The effects of brightness and prominent colors on outdoor thermal perception in Chongqing, China.

Outdoor thermal comfort has become an important factor affecting human mental and physical health due to rapid urbanization. This study aimed to investigate the influence of brightness and prominent colors on thermal perception in hot summer and cold winter regions. Meteorological measurements were conducted accompanied by subjective thermal and visual questionnaires (n = 2020) during summer and winter. The physiological equivalent temperature (PET) was applied as thermal indices to evaluate the influence of visual conditions on thermal perception. The results showed that (1) the neutral PET is 20.2 °C with a range of 14.8 ~ 25.7 °C in Chongqing and neutral illumination range is 0 ~ 8663 lx. (2) Thermal sensitivity is most great in neutral brightness than bright and too bright groups. The influence of outdoor prominent colors in winter supports hue-heat hypothesis. However, in summer, result only supports the hypothesis under low thermal stress. Both cool and warm colors can reduce the thermal sensitivity of visitors compared to neutral colors (gray and white). (3) The interactions between colors and brightness are more obvious under low thermal stress levels. (4) Thermal perceptions of females are more greatly affected by brightness and prominent colors compared with males. These results could help landscape designers better understand the correlation between the thermal and visual environments and provide a reference for comprehensive designs of urban open spaces.