Caroline Hoffmann, Achim Geissler, Claudia Hauri, Heinrich Huber
Languages: English | Pages: 10 pp
Bibliographic info:
40th AIVC - 8th TightVent - 6th venticool Conference - Ghent, Belgium - 15-16 October 2019

In Switzerland, 70 % of building refurbishments are realised in stages. When only a window replacement is done, the new airtight windows can lead to a reduced infiltration air exchange and subsequently there may be moisture issues, e.g. mould. The integration of passive window ventilation openings (PWVO) with additional exhaust fans in the kitchen and bathroom(s) can ensure a user-independent basic air change rate. PWVO can be defined as small air inlets integrated in or near the window frame. These inlets enable a basic air exchange due to the pressure difference between inside and outside. This project is focused on how well buildings with PWVO work in real life. 
Altogether, four newly built and eight refurbished building types (in total 28 buildings) are investigated by site visits, a survey among the inhabitants of the buildings and measurements in eight selected flats. 
The survey is conducted in winter 2018 and addresses topics like user ventilation behaviour, thermal and acoustic comfort, IAQ, obtained information about the PWVO and user satisfaction. All questions refer to the winter period. The 270 answers to the survey allow tentative inferences for future ventilation concepts. It is found that the operation mode of the fan (permanently or intermittently) does not affect the user acceptance. If PWVO are combined with a heat distribution by radiators air draught is less likely than in connection with a floor heating. The air draught risk is also reduced by using PWVO in the window rebates (+ radiators) instead of PWVO top-frame. PWVO with fixed openings are rated similar to adjustable PWVO. However, users do not mask the latter. A user information helps to prevent occupants from opening the windows for a too long time in winter.  
Two types of measurements followed winter 2018/19: firstly, short-term measurements with a focus on the volume flow rates (supply and exhaust air), the airtightness of the flats and the relative pressures in the flats. Secondly, long-term measurements comprise CO2 concentrations, interior and exterior air temperatures and humidities and operation modes of the fans. In seven flats the fresh air supply rate per flat lies between 38 and 166 m3/h (±5 %). Based on room use related requirements, one flat has an adequate air supply and one an oversupply. In five flats only between 35 and 81 % of the demand is covered. The airtightness of all flats is good (qa50-values: 0.5 - 1.3 (±10 %)). CO2 measurements show that in the sleeping rooms the mode (22:00 – 06:00 h mean) ranges between 700 - 800 and 1´000 - 1´200 ppm.