Occupant response to passive stack ventilation: a UK postal survey.

A study was set up to compare the effectiveness of passive stack ventilators (PSV) with mechanical extract fans (MEF) in providing adequate ventilation in UK homes. New build and refurbished homes with PSV and MEF were identified and questionnaires posted to 3000 households of which 1223 were returned. The survey showed that in homes installed with a PSV system, only 7% of those in the kitchen and only 8% of those in the bathroom were reported as blocked up. There were also few cases in which the MEF was blocked up or disconnected: 1.5% in kitchens and about 5% in bathrooms. However, less than a half (40%) of the respondents "usually or always" used their MEFs whereas most (93%) of the PSV systems were in constant use. The respondents were asked to rate how problematic condensation, mould and noise were in their home. Approximately one-third of the respondents had at least a moderate problem with condensation in winter (34%) and noise from extract fans (36%) and one-fifth (19%) had moderate problems with mould. Fewer occupants had problems in homes installed with a PSV system than homes fitted with a MEF, whether manually operated or humidistat-controlled.