Decoding human perception for building indoor environmental comfort: testing the Hue-Heat-Hypothesis via physiological and psychological response analysis

The recent energy crisis limits humans’ adaptation capability to climate change in indoors, making access to active air conditioning prohibitive. Since lighting systems are less energy-consuming then conditioning systems, this work focuses on visual stimuli to affect occupant’s thermal perception in the framework of the multi-domain comfort theory. Despite the Hue-Heat-Hypothesis has already been explored, validation is still missing. The following hypotheses were outlined: (i) different coloured lights lead to changes in thermal perception that are stronger under thermally comfortable conditions; (ii) visual and thermal domains synergistically interact on the overall comfort perception; (iii) skin temperature can be used as a proxy for thermal comfort. 24 volunteers were exposed to 9 scenarios combining 3 types of coloured light (white, blue, and red) with 3 temperature levels (cool, neutral, and warm conditions). Perceptual responses were collected through questionnaires and skin temperature was measured through wearable. Results support the hypothesis that bluish lights lead to cooler sensation especially in a thermally neutral environment. Skin temperature, mainly affected by ambient temperature, was not significantly related to expressed thermal comfort, apparently in contrast with previous literature results, which may highlight an interfering role of coloured lights on investigated thermal perception as cross-modal effect.