Comfortable Indoor Lighting Conditions Evaluated from Psychological and Physiological Responses

ABSTRACT

Comfortable indoor lighting conditions were examined for psychological and physiological responses. Ten Japanese males participated in a series of experiments. They were exposed to light emitted from fluorescent lamps of 2700 K in the range of 20–170 lux and of 1500–3000 lux, 3000 K in the range of 50–200 lux, 3500 K in the range of 100–200 lux and of 1200–1800 lux, 4200 K in the range of 150–550 lux and of 2500–4000 lux, and 5000 K in the range of 200–500 lux and of 3500–5000 lux and underwent two trials at 10:00 am and 5:00 pm on the same day. Illuminance at a given correlated color temperature (CCT) was first controlled at the lowest value in the designated range and then increased in a stepwise manner. On reaching the highest value in the range it was then decreased to the lowest value in a stepwise manner. Participants were required to indicate their perception of brightness, glare, and comfort at the controlled illuminances. Electrocardiogram and electroencephalogram data were monitored continuously throughout exposure. The results showed that the boundary illuminances estimated from psychological responses were not significantly different from those estimated from physiological responses. A comfortable lighting zone is expected to be a belt-shaped zone in the combination of illuminance and CCT.

KEYWORDS:

• correlated color temperature
• electroencephalogram
• heart rate variability
• illuminance