How correlated colour temperature manipulates human thermal perception and comfort

With advanced heating, ventilation, and air conditioning (HVAC) and colour tunable LED lighting systems, indoor environmental parameters can be precisely controlled. In most colour-tunable lighting systems, the colour of light can be easily changed without increasing energy consumption. Anecdotal evidence suggests that people are under the impression that reddish light creates the perception of a warmer environment than bluish light. Although several studies have been conducted, their findings have been inconsistent. Inside an office-like laboratory climate chamber at the University of Sydney, 45 subjects were immersed in nine thermal/lighting conditions - combinations of three different room temperatures (21 +/- 0.3 degrees C, 24 +/- 0.3 degrees C and 26 +/- 0.3 degrees C) and three correlated colour temperatures (CCT - 2762 K, 3968 K and 6253 K). Using questionnaires, thermal sensation, thermal comfort, thermal satisfaction, and satisfaction with the lighting were evaluated both initially and after thermal and lighting adaptation. The results show that, in a warmer environment (26 degrees C), CCT impacts subjects' thermal sensation. Subjects judged the environment to be significantly cooler under 6253 K than 3968 K light (Z = -3.371, p = 0.001 for initial responses; Z = -3.173, p = 0.002 for adapted responses). Furthermore, high CCT light led to considerably improved thermal comfort at 24 degrees C and 26 degrees C. In a warmer environment (26 degrees C), 3968 K light positively impacted thermal comfort only after adaptation (Z = -2.883, p = 0.004 for 4000 K). The results also show that 2762 K light led to reduced satisfaction with the lighting for all temperature conditions.