The degree of adaptive thermal comfort in office workers in a hot-summer Mediterranean climate

This study aims to investigate occupants’ perception of feeling comfortable over different seasons in offices located in Amman, Jordan, to determine the comfort temperature zones, and to compare the results developed from this study with other adaptive models and standards. It is based on longitudinal field surveys, which were conducted in three office buildings, two mixed mode buildings and a free running building, during four seasons: April 2016 (spring), July/August 2016 (summer), October 2016 (autumn) and January/February 2017 (winter). A total of 119 occupants participated in the thermal comfort surveys and completed 659 questionnaires. The free running building experienced a variation in operative temperature during the four seasons, while median temperatures in the mixed-mode buildings stayed almost the same during all seasons. Occupants felt comfortable in a broad range of thermal sensations from ‘cool’ to ‘warm’. Thermal comfort was expressed by a high proportion of the occupants. Occupants changed their clothing insulation with season, whereby compared to winter some occupants showed a changed clothing insulation already in the spring survey and others only in the summer and autumn survey. A Loess analysis between the temperatures at which the occupants felt comfortable and the running mean outdoor temperature indicated independency between the two variables in case of the mixed-mode buildings at running mean outdoor temperatures below 22 °C, but a trend towards decreasing comfort temperature above 22 °C. The comfort temperature in both mixed mode buildings was around 23.5 °C. In the free running building, a monotonically increasing linear relation between the two variables was found at running mean outdoor temperatures below appr. 24 °C, but a constant comfort temperature of about 26 °C above this value. Compared to the adaptive comfort models in ASHRAE Standard 55 and EN 15251 the gradient in the adaptive comfort equation resulting from the free running building in Amman was higher. Although the occupants adjusted their clothing insulation level, the gradient in the comfort equation was close to zero in the mixed mode buildings.