According to several recommendations and scientific studies the perceived air quality improves with increasing outdoor air supply rate. And there seems to be an upward trend in the recommandations:  A few months ago, I saw 25 l/s/person mentioned as the lower limit for outdoor air supply to avoid Sick Building Syndrom.

On the other hand many buildings with natural ventilation have a very low supply of outdoor air during winter time - some times probably less than 0,1 air changes per hour (excl. infiltration). And in a number of these buildings the users seem to have a positive perception of the indoor air quality. Is there a psychological factor involved?

Obviously it is very important for the energy consumption in the ventilation system that you limit the outdoor air flow flow rate during the cold season. But - as indicated above - it is not easy to assess the right figure.

What is your opinion/experience?