The impact of window opening behavior on the indoor thermal environment and coping strategies in passive houses

China is actively developing passive houses to improve energy efficiency and reduce primary energy use. These buildings have low actual load characteristics, resulting in a smaller air conditioning terminal heating capacity. However, owing to this limited heating capacity, the air conditioning terminal provides modest indoor air regulation. In practice, occupants of passive houses often open windows for ventilation in winter, resulting in an indoor temperature that is lower than the set value, and it takes a long time for the temperature to return to the desired level. There are few studies that have investigated this issue. Two possible solutions to this issue are proposed: first, altering the external wall structure can enhance the thermal response rate, reducing the time needed for temperature recovery. Secondly, limiting the window-opening area can minimize heat loss during ventilation, thereby maintaining a reasonable indoor temperature. Notably, this may inconvenience occupants. Taking a passive house in Qinghai as a case study, this study discusses the influence of window-opening behavior on the indoor thermal environment. Simulations were conducted to study the window-opening behavior considering different window-opening areas and wall structures. Three different wall structures were considered: internal insulation combined with external insulation (IAE), sandwich insulation combined with external insulation (SAE), and external insulation structures. The results indicate that the IAE and SAE structures cannot effectively improve the indoor thermal environment after opening a window. Overall, changing the wall structure does not reduce the time required to restore room temperature. However, by limiting the opening area of the window, the room temperature can be effectively controlled. Under the given window opening ratio, the room temperature can be stabilized above 18℃. This study offers a practical method for controlling and enhancing the indoor thermal environment, which is applicable to the construction and development of passive houses.