Thermal comfort models and pupils’ perception in free-running school buildings of a mild climate country

Abstract In modern societies, educational buildings play a key role in creating a good social climate and conditions in which children and young people can develop. Several international studies have been conducted to evaluate students’ performance and the factors that most influence it, including classrooms’ thermal comfort. Yet, various revealed differences between pupils’ perception and the results of thermal comfort models. The large majority of the thermal comfort studies in classrooms were performed in heated and mechanically ventilated spaces. In free-running spaces, occupants’ expectations tend to be different and a lack of information was detected. In this research, data collected in 32 measurements in 10 educational spaces and 490 questionnaires were used to assess thermal comfort conditions in Portuguese educational buildings. Measurements were performed in classrooms and libraries and the sample included buildings from kindergarten to college. Global comfort was assessed by PMV index and according to EN 15251 adaptive model. In parallel, pupils’ perception was collected through specific questionnaires adapted according to their ages. The answers allowed a detailed analysis regarding the definition of the best methodology to quantify the adequate children's metabolic rate to be considered in the thermal comfort numerical analysis. It was found that when using the PMV analytical approach, metabolic rate must be adjusted and, according to the results, the best methodology is to use children's body surface area as correction factor. Generally, students felt comfortable and a large majority would maintain the indoor conditions unchanged. No perfect agreement was found between calculated PMV and the mean thermal sensation collected through questionnaires. Moreover, when comparing PMV index and EN 15251 model, PMV stands out as more restrictive.