Thermal comfort in offices based on office workers’ awareness of discomfort

This study aims to investigate the environment and conditions that cause thermal discomfort to occupants in office buildings. We named this thermal discomfort awareness the thermal complaint. To collect thermal complaints, an instrument was developed allowing office workers to actively express their thermal discomfort at any time. This device simultaneously measured the environmental factors of the individual's workspace. Office workers offered thermal complaints in a wide range of thermal environments. The thermal range of “Hot” complaints and “Cold” complaints were not separated; however, a difference was observed when the average values were examined. In the summer, the mean temperature for “Hot” complaints was 28.1 °C, and the mean temperature for “Cold” complaints was 25.8 °C. In the winter, the mean temperature for “Hot” complaints was 25.0 °C, and the mean temperature for “Cold” complaints was 23.1 °C. To exclude the effect of time exposed at a certain temperature, the ratio of the complaint frequency to a temperature bin was recalculated to produce a time-weighted complaint (TwC). In summer, TwC values were lowest in the range of 25.0 °C–28.0 °C. In winter, the overall TwC frequency was lower than in summer, with the lowest between 18.0 °C and 28.0 °C. This meant that residents showed a wider acceptable temperature range in winter than in summer. In addition, no seasonal differences in TwC were found in the high temperature range above 27.0 °C. However, in the lower temperature range, the TwC values were seasonally different. From these results, it can be concluded that the acceptable range based on TwC is 25–28 °C in summer and 18–28 °C in winter. From the results of this study, if heating and cooling are carried out in the direction of securing acceptability based on discomfort elimination, it will be possible to save a lot of energy by reflecting the seasonal difference.