Mechanical ventilation systems aren't installed in most residential buildings in north China and the residents generally rely on opening windows to improve the indoor air quality. Heat loses drastically in minutes of natural ventilation due to great indoor and outdoor temperature difference in winter. A winter survey, including 500 random subjects interviewed face to face, was conducted in Shenyang aiming to present the opening window status of the residents, ascertain the features of indoor thermal sensation, house area, storey number, time at home, household number, feeling of indoor air quality and health consciousness and reflections of these features on the opening window habit. Furthermore, a winter test of air change rate (ACR) of opening windows, which is positively correlated to heat loss, was conducted in rooms of different sizes of a typical residential building. According to the analysis based on Chi-square (x(2)) test, subjective feeling of indoor air quality and personal health consciousness were found to be significantly correlated with residents' opening window habit. In the case of Shenyang, some rules of the effect of room size, wind direction and window opening size on ACR in winter were discovered and a few suggestions on people's opening window habit were provided. (C) 2014 Elsevier B.V. All rights reserved.