The effect of thermal expectation on occupants’ response to moderate temperature ramp up: A controlled chamber experiment

Current studies on dynamic thermal environment have primarily focused on physical aspects while overlooking psychological processes through which occupants interpret dynamic conditions. This study provides the causal evidence that thermal expectation, a central but understudied psychological factor in thermal comfort theory, substantially alters occupants’ responses to dynamic warming. In a single-blinded randomised crossover experiment, 30 sex-balanced participants were exposed to two identical one-hour temperature ramps (25–29 °C at 4 °C /h) in a climate chamber. The only difference was the information provided beforehand: in one condition, participants were told the temperature would remain stable; in the other, they were told it would gradually increase. When holding constant-temperature expectations, participants reported significantly cooler sensations, higher satisfaction and pleasure levels, and weaker preference for cooling actions compared with when they expected rising temperatures. These effects occurred independently of key thermophysiological responses, as mean skin temperature and heart rate did not differ between conditions. Thermal expectation also did not alter the classic sensation-satisfaction relationship modelled by PMV-PPD, although existing thermal sensation models fail to capture these expectation-induced differences, as they assume a deterministic mapping from physiology to sensation. This study calls for a paradigm shift in thermal comfort modelling, from a thermo-physiology-centred approach towards an integrative framework that incorporates psychological factors. It provides the first causal evidence linking expectation and thermal comfort and offers novel strategies for improving occupant acceptance of dynamic thermal conditions in real buildings.