Ventilation behavior in residential buildings with mechanical ventilation systems across different climate zones in China

A mechanical ventilation system in a residential building provides a more reliable, controllable, and comfortable means of ventilation than natural ventilation through an open window. However, the operation of a mechanical ventilation system consumes energy and may generate noise and secondary air pollutants. Thus, it is worthwhile to study residents' actual ventilation patterns. This study investigated the usage of natural and mechanical ventilation in 46 apartments across five different climate zones in China by on-site monitoring and a questionnaire survey. On average, the daily natural and mechanical ventilation durations were 11 h and 7.2 h, respectively. Large differences existed among climate regions and seasons. From north to south, as the climate became warmer, the usage of natural ventilation increased. From a seasonal perspective, the natural ventilation duration was the longest in summer and the shortest in winter. The trend of mechanical ventilation usage was opposite to that of natural ventilation. Generally, as the outdoor air temperature increased, the duration of natural ventilation increased and the duration of mechanical ventilation decreased. This study found that occupants prioritized their thermal comfort needs over healthy indoor air quality (IAQ). However, occupants were willing to spend money on energy when the health requirement could be met by mechanical ventilation. This study provides further understanding of occupants' ventilation behavior, and the results can serve as more accurate boundary conditions for analyses of IAQ, energy consumption, and thermal comfort in Chinese residential buildings.