Dimming the Night Sky

After the Soviet Sputnik satellite streaked across the night sky in 1957, star gazing became a popular hobby. But like other natural resources, our sky has become polluted. In nearly every major U.S. city, stars and satellites are becoming less visible. Researchers predict that by 2025, no dark skies will remain in the continental United States.

The International Dark-Sky Association (IDA) estimates 30 percent of commercial, industrial, residential and transportation lighting is wasted. Energy waste can result from leaving unneeded lights on, overlighting, installing high-glare fixtures, lighting directly into the sky, and building new homes with indoor and outdoor incandescent lighting. Approximately 110 billion kilowatt-hours (kWh) a year are wasted in the United States because of ill-conceived, ineffective or inefficient lighting.

Moreover, light pollution can disrupt circadian rhythms and sleep patterns. Environmental effects include increased energy consumption and disruptions of local ecosystems, which impacts migratory birds, sea turtles, insect populations and other species.

As the green movement grows, more building owners are considering the impact of light pollution on their brands and reputations. For example, building occupants and communities are paying more attention to the “lights are on, nobody’s home” syndrome because it communicates the owner is not concerned about the environment.

With the rise of eco-tourism, hotels and resorts are promoting themselves as “sustainable destinations” and are recognizing dark skies enhance the experience of guests, especially for resorts in natural settings.

Almost 20 years ago, the Tucson-based IDA spearheaded preserving the endangered night sky. Thousands of local ordinances have been enacted nationwide. Most of the legislation emphasizes lighting fixtures restricting light directed up, according to Mark Lien, a LEED-accredited professional and the director of the Lighting Solutions Center, Hubbell Lighting Inc., Greenville, S.C.

“Some laws limit wattage, lamp types, the times streetlights must be reduced to 50 percent power, or times sports lighting must be turned off.”

According to Lien, astronomers and sky-gazers initially were more active in this issue than the lighting industry, resulting in some well-intended wording becoming problematic. “Stipulating existing fixtures be replaced without provision for who should pay for the change, inconsistent light distribution definitions, product types and unachievable requirements negatively impacted IDA’s perception among lighting professionals. But that has changed, and the IDA has supporters from both camps,” Lien said.

Most current light pollution legislation stipulates “full cut-off” type fixtures, which, according to the Illuminating Engineers Society (IES) definition, means no light can be directed upward. The intent is limiting the uplight controls. When light is directed up at night, it reflects and refracts off dust, moisture and smog—creating a visual barrier to seeing stars. The so-called “skyglow” prevents seeing the night sky.

Terminology is changing, Lien said. “The terms full cut-off, semi-cut-off and non-cut-off are fading away. They were not intended to be used to address light pollution. A new system is being embraced by both the IDA and the IES. The new term is the ‘BUG’ rating system [B for backlight, U for uplight and G for glare].”

The IES and IDA are collaborating on a Model Lighting Ordinance (MLO) for municipalities to use in developing and implementing regulations to prevent offensive outdoor lighting.

Lien said the MLO recommends lighting only “where and when needed to prevent or mitigate adverse offsite impacts, protect and preserve the nighttime environment, and promote safety for the welfare of the community.”

Lighting efficiency sometimes suffered when the full cut-off fixtures were mandated, Lien said.

“If light distribution is narrow and focused only downward, additional fixtures may be needed to maintain acceptable uniformity ratios. The IES recommends light levels and uniformity ratios for outdoor applications,” he said.

Both are important. “If outdoor levels are not acceptably uniform, our eyes cannot adapt quickly enough, which can cause safety and security issues. In some applications, the additional fixtures needed to achieve acceptable uniformity use more electricity. Focusing all light downward also can cause more light to reflect up—defeating the legislation’s intent,” Lien said.

The increased design flexibility of BUG rating allows lighting designers to mix fixture types if they maintain skyglow control, according to Lien. This flexibility enables using some wider distribution fixtures for a balanced approach.

Light pollution, urban sky glow, light trespass and glare all are outdoor lighting concerns legislation targets. These issues are relative to the lighting installation area. Because a rural area has no competing light sources, a small amount can be adequate. Light is cumulative, so bright city areas may need higher light levels.

A system identifying these areas and setting varying standards has been developed and is part of IES exterior lighting recommendations as well as the new MLO, Lien said. These lighting zones will be an aspect of future legislation.

The zone system is used in existing ordinances to limit pole or fixture mounting height, lamp wattages and optical distribution, Lien said. Zone 0 or 1 will have the most restrictions where little or no light is needed. Zone 2 will allow more light, similar to a rural area. Zone 3 will be the brightest identified, such as in a large downtown district. Zone 4 provides exceptions for theme parks, Times Square, the Las Vegas Strip, high-crime areas or wherever the zoning board acknowledges a special need.

Exterior lighting can look brighter without using additional energy with a white light source, such as metal halide, rather than high-pressure sodium, which emits a yellowish light.

“In very bright light, our eyes are most sensitive to the warm or yellow light sources, but at low or night light levels our eyes perceive that cooler color temperatures like metal halide appear brighter,” Lien said. “In empirical studies, the foot-candle measurement of metal halide light often appears twice as bright as high-pressure sodium at night. In addition, research has shown we have increased depth of field with the white light sources. Thus, objects appear clearer at a distance, which increases our perception of brightness.”

Energy conservation will influence future legislation. Skyrocketing utility costs and power generation environmental concerns will force fixture design market shifts. Higher quality reflectors, more precise refractors, high-wattage electronic ballasts and maximum energy efficiency optical control will be worth the premium cost, Lien said.

As energy costs increase, return on investment is quicker, and the reduced electricity consumption lessens the environmental impact from nitrogen, sodium and carbon emissions produced by power plants. Wattage limitations for exterior applications are included in ASHRAE 90.1-2004 legislation as well as in many state and local ordinances.

Light pollution relates to the growing awareness of sustainability and green issues among architects and building owners. All things being equal, most owners prefer buildings that are good for the community and good for the environment. Since controlling light pollution actually saves money for owners by reducing energy consumption, everybody wins.

EC opportunities

Building owners find public relations value in addressing light pollution and communicating that fact to occupants, visitors, customers and neighbors.

Still, why aren’t building owners doing more to address light pollution? The main reason is probably lack of attention to the issue, said Eric Lind, commercial marketing director at Lutron Electronics Co. Inc., Coopersburg, Pa.

“The opportunity for electrical contractors is to proactively raise the issue with customers. Once the building owner/facility manager focuses on the issue, electrical contractors can offer a variety of cost-effective ideas, generating incremental business and creating another point of contact with the customer and strengthening the customer relationship,” Lind said.

Existing systems can be easily retrofitted to reduce light pollution (while at the same time saving energy and helping to meet energy codes), Lind said, adding that: “In new construction, light pollution strategies can be implemented through intelligent lighting systems such as Lutron’s EcoSystem solution. ECs can look to manufacturers as well as distributors for help in implementing these solutions.”

Lind points out some key solutions for ECs to consider:

  • An astronomical time clock to turn off non-essential lights at night
  • Occupancy sensors to turn off lights in areas not occupied
  • Dimmable ballasts (for example, linked to the time clock) to keep lights at a low level for security purposes while dramatically reducing light pollution and energy consumption at night
  • Shading systems to block or reduce light from escaping the building at night. The same systems that are used to reduce daytime glare can help reduce nighttime light pollution.
  • Control systems enabling the building owner/facility manager to integrate and automate these functions
  • Buildings can earn one point of LEED certification for reducing light pollution.

To address concern over the ever-increasing amount of unregulated spill light created by roadway and parking lot lighting, manufacturers are offering solutions.

For instance, Cooper Lighting offers the SLE reflector options for its luminaires. The SLE reflector system strictly controls spill light, maintains IES full cut-off classification and provides exceptional forward throw performance. The SLE is not a house-side shield, but rather a new precision-engineered optical system maximizing useful forward illumination while carefully redirecting and shielding light that normally travels behind the pole.

With manufacturer solutions and activism, the dark-sky movement will likely be effective. “The good news is we can rediscover what we lost,” Lien said. “Everything we need is available to design attractive and efficient lighting systems. The light can be directed just where it is useful instead of upward, again revealing the stunning beauty of the night sky.”

For additional recommendations on exterior lighting requirements, see www.iesna.org for RP33-99 Lighting for Exterior Environments and G-1-03 Guideline on Security Lighting for People, Property, and Public Spaces. For dark-sky issues and access to local and state ordinances, see www.darksky.org. EC

WOODS writes for many consumer and trade publications. She can be reached at patwoods123@hotmail.com.

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