METAL HALIDE EXAMPLE OF BUG RATINGS

Addendum A for IES TM-15-11: Backlight, Uplight, and Glare (BUG) Ratings

This Addendum replaces Addendum A in IESNA TM-15-07.
The following Backlight, Uplight, and Glare ratings may be used to evaluate luminaire optical performance related to light trespass, sky glow, and high angle brightness control. These ratings are based on a zonal lumen calculations for secondary solid angles defined in TM-15-11. The zonal lumen thresholds listed in the following three tables are based on data from photometric testing procedures approved by the Illuminating Engineering Society for outdoor luminaires (LM-31 or LM-35).

How is a BUG Rating of LED Parking Lot Lights Calculated?

A: Light fixtures calculate lumens, light direction and colors by going into a round sphere called an integrating sphere. This sphere fully encloses a fixture allowing for the light to be measured at every point in a 360 degree fashion. The sphere enables exact measurements of lumens regardless of the directionality of the fixture. The resulting file can be used to model up light installations for planning, permitting and other functions.

Table A-1: Backlight Ratings (maximum zonal lumens)
Backlight Rating
Secondary Solid Angle B0 B1 B2 B3 B4 B5

Backlight
Trespass

 BH 110 500 1000 2500 5000 >5000
BM 220 1000 2500 5000 8500 >8500
BL 110 500 1000 2500 5000 >5000
Table A-2: Uplight Ratings (maximum zonal lumens)
Uplight Rating
Secondary Solid Angle U0 U1 U2 U3 U4 U5

Uplight
Skyglow

 UH 0 10 50 500 1000 >1000
UL 0 10 50 500 100 >1000

Table A-3: Glare Ratings (maximum zonal lumens)
Glare Rating for Asymmetrical Luminaire Types (Type I, II, III, IV)
Secondary Solid Angle G0 G1 G2 G3 G4 G5

Glare
Offensive Light

 FVH 10 100 225 500 750 >750
BVH 10 100 225 500 750 >750
FH 660 1800 5000 7500 12000 >12000
BH 110 500 1000 2500 5000 >5000
Glare Rating for Quadrilateral Symmetrical Luminaire Types (Type V, V Square)
Secondary Solid Angle G0 G1 G2 G3 G4 G5

Glare
Offensive Light

 FVH 10 100 225 500 750 >750
BVH 10 100 225 500 750 >750
FH 660 1800 5000 7500 12000 >12000
BH 110 500 1000 2500 5000 >5000

"BUG" Rating Example:

A 250-watt MH area luminaire, Type IV forward throw optical distribution.
Based on the photometric test data, the luminaire has the following zonal lumen distribution:

FORWARD LIGHT LUMENS % LAMP LUMENS
FL (0° - 30°) 1618 5.9%
FM (30° - 60°) 6093 22.2%
FH (60° - 80°) 3748 13.6%
FVH (80° - 90°) 27 0.1%
BACKLIGHT LUMENS % LAMP LUMENS
BL (0° - 30°) 985 3.6%
BM (30° - 60°) 930 3.4%
BH (60° - 80°) 136 0.5%
BVH (80° - 90°) 16 0.1%
UPLIGHT LUMENS % LAMP LUMENS
UL (90° - 100°) 0 0.0%
UH (100° - 180°) 0 0.0%
Backlight Rating:

Determine the lowest rating where the lumens for all of the secondary solid angles do not exceed the threshold lumens from Table A-1. In this example the backlight rating would be B2 based on the BL lumen limit.

Uplight Rating:

Determine the lowest rating where the lumens for all of the secondary solid angles do not exceed the threshold lumens from Table A-2. In this example the uplight rating would be U0 based on the UL and UH lumen limits.

Glare Rating:

Determine the lowest rating where the lumens for all of the secondary solid angles do not exceed the threshold lumens from Table A-3 for a Type IV distribution. In this example, the glare rating would be G2 based on the FH lumen limit. Therefore, the BUG rating for this luminaire would be: B2 U0 G2