Circadian lighting design: Effects of OLED lighting conditions on visual comfort and well-being in an indoor office environment

Various lighting fixtures have been developed in response to human needs. While incandescent and discharge lamps are still widely used, newer technologies such as organic light-emitting diode (OLED) panels, which are members of the solid-state lighting family, have become more advantageous. OLEDs provide an entirely new set of artificial lighting possibilities, with numerous advantages over other artificial lighting alternatives, such as being more circadian system friendly, low power consumption, long life span, and posing no blue light risk. Lighting influences the relationship between humans and the environment in visual and non-visual respects based on human appraisals. The emphasis is on providing comfortable and healthy lighting that benefits human visual comfort and well-being in interiors. Studies on the relationship between OLED lighting and the human circadian system, visual comfort, and well-being in office interiors are limited. This thesis investigates how OLED lighting conditions affect the human circadian system, visual comfort level, and well-being in an indoor office environment. An experiment was conducted with 31 voluntary responses from the Faculty of Architecture, Çankaya University in Ankara, Türkiye. The full-scale setup office environment was designed with two different correlated color temperatures (CCT) of OLED lighting, i.e., 3000 K and 4000 K. Wrist actigraphy was used to investigate the effects of OLED lighting conditions on the human circadian system in a real-time setting. The Office Lighting Survey was used to assess the effects of two OLED lighting conditions on visual comfort, and Küller's Environmental Assessment Scale was used to assess the well-being of two OLED lighting conditions. The data collection took up a large portion of the working hours between 10:00 to 15:00, with two different days, including 3000K and 4000K OLED lighting conditions, for each participant. The collected data was then analyzed using multivariate statistical methods. Regarding the results, the human circadian system remains effective throughout the working day when exposed to warm white (3000 K) OLED lighting. In addition, warm white (3000 K) OLED lighting is more effective than neutral white (4000 K) OLED lighting in circadian rhythmicity activity and illuminance level. In terms of visual comfort conditions, the warm white (3000 K) OLED lighting is more comfortable than the neutral white (4000 K) OLED lighting. In terms of well-being, both OLED lighting conditions were rated towards the positive end of the scale; however, participants felt more calm, satisfied, curious, engaged, interested, and energetic when exposed to warm white (3000 K) OLED lighting than when exposed to neutral white (4000 K) OLED lighting. The findings of the study show that OLED lighting is effective for circadian lighting design, where they serve as an important reference for interior architecture to optimize the lighting in interiors to improve humans' visual comfort and well-being, taking non-visual aspects into account. The findings also suggest that wrist actigraphy should be used in future studies on interior architecture and lighting design to investigate the relationship between the human circadian system and different types of lighting in interiors. This could lead to interesting findings and discussions about circadian lighting design methods.