The objective of this study was to identify the relation between occupants' daily activities and window control and also to quantify the influence of environmental variables on occupants' window opening and closing behavior. A field measurement was carried out during non-heating period, from February to May 2015, and heating period December 2014 to February 2015 in twenty occupied housing units. Window state, indoor and outdoor environmental conditions were continuously monitored during the measured periods. From the results of the field measurements, it was found that the control of window is strongly related to occupants' daily activities. Cooking, cleaning and getting fresh air accounted for 27%, 40%, and 33% of total openings, respectively. Window opqnings in relation to the activities occurred at the specific time during the day. The daily average opening frequency and opened hours were varied from 0.5 to 1.8 numbers/day and from 0.4 to 0.6 h/day respectively depending on outdoor temperature. The proportion of opened windows steeply changed when outdoor temperature exceeded 12.7 C. Window closing was associated with the degree of drop in indoor temperature after windows were opened. The results of this study can help developing a complete model inferring occupants' window opening behavior in residential buildings. (C) 2016 Elsevier B.V. All rights reserved.