Influence of personal control on thermal comfort: A psychological effect or just the "right" temperature?

Personal control of indoor environmental conditions has a positive effect on subjective thermal comfort. This has been demonstrated in various field and laboratory studies for both office buildings and long-distance transport. It is still an open question whether the perceived higher comfort was due to the belief of being in control or to the option to set the right temperature. The study was designed to examine this question in an experimental setting in a long-distance train serving as test facility. Winter conditions were simulated for 84 subjects in total who could use infrared panels and seat heating elements, respectively, to adjust their individually preferred tem-perature in addition to the centrally controlled air condition of the train. In a second experimental condition, the same heating elements were in operation but subjects were not able to control them. Instead, the individual settings of the previous condition had been restored for each subject and were administered again without the subjects' awareness. Thus, both conditions were identical except for the level of personal control.The personal control of heating elements versus the automated settings did not lead to any differences in the perception or evaluation of temperature, air draught or thermal satisfaction. Thus, the psychological effect of being in control was near zero. The "right" thermal settings appeared to be crucial, whether controlled by the subjects or by an external protocol.