Daylight, artificial light and people in an office environment, overview of visual and biological responses

Long-term behaviour/response of people has been studied in standard window zone offices during daytime working hours. Regular cell-offices were equipped with experimental lighting systems delivering lighting conditions that are known to influence human physiology. The results show that most people prefer to follow a daylight cycle instead of a constant level. Preferred lighting levels are significantly higher than today's indoor lighting standards and correspond to levels where biological stimulation can occur. The results strongly suggest that meeting biological lighting needs is very different from meeting visual needs. Results of two permanent occupants show striking differences in lighting settings, which correspond to individual circadian cycles and performance. This strengthens that present indoor lighting levels (and standards) are too low for biological stimulation. Medical research has shown that a prolonged lack of 'light vitamin' can cause health problems ranging from minor sleep and performance difficulties to major depressions. This inevitably suggests that 'poor' indoor lighting is the underlying cause of many of the health and performance problems. By naming this the 'ill-lighting syndrome' we may well have identified the fundamental mechanism that can result in many different negative health/performance effects. Creating healthy indoor lighting can be a simple form of preventive medicine and providing a new challenge for the lighting community.