Study on indoor air quality and fresh air energy consumption under different ventilation modes in 24-hour occupied bedrooms in Nanjing, using Modelica-based simulation

•Fresh air energy consumption of 24-hour occupied bedrooms was analyzed.•Two indoor pollutants of PM2.5 and ozone were considered.•Control capability of air conditioners under different conditions was analyzed.•A window-opening ratio of 25% (0.3 m2) could effectively improve IAQ in summer.•We recommend using natural ventilation in summer and a fresh air system in winter. COVID-19 has forced people to spend more time working and studying at home; in particular, people who share an apartment stay in their respective bedrooms almost all day. This study investigated the impact of ventilation modes on the indoor air quality (IAQ) of 24-hour occupied bedrooms and provided ventilation suggestions for people who stay in their bedrooms for a long time during the pandemic compared with the study of traditional apartment ventilation. In addition, the fresh air energy consumption of different ventilation modes was compared to help residents save energy. In summer, a window-opening ratio of 25% (0.3 m2) could effectively improve IAQ. However, it is not recommended to use natural ventilation in winter because the outdoor PM2.5 concentration is too high. Moreover, the fresh air energy consumption for the automatic control window-opening ratio was 1/5 of that for a window-opening ratio of 25%. In the whole summer, it can save 196.1 kW·h compared to a fixed window-opening ratio of 25%. Fresh air systems could greatly improve IAQ and lower energy consumption regardless of the season. However, the automatic-control window-opening ratio mode has lower energy consumption, which is approximately 0.37 times that of fresh air systems in summer.