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LEED v4.1

Core and Shell

Sustainable Sites
Light Pollution Reduction

LEED CREDIT

CS-v4.1 SSc6: Light Pollution Reduction 1 point

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View the LEED v4 version of this credit »

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Bill Swanson

PE, LEED AP BD+C

Integrated Design Solutions
Sr. Electrical Engineer

SPECIAL REPORT

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Requirements

Meet uplight and light trespass requirements, using either the backlight-uplight-glare (BUG) method (Option 1) or the calculation method (Option 2). Projects may use different options for uplight and light trespass.Meet these requirements for all exterior luminaires located inside the project boundary (except those listed under “Exemptions”), based on the following:

  • the photometric characteristics of each luminaire when mounted in the same orientation and tilt as specified in the project design; and
  • the lighting zone of the project property (at the time construction begins). Classify the project under one lighting zone using the lighting zones definitions provided in the Illuminating Engineering Society and International Dark Sky Association (IES/IDA) Model Lighting Ordinance (MLO) User Guide.
Additionally, meet the internally illuminated signage requirement.
Uplight
Option 1. BUG rating method
Do not exceed the following luminaire uplight ratings, based on the specific light source installed in the luminaire, as defined in IES TM-15-11, Addendum A.
Table 1. maximum uplight ratings for luminaires

MLO lighting zone

Luminaire uplight rating

LZ0

U0

LZ1

U1

LZ2

U2

LZ3

U3

LZ4

U4

OR
Option 2. calculation method
Do not exceed the following percentages of total lumens emitted above horizontal.
Table 2. maximum percentage of total lumens emitted above horizontal, by lighting zone

MLO lighting zone

Maximum allowed percentage of total luminaire lumens emitted above horizontal

LZ0

0%

LZ1

0%

LZ2

1.5%

LZ3

3%

LZ4

6%

AND
Light trespass
Option 1. BUG rating method
Do not exceed the following luminaire backlight and glare ratings (based on the specific light source installed in the luminaire), as defined in IES TM-15-11, Addendum A, based on the mounting location and distance from the lighting boundary.
Table 3. maximum backlight and glare ratings

 

MLO lighting zone

Luminaire mounting

LZ0

LZ1

LZ2

LZ3

LZ4

 

Allowed backlight ratings

> 2 mounting heights from lighting boundary

B1

B3

B4

B5

B5

1 to 2 mounting heights from lighting boundary and properly oriented

B1

B2

B3

B4

B4

0.5 to 1 mounting height to lighting boundary and properly oriented

B0

B1

B2

B3

B3

B0

B0

B0

B1

B2

 

Allowed glare ratings

Building-mounted > 2 mounting heights from any lighting boundary

G0

G1

G2

G3

G4

Building-mounted 1–2 mounting heights from any lighting boundary

G0

G0

G1

G1

G2

Building-mounted 0.5 to 1 mounting heights from any lighting boundary

G0

G0

G0

G1

G1

Building-mounted

G0

G0

G0

G0

G1

All other luminaires

G0

G1

G2

G3

G4

The lighting boundary is located at the property lines of the property, or properties, that the LEED project occupies. The lighting boundary can be modified under the following conditions:
  • When the property line abuts a public area that includes, but is not limited to, a walkway, bikeway, plaza, or parking lot, the lighting boundary may be moved to 5 feet (1.5 meters) beyond the property line.
  • When the property line abuts a public street, alley, or transit corridor, the lighting boundary may be moved to the center line of that street, alley, or corridor.
  • When there are additional properties owned by the same entity that are contiguous to the property, or properties, that the LEED project is within and have the same or higher MLO lighting zone designation as the LEED project, the lighting boundary may be expanded to include those properties.
Orient all luminaires less than two mounting heights from the lighting boundary such that the backlight points toward the nearest lighting boundary line. Building-mounted luminaires with the backlight oriented toward the building are exempt from the backlight rating requirement.
OR
Option 2. calculation method
Do not exceed the following vertical illuminances at the lighting boundary (use the definition of lighting boundary in Option 1). Calculation points may be no more than 5 feet (1.5 meters) apart. Vertical illuminances must be calculated on vertical planes running parallel to the lighting boundary, with the normal to each plane oriented toward the property and perpendicular to the lighting boundary, extending from grade level to 33 feet (10 meters) above the height of the highest luminaire.
Table 4. maximum vertical illuminance at lighting boundary, by lighting zone

MLO lighting zone

Vertical illuminance

LZ0

0.05 fc (0.5 lux)

LZ1

0.05 fc (0.5 lux)

LZ2

0.10 fc (1 lux)

LZ3

0.20 fc (2 lux)

LZ4

0.60 fc (6 lux)

AND

Internally illuminated exterior signage
Do not exceed a luminance of 200 cd/m2 (nits) during nighttime hours and 2000 cd/m2 (nits) during daytime hours.
Exemptions from uplight and light trespass requirements
The following exterior lighting is exempt from the requirements, provided it is controlled separately from the nonexempt lighting:
  • specialized signal, directional, and marker lighting for transportation;
  • lighting that is used solely for façade and landscape lighting in MLO lighting zones 3 and 4, and is automatically turned off from midnight until 6 a.m.;
  • lighting for theatrical purposes for stage, film, and video performances;
  • government-mandated roadway lighting;
  • hospital emergency departments, including associated helipads;
  • lighting for the national flag in MLO lighting zones 2, 3, or 4; and
  • internally illuminated signage.
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Addenda

4/21/2023Updated: 5/9/2023
Reference Guide Correction
Description of change:
Add the following section under Guidance:

"Step-by-Step Guidance
Refer to the LEED v4 reference guide, with the following modification:

 Existing Fixtures
o Calculations must include existing fixtures. If fixture type or manufacturer cannot be identified, the project team should analyze a new, similar fixture with the same bulb type, wattage, lumen output, and physical design that can be expected to have similar photometric properties."
Campus Applicable
No
Internationally Applicable:
No
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Bill Swanson

PE, LEED AP BD+C

Integrated Design Solutions
Sr. Electrical Engineer

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© Copyright U.S. Green Building Council, Inc. All rights reserved.

Requirements

Meet uplight and light trespass requirements, using either the backlight-uplight-glare (BUG) method (Option 1) or the calculation method (Option 2). Projects may use different options for uplight and light trespass.Meet these requirements for all exterior luminaires located inside the project boundary (except those listed under “Exemptions”), based on the following:

  • the photometric characteristics of each luminaire when mounted in the same orientation and tilt as specified in the project design; and
  • the lighting zone of the project property (at the time construction begins). Classify the project under one lighting zone using the lighting zones definitions provided in the Illuminating Engineering Society and International Dark Sky Association (IES/IDA) Model Lighting Ordinance (MLO) User Guide.
Additionally, meet the internally illuminated signage requirement.
Uplight
Option 1. BUG rating method
Do not exceed the following luminaire uplight ratings, based on the specific light source installed in the luminaire, as defined in IES TM-15-11, Addendum A.
Table 1. maximum uplight ratings for luminaires

MLO lighting zone

Luminaire uplight rating

LZ0

U0

LZ1

U1

LZ2

U2

LZ3

U3

LZ4

U4

OR
Option 2. calculation method
Do not exceed the following percentages of total lumens emitted above horizontal.
Table 2. maximum percentage of total lumens emitted above horizontal, by lighting zone

MLO lighting zone

Maximum allowed percentage of total luminaire lumens emitted above horizontal

LZ0

0%

LZ1

0%

LZ2

1.5%

LZ3

3%

LZ4

6%

AND
Light trespass
Option 1. BUG rating method
Do not exceed the following luminaire backlight and glare ratings (based on the specific light source installed in the luminaire), as defined in IES TM-15-11, Addendum A, based on the mounting location and distance from the lighting boundary.
Table 3. maximum backlight and glare ratings

 

MLO lighting zone

Luminaire mounting

LZ0

LZ1

LZ2

LZ3

LZ4

 

Allowed backlight ratings

> 2 mounting heights from lighting boundary

B1

B3

B4

B5

B5

1 to 2 mounting heights from lighting boundary and properly oriented

B1

B2

B3

B4

B4

0.5 to 1 mounting height to lighting boundary and properly oriented

B0

B1

B2

B3

B3

B0

B0

B0

B1

B2

 

Allowed glare ratings

Building-mounted > 2 mounting heights from any lighting boundary

G0

G1

G2

G3

G4

Building-mounted 1–2 mounting heights from any lighting boundary

G0

G0

G1

G1

G2

Building-mounted 0.5 to 1 mounting heights from any lighting boundary

G0

G0

G0

G1

G1

Building-mounted

G0

G0

G0

G0

G1

All other luminaires

G0

G1

G2

G3

G4

The lighting boundary is located at the property lines of the property, or properties, that the LEED project occupies. The lighting boundary can be modified under the following conditions:
  • When the property line abuts a public area that includes, but is not limited to, a walkway, bikeway, plaza, or parking lot, the lighting boundary may be moved to 5 feet (1.5 meters) beyond the property line.
  • When the property line abuts a public street, alley, or transit corridor, the lighting boundary may be moved to the center line of that street, alley, or corridor.
  • When there are additional properties owned by the same entity that are contiguous to the property, or properties, that the LEED project is within and have the same or higher MLO lighting zone designation as the LEED project, the lighting boundary may be expanded to include those properties.
Orient all luminaires less than two mounting heights from the lighting boundary such that the backlight points toward the nearest lighting boundary line. Building-mounted luminaires with the backlight oriented toward the building are exempt from the backlight rating requirement.
OR
Option 2. calculation method
Do not exceed the following vertical illuminances at the lighting boundary (use the definition of lighting boundary in Option 1). Calculation points may be no more than 5 feet (1.5 meters) apart. Vertical illuminances must be calculated on vertical planes running parallel to the lighting boundary, with the normal to each plane oriented toward the property and perpendicular to the lighting boundary, extending from grade level to 33 feet (10 meters) above the height of the highest luminaire.
Table 4. maximum vertical illuminance at lighting boundary, by lighting zone

MLO lighting zone

Vertical illuminance

LZ0

0.05 fc (0.5 lux)

LZ1

0.05 fc (0.5 lux)

LZ2

0.10 fc (1 lux)

LZ3

0.20 fc (2 lux)

LZ4

0.60 fc (6 lux)

AND

Internally illuminated exterior signage
Do not exceed a luminance of 200 cd/m2 (nits) during nighttime hours and 2000 cd/m2 (nits) during daytime hours.
Exemptions from uplight and light trespass requirements
The following exterior lighting is exempt from the requirements, provided it is controlled separately from the nonexempt lighting:
  • specialized signal, directional, and marker lighting for transportation;
  • lighting that is used solely for façade and landscape lighting in MLO lighting zones 3 and 4, and is automatically turned off from midnight until 6 a.m.;
  • lighting for theatrical purposes for stage, film, and video performances;
  • government-mandated roadway lighting;
  • hospital emergency departments, including associated helipads;
  • lighting for the national flag in MLO lighting zones 2, 3, or 4; and
  • internally illuminated signage.

LEEDuser expert

Bill Swanson

PE, LEED AP BD+C

Integrated Design Solutions
Sr. Electrical Engineer

See all LEEDuser forum discussions about this credit » Subscribe to new discussions about CS-v4.1 SSc6