Feeling the breeze? Ventilation practices and occupant requirements for mechanical ventilation in residential buildings

The progression of climate change and the resulting need for improved energy efficiency, as well as the impact of the COVID-19 pandemic, have drawn attention to the importance of understanding ventilation practices and mechanical ventilation systems in residential buildings. The technical requirements for ventilation systems typically consider the energy efficiency of ventilation systems as the most important criterion. However, previous research has indicated a discrepancy between the necessary ventilation practices to maximize the technical performance of mechanical ventilation systems and the actual behavior of occupants. In this mixed-methods study, indoor climate needs, natural ventilation practices and occupants' requirements for mechanical ventila-tion were examined using qualitative interviews and an online questionnaire survey carried out in the German population (N = 952). Three main findings were identified: First, our results imply that ventilation practices vary among occupants and are influenced by situational, habitual, and goal-directed factors. Second, while our sample demonstrated a range of perceptions on optimal indoor climate and ventilation practices, we identified some shared prompts and strategies across four groups. Third, occupants highly valued quiet mechanical ventilation devices that provide fresh air and filter particles, while also maintaining control over window opening. The results for system requirements partially differed according to socio-demographic variables, e.g. older occupants valued comprehensible and intuitive devices more than younger respondents. We therefore conclude that it is essential to consider occupant needs and preferences in the design and implementation of mechanical ventilation systems to optimize their operation for optimal energy efficiency.