Ventilation by the windows in classrooms: a case study.

Four classrooms of two secondary schools located around Lyon in France have been monitored. The objectives are to analyse the quality of the indoor air and the thermal comfort and also the behaviour of the occupants towards opening of the windows. This paper briefly describes the context and the nature of the monitoring campaign, and presents the results of the measurements with direct interpretation of the ventilation needs. Then, we try to make a statistical analysis of the influencing factors that lead to the opening of the windows, but our study is limited because of the small number of collected data. Results from this study show that allowable CO2 levels are overpassed several times in a school day. The presence of a mechanical ventilation system leads to lower peaks but the fresh airflow is too small to prevent an indoor confining, that is also revealed by the aerobiological analysis. These measurements confirm a certain ill-being of the surveyed people, not in relation with thermal comfort. This feeling leads people to open windows provided that outdoor conditions are favourable (temperature, wind speed, noise, outside odours, ...).