The term “BUG” was developed by the Illuminating Engineering Society (IES) and International Dark Sky Association to calculate the stray light that escapes from an outdoor light fixture. It is a comprehensive system to replace the original, “cutoff” system that applied solely to street lighting. With more and more outdoor lighting fixtures being developed, the BUG classification system is a tool to evaluate the light output of outdoor lights.
What’s the Means for B, U and G? Let’s check the below explanation.
-Backlight, which creates light trespass onto adjacent sites. The B rating takes into account the amount of light in the BL, BM, BH and BVH zones, which are in the direction of the luminaire OPPOSITE from the area intended to be lighted.
-Uplight, which causes artificial sky glow. The U rating takes into account the amount of light into the upper hemisphere with greater concern for the lower uplight angles in UL. Lower uplight (zone UL) causes the most sky glow and negatively affects professional and academic astronomy. Upper uplight (UH) is mostly energy waste.
-Glare, which can be annoying or visually disabling. The G rating takes into account the amount of frontlight in the FH and FVH zones as well as BH and BVH zones.