All living things adjust their behaviour to natural light. Man’s invention of artificial light has done much to enhance our night-time environment but, if not properly controlled, obtrusive light can present serious physiological and ecological problems.
Obtrusive light whether it keeps you awake through a bedroom window or impedes your view of the night sky, is a form of pollution and can be substantially reduced without detriment to the lighting task.”
The ILE guidance notes on the reduction of obtrusive light outline numerous good practices when it comes to reducing all forms of waste / spill light, mainly focused around mounting and aiming of luminaires.
When it comes to the subject of what they call sky glow, they put forward a metric called ULR which is:
ULOR / LOR
They relate the result of this equation for an Installation to certain environmental zone, numbered E1 – E4.
The ILE values are normally applied to individual luminaires rather than the installation with the mentality that is each individual luminaire complies, then the whole installation will as well.
(Taken from ILE guidance notes on the reduction of obtrusive light)
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