Investigating the link between CO2 concentration, thermal comfort and occupant perception in educational buildings

Thermal comfort conditions, as well as CO2 concentration in educational buildings, indirectly affect students’ attention, comprehension and learning performance. Although the standards recommend thresholds for both thermal comfort conditions and CO2 concentrations in indoor environments, the perception of students might also affect their performance. This study aims at understanding the relationship between students’ perception towards existing conditions and actual measurements. A university building, which is located in the Mediterranean climatic region of Turkey, was selected as a test site. CO2 concentration, indoor air temperature, mean radiant temperature, relative humidity and air velocity were monitored for ten days in the heating season. In addition, a survey study was conducted to understand the perception of occupants. Predicted Mean Votes (PMV) were calculated to assess the thermal comfort conditions of the classroom whereas CO2 concentrations were evaluated according to ASHRAE Standard 62.1-2016. The correlation between PMV values and CO2 concentrations were analyzed via Pearson correlation coefficient. Moreover, the effects of occupants’ thermal sensation, relative humidity and air velocity perceptions on the CO2 perception were analyzed via cross-tabulation and chi-square independence tests. The main results show that: (1) 53% of measurements exceed the recommended target value of 1000 ppm by ASHRAE, (2) there is a strong positive correlation between PMV values and CO2 concentration, (3) CO2 perception of occupants are influenced by thermal sensation as well as relative humidity and air velocity perceptions. © 2018 Society for Modeling & Simulation International (SCS).