Mechanical ventilation in housing: understanding in-use issues

Continuous mechanical ventilation (MV) in housing can in theory secure recommended air change levels without depending on control by inhabitants or on uncontrolled air leaks. Numerous in-use issues related to continuous MV systems have, however, been identified through field studies. The gap between design intention and actual performance and use of continuous MV should be narrowed as far as possible to reduce energy use and increase the inhabitants’ health. This paper proposes a process diagram linking the emergence of ventilation practises with factors related to both the occupant (tacit knowledge, learning and needs) and the dwelling (design and procurement). Steps of the process are identified where the performance gap in relation to the continuous MV may gradually build up and lead to MV being ignored in a domestic context – that is, failing to secure the necessary maintenance or even switching the system off permanently. The diagram is based on findings of previous studies as well as results of a 1-year-long in-depth building performance evaluation of 40 households in two UK developments.