A classification of outdoor luminaires by the lumens they emit in angular zones: B for backlight behind the pole, U for uplight above horizontal, and G for glare at high forward angles. Each gets a number from 0, best, to 5, as in B1-U0-G1. Lighting ordinances and dark-sky guidance set maximum BUG values by lighting zone, and the rating is calculated from the luminaire's IES file.
Pole at the property line needs a house-side shield, the plain type 3 has a BUG rating of B3 and the limit there is B1.
Also heard as
- BUG
- backlight uplight glare
- B-U-G
Related terms
Cutoff
The angle above which a luminaire emits little or no light, used to classify glare and light pollution control.
Light trespass
Unwanted light that crosses a property line or falls where it is not needed, such as into a neighbor's window.
IES file
A standard text file of a luminaire's measured candela distribution, loaded into lighting calculation software.
Glare
Visual discomfort or loss of visibility caused by excessive brightness or contrast in the field of view.