The average indoor air temperature (mean 28.0uC, 95% confidence interval (CI) 27.8uC-28.3uC, range 22.0uC-32.1uC) and relative humidity (mean 54%, 95% CI 53%-55%, range 27%-78%) in summer were high and had large variations consequent to opening doors and windows as the sole mode of ventilation. During the winter season when the heating system was in use and doors and windows were closed, weather conditions had less influence on the indoor thermal environment (temperature: mean 21.0uC, 95% CI 20.7uC-21.3uC, range 15.4uC-26.5uC; relative humidity: mean 40%, 95% CI 38%-41%, range 18%-72%). Data for temperature and relative humidity in rooms with different occupancy levels and out-to indoor air flow rates are shown in Table 2 . In summer, relative humidity and temperature were not different in rooms with different air flow rates. An inverse association between occupancy level and relative humidity was caused by the measurement sequence (6-person dorms were measured at the driest time in May, whereas 3-person dorm rooms were measured in July when outdoor relative humidity was higher). Outdoor climate is the dominating factor in determining the indoor temperature and relative humidity in summer. In winter, rooms shared by 6 people had the highest relative humidity and temperature at night. A low out-to indoor air flow rate was related to a significantly higher relative humidity (p = 0.000).