Over-illumination

Over-illumination is the presence of lighting intensity higher than that which is appropriate for a specific activity. Over-illumination was commonly ignored between 1950 and 1995, especially in office and retail environments. Since then, however, the interior design community has begun to reconsider this practice. Over-illumination encompasses two separate concerns:

Over-illumination can be reduced by installing occupancy sensors, using natural sunlight whenever possible, turning off lights when leaving a room, or changing the type of lightbulb. Over-illumination does not refer to snowblindness, where high exposure to ultraviolet light causes physical damage to the eye. Too little light, the opposite of over-illumination, is associated with seasonal affective disorder.

Over-illumination can be caused by several factors:

In addition, there are ancillary reasons why over-illumination might be decided to be necessary. For example, retail stores with large windows will sometimes stay illuminated overnight as a method of crime prevention.

While some aspects of illumination are readily controllable, such as turning off lights when exiting a room, others are determined by the architecture and construction of the building. For example, skylights decrease the amount of artificial lighting that is required during the daytime, but most buildings do not have them installed. In addition, too few light switches can also cause issues. If an office building with large windows only has one switch per floor, then electric lights will illuminate the perimeter areas (with abundant natural light) to same level as the interior zones (which receive less sunlight).

Over-illumination has been linked to various negative health effects. While some effects might happen because the color spectrum of fluorescent lighting is significantly different from sunlight, other symptoms might be caused by light that is simply too intense. In particular, over-illumination has been linked to headaches, fatigue, medically defined stress, anxiety, and decreases in sexual function.

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