How correlated color temperature (CCT) affects undergraduates: A psychological and physiological evaluation

Abstract The luminous environment had a significant influence on the working efficiency, especially for the learning efficiency of undergraduates. Correlated color temperature (CCT), as an important evaluation parameter of luminous environment, affects the learning efficiency and fatigue obviously, so it is important to select the suitable CCT for classrooms. To explore the comprehensive influence of CCT on undergraduates and thereby, find the suitable CCT in different environments for classrooms, a classroom model was built with 6 CCTs (3000K, 3700K, 4400K, 5100K, 5800K, and 6500K) under three air temperatures of 23 °C, 26 °C and 29 °C. The questionnaire survey was conducted to analyze the subjective feeling including thermal sensation, thermal comfort and CCT satisfaction for 32 undergraduates, while the experiment was done to measure the attention and relaxation of undergraduates under the different luminous environment. The questionnaire results showed that the thermal sensation vote reduced by 1.65–2.75 when CCT increased from 3000K to 6500K, and the same thermal sensation of slightly warm (TSV = 1) was achieved when CCTs were 3000K, 4400K and 5800K at 23 °C, 26 °C and 29 °C, respectively. These indicated that CCT could obviously regulate the subjective thermal perception at different air temperatures. The fitting analysis of subjective perception and physiological parameters showed that the average attention and relaxation were the highest when the thermal sensation was slightly cool (TSV = −0.40) and slightly warm (TSV = 0.59), respectively. And moderate thermal comfort (TCV = 0.03) maximized the average attention, and increased thermal comfort increased the relaxation. The suggested CCTs for learning were 4400K–5100K, 5100K–5800K, and 5800K–6500K of 23 °C, 26 °C and 29 °C, respectively. And the suggested CCTs for rest were 3700K–4400K, 4400K–5100K, and 5800K–6500K of 23 °C, 26 °C and 29 °C, respectively. This provides a comfortable and efficient lighting environment for undergraduates.