Is Your LEED Building Project Contributing to Light Pollution?

Kristen Sharp's picture
Kristen Sharp
October 11, 2016

Learn how to re-illuminate the night sky with LEED’s helpful suggestions for reducing light pollution.

LEED mandates that we keep the night sky dark.
LEED mandates that we keep the night sky dark.

A common thread seems to connect various ecosystems: light pollution.

Combining the populations of the United States and Europe, a mere one percent can see the night sky in all its beauty. A staggering 80 percent of the world resides under skyglow and are robbed of any natural nightlight.

Skyglow is the overwhelming luminance that radiates from a city full of lights. Electric man-made lighting contributes significantly to this problem, as do naturally occurring weather conditions. Primarily, it affects the naked eye’s ability to see stars. 

Skyglow is just one of many terms used to describe instances of light pollution.

Light pollution -- the misuse or overuse of light -- has been proven to be detrimental to humans, animals and the environment. Common manifestations of light pollution include glare, skyglow, light trespass, and clutter.

Glare occurs when too much light is present and a cluster forms that is too uncomfortable to see past. A perfect comparison is the overwhelming amount of light that is created when cars in opposite lanes both have on their high beams. The excessive amount of light results in a glare that makes it difficult to see the road and drive safely.

 Light trespass -  or careless lighting installation that shines light in unwanted areas - and clutter, which refers to excessive, bright and disorienting lighting, are both technical terms for light pollution.  Having become accustomed to poorly or haphazardly designed lights, we fail to recognize their negative effects.

Fortunately, light pollution awareness has increased in addition to emerging solutions for pollution reduction. Meticulous light installation is but a small step towards a less polluted cityscape.

LEED’s Sustainable Sites Light Pollution Reduction Credit provides guidance for bringing back the night sky.

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Light Pollution Reduction Credit Requirements

LEED’s Light Pollution Reduction credit is worth one point and asks that the building project choose between the calculation or the BUG (backlight-uplight-glare) method to satisfy uplight and light trespass requirements.

To explain the BUG method and other requirements in greater detail, LEED enlists the help of the Illuminating Engineering Society (IES) and the International Dark-Sky Association (IDA).

In fact, both organizations have partnered together to create the Model Lighting Ordinance (MLO), which “will allow communities to drastically reduce light pollution and glare and lower excessive light levels.” The MLO defines the  five IDA-recommended lighting zones

●     LZ0: No ambient lighting. LZ0 areas should remain as naturally dark as possible.

●     LZ1: Low ambient lighting. In LZ1 areas, occupants have adapted to lower lighting. This lighting zone is used for safety and security. However, as human activity declines, so should the lighting.

NOTE: The following lighting zones increase in brightness, but follow the same guidelines as LZ1. As activities decrease, so should the artificial lighting, in an effort to preserve as much of the night sky as possible.

●     LZ2: Moderate ambient lighting

●     LZ3: Moderately high ambient lighting

●     LZ4: High ambient lighting

BUG Method

The BUG (backlight-uplight-glare) method determines a light fixture’s probability of producing light pollution. Project managers should use the BUG ratings to gauge exactly how their light fixtures will perform in relation to metrics of light pollution-- including light trespass, skyglow or high angle brightness control. Find all the ratings for backlight, uplight and glare in the Illuminating Engineering Society’s addendum.

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Calculation Method

The calculation method requires that project teams do not exceed the following vertical illuminances at each lighting boundary, or the perimeter of each lighting zone within the project border line.

Note: Calculation points can be a maximum of 5 feet (1.5 meters) apart. For more details on how the calculation method works, consult the LEED v4 for Neighborhood Development.

Exterior Requirements

●     The light measurement characteristics of each luminaire when placed in the same position and sitting in the same manner that is described in the project design.

●     The lighting zone of the project property (at the time construction begins). Select a lighting zone that best explains the building project’s lighting situation as defined by the MLO User Guide. Classify the project under one lighting zone.

For indoor signs that illuminate outside, the luminance cannot exceed 200 cd/m2 (nits) during nighttime hours and 2000 cd/m2 (nits) during daytime hours.

Some outdoor lighting classifies as an exception and does not have to fulfill the credit requirements, as long as it is separate from all nonexempt lighting. For specifics on what type of lighting is exempt, consult the LEED BD+C reference guide.

LEED recommends that project teams adhere to these guidelines because prolonged exposure to light pollution can adversely affect building occupants, as well as local wildlife.

Light Pollution and Humans

We need our nights to be dark and our days to be light. We risk disrupting more than just our circadian rhythm after prolonged exposure to artificial lighting before sleep. WikipediaOverexposure to artificial lights has been linked to cancer, obesity, diabetes and cardiovascular disease. Blue lights -- such as lights from computers, TVs or LEDs -- are especially problematic. White LEDs, the high-intensity, blue-rich technology operating most U.S. roadways, were recently denounced by the American Medical Association and proven to exacerbate the health risks associated with light pollution.    

Project managers should opt for a less harsh, low-color temperature light source. Making this switch in lighting fixtures proves to be a viable strategy for reducing the risk of light pollution. Purchase low-impact lights not exceeding 3500 degrees Kelvin, keeping in mind the overall well being of building occupants. The ultimate solution is to become informed on our current lighting systems, and the extent to which they impact human health and local ecosystems.

Light Pollution and Wildlife

For nocturnal animals, light pollution is a matter of life or death. Sea turtles, for example, rely on natural light for navigation. While sea turtles predominantly reside in the ocean, they travel to the beach under the moonlight to hatch their eggs.

Hatchlings must use the natural light radiating from the sun rising over the ocean to navigate back to the sea. Artificial lights disorient baby sea turtles and lead them astray. As a result, light pollution kills millions of hatchlings in Florida annually.

Similarly, nocturnal birds depend on natural light from the stars and moon to illuminate their surroundings. When artificial light disrupts their nocturnal field of vision, the birds are so disoriented that, often times, they lose their flight path permanently, Unfortunately, millions of birds lose their lives yearly because of the overabundance of light from buildings.

Migrational birds base their travel plans on cyclical light patterns as well, attuning their routes to seasonal shifts.They can easily mistake artificial lights for natural cues, which could lead to either a premature or delayed migration.  Any slight misdirection could cost them the opportunity to travel during ideal climates for nesting, foraging and other biotic processes.

Luckily, pursuing safer lighting solutions is only one of many alternatives available to today’s building project teams. Before choosing any fixture, project teams should consider the effects of lighting designs on occupant health, wildlife, and pollution.

As light pollution continues to remain a common thread that influences the built environment, it is important that teams implement LEED strategies which could significantly mitigate this problem.

For more information on how to reduce light pollution, check out the International Dark-Sky Association (IDA). IDA is “the recognized authority on light pollution and is the leading organization combating light pollution worldwide.” IDA’s mission is to preserve the night sky and also educate the public on ways to decrease light pollution worldwide.

Be a part of the solution by becoming a member of or donating to IDA today.



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