Figs. 4e7 show the time-weighted average indoor CO2 concentration and temperature, and the proportion of opened windows/garden door in classrooms with different ventilation systems. The
proportion represented the amount of opened windows/garden door divided by total amount of windows/garden door. Figs. 4-7 showed that the windows/garden doors were opened more often in the non-heating season than in the heating season; this applies both to the automatically and manually operable windows. The percentage of manually operable windows/garden doors was lower
in the classrooms with automatically operable windows in the nonheating season, while it was fairly similar in the classrooms where ventilation was achieved by the manual opening of windows or by the mechanical ventilation system (Figs. 4 and 6). In the nonheating season, the windows were only opened in the classroom where ventilation could only be obtained by manually operating
windows (Figs. 5 and 7).