Passive window ventilation openings in every-day use

The integration of passive window ventilation openings (PWVO, small air inlets integrated in the window frame) with additional exhaust fans in the kitchen and bathroom(s) can ensure a user-independent basic air change rate in dwellings. The project reported on herein is focused on how well buildings with PWVO work in real life. Altogether 28 multi-family houses are investigated by site visits, a survey among the inhabitants and measurements in eight flats. The survey is conducted in the winter 2017/18 and addresses user ventilation behavior, thermal and acoustic comfort, IAQ and user satisfaction. The 270 completed questionnaires returned allow tentative inferences for future ventilation concepts. For instance, it is found that in dwellings heated with radiators, air draught caused by PWVO is reported less frequently then in dwellings with a floor heating. The measurements in the winter 2018/19 are twofold: short-term measurements with a focus on the volume flow rates, the airtightness and the relative pressures in the flats. Long-term measurements comprise CO2 concentrations, interior and exterior air temperatures and humidities and operation modes of the extract fans. In six out of eight flats the measured outdoor air flow rate covers only 35–80 % of the amount recommended by the Swiss building standards. The airtightness of all flats varies between qa50-values of 0.5 and 1.3 m3/(h m2) (±10 %). CO2 measurements show that in the sleeping rooms the mean is between 650 and 3′440 (±70–160) ppm. •Air draught by trickle vents is reported less often in dwellings heated with radiators.•The outdoor air flow rate per flat lies between 38 (±6) and 166 (±7) m3/h.•In 6 of 8 flats the outdoor air flow rate covers 35–80 % of the recommended amount.•The airtightness varies between qa50-values of 0.5 and 1.3 m3/(h m2) (±10 %).•The mean CO2 level in the sleeping rooms is between 650 and 3′440 (±70–160) ppm.