Predicting of Daylight on Vertical Plane in Real Office Environment for Visual and Biological Effects
Abstract
The effects of natural light on health, welfare and productivity of employees have been known for a long time, but only recently scientists discovered the mechanism through which natural light triggers these effects (Berson et.al., 2002, Brainard and Hanifin, 2005, Lockley et.al., 2003). The human eye is sensitive to the part of sunlight spectrum between 380 and 780 nm. Photoreceptors responsible for spectral sensitivity of eye (vision) have the peak at other wavelengths than receptors responsible for regulation of circadian rhythms (secretion of melatonin and regulation of other hormones) (Brainard et.al., 2001). Recent studies of office environments confirm the connection between the quality of environmental factors (especially lighting), productivity and health of employees. A study conducted by Heschong (2003) showed that the impact of well-lit workspaces directly reflects in the performance of employees. Dogrusoy and Tureyen (2007) in his field study demonstrated that most employees prefer natural lighting and that the employees define the three most important factors of pleasant working environment as daylight, exposure to sun and natural ventilation. Mills et al. (2007) found that blue light improves productivity, Hoffmann et.al. (2008) discovered that variable light potentially improves the mood of employees in an office environment. The above mentioned studies show that circadian rhythms in addition to light also affect the productivity and mood. Existing regulations, standards, guidelines and recommendations in the field of daylighting refer to the entire visible spectrum and deal with lighting suitable for visual tasks, thus illuminances at workplane are controlled. Triggering of biological (non-visual) effects of daylight involves a different light intensity and spectral composition, and requires illumination at the eye.