Effects of air temperature, illuminance and correlated colour temperature on the psychological and physiological responses of young females in summer

Achieving thermal comfort while maintaining energy efficiency in buildings requires an integrated approach that includes both Heating, Ventilation, and Air Conditioning (HVAC) and lighting systems. This study examined the combined effects of horizontal illuminance, correlated colour temperature (CCT) and air temperature on human thermal perception under steady-state conditions. Fifty-four healthy young female participants were exposed to three air temperatures, six illuminance levels and five CCT settings in an artificial climate-controlled chamber. Physiological responses were measured using mean skin temperature, whereas psychological responses were assessed using subjective thermal sensation and comfort ratings. Results showed that mean skin temperature increased with air temperature but was unaffected by illuminance or CCT, indicating physiological thermal neutrality under all visual conditions. Thermal sensation increased with both air and skin temperature. Psychologically, low-illuminance levels consistently reduced perceived warmth and improved comfort, especially under warmer conditions. CCT had limited influence on thermal sensation, but warm-toned lighting enhanced comfort in slightly cool settings. These findings suggest that warm-CCT lighting may enhance comfort in cooler environments without additional thermal load.