Light Pollution: Issues, Guidance and 3dOP
By Craig DiLouie
Most lighting professionals are aware that light pollution obscures night-time viewing of stars and interferes with astronomical observations, but it’s also an energy, environmental and community issue. An estimated 30 percent of energy used for outdoor lighting ends up flying into outer space-some $1.5 billion a year, according to a study conducted by the International Dark Sky Association. In addition, an estimated 100 million birds die each year from flying into buildings and other man-made structures due to light pollution. And light trespassing from one property onto others, particularly glare, has resulted in a need for recourse among homeowners.
As indicated, while the term “light pollution” is often attributed with sky glow, it is often considered to have three components: sky glow (light emitted up into the sky, which can obscure night-time viewing of stars and interfere with astronomical observations), glare (brightness that impairs or disables vision), and light trespass (light emitted into neighboring property).
These issues have united astronomers, environmentalists and communities to adopt light pollution legislation in a large number of states and municipalities across the United States. These issues are also lighting design issues, of course. Lighting practitioners engaged in developing outdoor lighting designs, already sensitive to glare and light trespass issues, are now increasingly being required to accommodate requirements that address skyglow.
The 2005-2006 Light Pollution Study, conducted by ZING Communications, Inc. and based on surveys distributed to 2,847 industry participants with a 6.9 percent response, suggests that architects, lighting designers and engineers are by and large aware and informed about light pollution issues, and that they consider light pollution prevention to be good lighting design. The research suggests that lighting practitioners consider glare to be most important as a light pollution issue, followed by light trespass and then sky glow.
Below are two examples of how light pollution issues are addressed in the industry:
LEED Rating System
The U.S. Green Building Council’s Leadership in Energy & Environmental Design (LEED) has become a driving force behind the sustainable design movement. LEED provides a rating system through which buildings can earn points to receive LEED certification. Addressing light pollution is recognized by LEED as a sustainable measure.
Sustainable Sites represents 22 percent of the total possible LEED points and intersects with lighting in Credit 8, Light Pollution Reduction (1 point). LEED requires the architect to “eliminate light trespass from the building and site, improve night sky access and reduce development impact on nocturnal environments.”
To gain this point, the lighting practitioner must:
- meet or provide lower outdoor light levels than those recommended by IESNA RP-33-99: Lighting for Exterior Environments
- ensure that the maximum candela value for all indoor lighting must fall within the building (not through the windows)
- ensure that the maximum candela value for all outdoor lighting must fall within the property
- specify shielding for any fixture within a distance of 2.5 times its mounting height from the property boundary, so that no light spills over the boundary.
In addition, all fixtures that produce more than 1,000 initial lumens must be shielded, and all fixtures that produce more than 3,500 initial lumens must meet the Full Cutoff IES classification so no light is emitted skyward.
California 2005 Title 24 Energy Code
California has what many consider the strictest energy code in the country-The Energy Efficiency Standards for Residential and Nonresidential Buildings, Title 24, Part 6, of the California Code of Regulations. The state recently updated Title 24 with a new 2005 version designed to respond to legislation and the recent energy crunch. The 2005 code changes supersede the 2001 standards. Projects that apply for a building permit must comply with the 2005 standards.
Some of the most significant lighting changes to Title 24 for non-residential buildings include new provisions for outdoor lighting.
The provisions establish lighting zones (1-4) and set power limits per zone according to how much light is needed (rural areas, urban areas, highly lit areas, etc.). Lighting Zone 1 (parks, recreation areas, wildlife preserves) is designated as “dark”; Lighting Zone 2 (rural areas) is designated for low ambient illumination; Lighting Zone 3 (urban areas) is designated for medium ambient illumination; and Lighting Zone 4 is designed for high ambient illumination.
In addition, Title 24’s outdoor lighting provisions require all fixtures going into hardscape areas, e.g. parking lots with lamps greater than 175W, need to be at least IES cutoff classified. Exceptions include some sign lighting, lighting on building facades, statues, monuments, vertical bridge lighting, emergency lighting, temporary lighting, and areas subject to Article 680, CA Electric Code.
Also all permanently installed outdoor luminaries with greater than 100W lamps must have a lamps efficacy of at least 60 lumens per watt or be controlled by a motion sensor. The code defines efficacy to be initial lumens divided by input watts. In addition, all fixtures must be controlled by a photocell or time switch when daylight is available.
Evolution of Guidelines
Despite these types of guidelines, there remains some confusion in the industry about how to implement them and what solutions work best.
For example, the current cutoff classification system, originally developed for roadway lighting applications in the early 1960s, does not meet today’s needs for increased control of glare, says Michele McColgan, PhD, the Lighting Research Center’s (LRC’s) outdoor lighting expert. “The current system is ineffective in determining luminaire performance for general outdoor applications,” she says. In addition, according to the LRC, some manufacturers have created their own classifications to promote the unique characteristics of their products-some of which have been accepted unofficially by the lighting industry, although they are not recognized by IESNA.
As a result, IESNA has requested that the LRC prepare a new, proposed classification system for outdoor fixtures. The new system redefines light distributions for fixtures used in parking lots, roadways and other outdoor areas. The IESNA’s Board of Directors is currently reviewing the proposed system.
“I believe that manufacturers are just waking up to the issues,” says Ian Ibbitson, VP/General Manager for ALLSCAPE, a manufacturer of outdoor pedestrian-level and landscape lighting. “Some have already provided full cutoff solutions, but there is room for considerable improvement. Over the next five years, we will see much more activity.”
Ibbitson believes the industry has been slow to take the lead on light pollution and has been driven by outside influences. It is now in the process of catching up, developing guidelines and creating balanced and scientific views, he says.
Light Pollution Legislation
Not only do lighting practitioners need guidelines, but so do governments that are trying to address light pollution issues through legislation. The ZING Light Pollution Study suggests that a significant number of lighting designers, architects and engineers are required to comply with state or local laws that regulate light pollution in both commercial and residential areas.
States that have adopted legislation with provisions that address at least one or more light pollution issues include California (SBX15), New Mexico (Night Sky Protection Act), New Jersey (27:5-9c dealing with signage lighting), Rhode Island (Chapter 420 2002-S 2399A), Connecticut (Connecticut Public Act of 01-134), Arizona (Title 49, chapter 7, light pollution statutes), Texas (HB 916), Maine (5 MRS 1769), Colorado (HB-01-1160) and Georgia (HB 942 and HB 645). States with pending legislation include Maryland, Wyoming, Iowa, Michigan, Virginia, Delaware, Pennsylvania, New York, New Hampshire and Massachusetts. In other states, ordinances controlling outdoor lighting may be in effect at the local level and a number of national parks have adopted their own initiatives.
Behind much of the legislation is the International Dark Sky Association (IDA), formed in 1988. IDA’s mission, as it says on the association’s web site www.darksky.org, is to stop “the adverse environmental impact on dark skies by building awareness of the problem of light pollution and of the solutions, and to educate everyone about the value and effectiveness of quality nighttime lighting.” The association now has more than 10,000 members from all states in the U.S., most provinces of Canada and from more than 70 other countries. Since 1990, IDA has been instrumental in helping to pass over 1,000 lighting laws controlling outdoor lighting and is now working on a national standard outdoor lighting code to help communities pass ordinances that are consistent.
A standard outdoor lighting code or model ordinance appears to be direly needed. The ZING Light Pollution Study suggests that lighting practitioners more often than not find light pollution laws easy to understand, but often do not find them easy to implement, and across municipalities, the designer must often learn and accommodate many types of laws.
More often than not, lighting practitioners do not consider light pollution laws to restrict their ability to design cost-effective, safe and visually pleasing outdoor lighting solutions-if only the laws themselves were clear and based on industry guidelines, according to the Study.
One designer responding to the Study survey noted, “Manufacturers should meet with city officials and help to educate them on the issues and encourage them to hire a qualified lighting designer to help them write ordinances. Typically, ordinances are completely non-sensical with ‘foot-candela’ requirements (no kidding, I ran into this), obviously written by people who don’t understand lighting.”
Says Ibbitson: “It must be a nightmare for lighting designers to cope with the plethora of city codes and ordinances growing on a daily basis, much of which is driven by local activists and not by lighting professionals. These tend to be random, often ambiguous and poorly enforced. For example, light levels and uniformity criteria are often included but not defined.”
Help may be on the way. IESNA recently began developing its own model ordinance, which can be adopted by municipalities to address light pollution in their own communities in a practical manner that reflects lighting industry guidelines. If this occurs, it would be a considerable development, as lighting people would be driving the development of model legislation, not astronomers.
Despite the continuing light pollution legislative wave, Ibbitson believes energy-based legislation will ultimately drive manufacturers more than dark sky issues. “Hopefully, the savviest manufacturers will provide fixtures that will be optimal from both sides,” he says.
Looking for the Right Solution
Possibly the biggest debate, however, will be over what solutions are most practical for addressing light pollution problems, and by what metrics they should be compared and judged. The first thing to understand, says Ibbitson, is that there is no panacea.
“Lighting is as much an art as a science,” he says. “A good lighting designer understands the issues and how complex they can be. Non-professionals believe that full cutoff and house-side shields solve all the issues.”
What is missing, says Ibbitson, is a single, clear set of guidelines and standardized metrics for fixture and design evaluation and comparison.
“There are really no standardized metrics or tools that evaluate competing designs with regard to glare, light trespass and sky glow,” he notes.
For example, the ZING Light Pollution Study revealed that a significant number of design professionals would like to see standardized labeling of light fixtures to show compliance of maximum wattage (or lumens) for different lighting zones.
The Study suggests that fixture positioning, full cutoff fixtures, shielded parking lot or area lighting fixtures, shielded building-mounted fixtures, fully shielded fixtures, and house-side shields or external shielding for fixtures are popular strategies for addressing light pollution. While there is no single ideal solution, “The bottom line is that fixtures that convert more electricity to light in a controlled and predictable way will be the successful ones in the future,” says Ibbitson.
Full cutoff fixtures, for example, have become associated with best practice regarding light pollution prevention. With no light emitted upward and little output in the currently accepted “glare zone,” they appear to be an ideal solution. However, there has been some debate about the utility of full cutoff fixtures for two reasons. First, a portion of light directed at the ground is still emitted into the night sky, particularly when the ground is represented by light-colored surfaces, and more fixtures and/or higher-wattage lamps may be required to achieve the desired lighting effect. In the ZING Light Pollution Study, more than one-half of lighting designer and engineer respondents believe full cutoff fixtures are a “questionable solution” for these reasons.
“Solutions such as full cutoff fixtures, combined with shorter poles to prevent light trespass, may result in a less environmentally friendly solution,” notes Ibbitson. Some solutions reduce light pollution, but require more energy consumption, while others that appear optimal from both sides, such as low pressure sodium lamps, often do not provide the best lighting solution.
Questions to Ask
Ibbitson believes that lighting practitioners should always address five basic questions when starting an outdoor lighting project:
- What codes, ordinances or job-specific requirements are there?
- What’s on the other side of the job perimeter? (What is the general ambient light level in the general vicinity of the job? Are there residential areas on the boundary where light trespass will be a concern?) “The perimeter also includes towards the sky,” says Ibbitson. “Is there is a local observatory, air flight paths or local codes that prohibit or limit light levels above a certain height?”
- What is the energy budget for the job? (Are there limitations on power that can be provided?) “This is needed as a limited power budget may be at odds with using full cutoff fixtures everywhere,” notes Ibbitson.
- What are the owner’s lighting expectations? (Does he or she want the building to stand out, or do they want a subtle lighting job? Do they have any environmental beliefs that should be taken into account?) “You should always know what the person paying you thinks,” says Ibbitson. “As an example, what is the owner’s tolerance to lighting tradeoffs? Less light and glare may result in a less uniform lighting solution and possibly security or cost concerns.”
- What are the job specific issues? Is the building made of glass? Can the building be designed with features where the lights can be hidden? Etc.
Guidance
Keeping in mind that there are no cure-alls for light pollution and that every lighting project is different, general principles that can be used to address light pollution are shown below:
1) Select outdoor lighting fixtures with optics and/or shielding that enables maximum “cut-off” appropriate for the light source so as to strictly control the direction and pattern of light and eliminate spill light.
(In review, “Cut-off” refers to the proportion of light output of a fixture being distributed at 80 and 90 degrees above nadir, this being 0 degrees, a line pointing straight downward. Full cut-off fixtures distribute no light output at 90 degrees above nadir and less than 10 percent at 80 degrees above nadir. In other words, the light is directed downward in a controlled pattern.)
The result is less glare. “When visual environment lighting is the measurement, then the installations are similar in initial costs,” said Nancy Clanton, PE, IALD, LC, president of Clanton & Associates, Inc. of Boulder, CO, in an article about light pollution published in TED Magazine. “Some argue that you need more equipment with fully shielded luminaires. These arguments are weak because they equate light levels and uniformities only. They do not take into account increased visibility when glare is reduced.”
Ibbitson cautions that designers take into account how the fixture interacts with the site that in turn can offer sources of glare and skyglow: “Be aware of the site and possible reflective surfaces,” he says.
2) Select fixtures for billboards that light the sign downward rather than upward.
3) Do not overlight the space. Determine the project lighting zone and select light levels that are right for that zone. Look beyond the footcandle as the sole design criterion for outdoor lighting and be sensitive to, and address, the glare impact of different types of lighting equipment. Brighter lights do not necessarily mean better visibility.
“Always avoid glare if possible,” says Ibbitson. “Know where the people are and make sure that the fixtures are placed to minimize any direct lighting effects. Look at the vertical light levels in areas where glare could be an issue and try to minimize. A good thoughtful design usually makes all the difference.”
3) Keep the aiming angles of floodlighting low so the light does not stray from its intended target. Some experts recommend externally and internally shielded floodlighting only for carefully designed sports complexes due to the glare that is often associated with floodlighting installations.
4) Consider higher mounting heights for floodlighting fixtures, which provides the ability to keep the aiming angle low and select narrower beam light distributions.
5) Be thoughtful of light pollution issues and address them during the design phase by being aware of all the environmental factors at the job site. Light only the areas that require it; there are often areas that should not be lighted.
6) Use controls to turn off or dim light levels based on the use of the space. During the early morning hours, many types of lighting, such as landscape lighting, can be turned off. Motion sensors can be used for bi-level switching or automatic shutoff of outdoor lighting based on occupancy.
7) Use low pressure sodium lamps judiciously. While low pressure sodium lamps are a solution for astronomy, they may not be right for many outdoor applications.
“Only use LPS where you have to,” says Ibbitson, citing concerns about the quality of the light produced.
8) When addressing light trespass, Ibbitson advises: “Most of the time, it is easier to control light from within. In other words, light from the middle out, not the perimeter in. Use the right reflectors for the job. Avoid using external shields at all costs; nobody likes them. Use house-side shields only as a last resort. Look at the vertical light plane in areas where there may be concerns, and not just at the horizontal ground plane.”
9) Become educated about light pollution issues and educate your customers.
Software Can Help
3dOP, ALLSCAPE’s 3D outdoor lighting visualization program for PC and Mac users, was developed to help designers find the right lighting solution for their projects by enabling them to visualize performance with 3D output, explore options, and compare fixtures and reflector types, using a simple tool which provides instant feedback. The software has recently been updated with tools to analyze designs for glare and dark sky.
3dOP is available free and works with standard Type C IES-format files from any lighting manufacturer. The ideal use of the software is to determine the best placement of the fixture in the ground, on a wall or in the air. Working with Type C IES-format files, the most common type of IES file for outdoor fixtures, 3dOP allows users to position fixtures in one of three orientations and explore how light from a fixture is projected onto a wall, or the ground as the fixture position is changed dynamically. After creation, the user’s design can be output as a printed or electronic report.
“Rather than take a metric-only based approach to the dark sky issue, as there really is not one yet, we decided to provide the user with a graphical solution that allows them to explore the issues,” says Ibbitson. “Metrics are provided such as the cutoff classification, fixture efficiency and lamp efficacy, which act as tools to help users make the best design decisions.”
3dOP can work on virtually any modern PC with a current graphics card, while Mac users need OSX 10.3 or higher.)
Besides dark sky, new software features include photo rendering and statistical calculation.
Dark Sky: The dark sky module operates on three screens: the dark sky screen, the relative intensity screen and the absolute intensity screen.
The dark sky screen, like all the others, places the fixture inside a cube and projects the light from the fixture onto the cube’s inside walls. This immediately gives the user a graphical image of the light distribution in all directions. The user can set a glare zone range (default setting is 80-90 degrees) to whatever they want. Light in this zone is colored blue; light above the zone is red; and “good light” below the glare zone is colored green. The intensity of the light is also projected onto the walls.
The relative intensity screen uses the same information but codes the light into intensity bands-i.e., 0%-10%, 11%-20%, etc. Each band is color-coded, with red being the hottest and blues the coldest. It is just like a thermal image, but for light. The user can immediately identify the hot spots and determine if glare is going to be an issue in any direction.
The absolute intensity screen provides real fc/lx calculations on the cube walls for a user-set distance to the center of the cube. This can be useful to see what quantity of light is emitted upward or gets thrown onto the vertical cube walls. This can help determine if up-light is a real problem or if glare is a real problem.
Photo Rendering: This module enables the user to view a photorealistic rendition of the light out of the fixture onto the grid. It only simulates the direct light and does not take into account reflections (this capability will be provided in a future version). Similar to using a camera, the module comes with automatic and manual exposure settings, which allow the user to set the light level to get the best result. “The great thing about this feature, as with the rest of the software’s capabilities, is the real-time update,” says Ibbitson.
Statistical Calculation: This module allows the user to create a rectangular or circular area on the lighting grid where the light is projected; the software calculates the max, min, average and max/min fc/lx based on the area. These values change as the fixture is moved or as any other parameter is changed, allowing the user to explore the results as areas change.
“These new features enhance the 3dOP package further and allow the designer to explore and indeed see the light,” says Ibbitson. “They allow the designer to make more informed choices of fixtures or reflectors and allow him or her to show their clients what the design will look like.” The updates, he says, are based on user feedback, which he hopes will keep coming by writing to him at mailto:3dopSupport@allscape.net.
To download a free copy of 3dOP Dark Sky, go to
www.alllighting.com and click on the 3dOP button.
Craig DiLouie, principal of ZING Communications, Inc.
(www.zinginc.com), is a consultant, analyst and reporter specializing in the lighting and electrical industries.
