Operations on windows and external doors in UK primary schools and their effects on indoor environmental quality

This study provides a comprehensive analysis of the predictors influencing operations on windows and external doors as well as their impact on IEQ, comfort and energy. The study was carried out in 31 naturally ventilated classrooms in eight primary schools in the UK during non-heating and heating seasons. The state of the windows and external doors was collected by time-lapse cameras and visual observations. Environmental variables impacting window operations were recorded at 10-min intervals. Correlational tests and predictive regression models were used to identify how windows open area (m2) were affected by environmental predictors. Results show that operative and outdoor temperature during the non-heating season and indoor and outdoor humidity during the heating season were the main predictors of windows open area (m2). The main driver for the operation of external doors was occupancy patterns, however, the period that they stayed open was dependent on temperature. The impact of windows and external doors' open area (m2) on operative temperature decreased after 40 min, however, its impact on CO2 level was only noticeable up to 30 min. Through opening more available windows, operative temperature (34% of the time) and CO2 levels (28% of the time) could be reduced during the non-heating season. Furthermore, energy waste could be avoided 67% of the time during the heating season by reducing the set-point temperature and training school occupants on when to operate windows. This study suggests several avenues to improve the impact of controls’ operation on IEQ, comfort and energy. •This study relied on visual observations to build more valid behavioural models.•Linear models were created to show the main predictors of windows' open area (m2).•An increase in humidity would trigger occupants to close windows more.•Windows' open area was impacted by occupancy patterns and season.•The impact of open areas on operative temperature and CO2 changes over time.