1.5 ° warmer due to solar gain through windows during class hours.  The difference emerged from PMV and the AMV (difference between the instrumental data and the questionnaire) highlighted the importance of thermal adaption of students in classrooms. Also the applicability of the adaptive comfort model was investigated by comparing the subjective responses derived from the survey with the equation used in the ASHRAE standard 55 and Heidar's comfort temperature equation derived from field studies in Kashan. It has been concluded that due to behavioral limitations students face for adapting with thermal conditions in classrooms architects should focus on design strategies for providing thermal comfort in classrooms.