e-News #88: Outdoor Lighting

December 16, 2012
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More Light is Better…Or is It?

We need light outdoors at night for safety, security, productivity, and enjoyment. Guidelines and technologies available today can help meet these lighting needs while providing good quality lighting that minimizes light pollution, conserves energy, and enhances community ambience, including the effect on wildlife and our view of the starry night sky.

Figure 1Figure 1: Lack of directional light control in the left photo makes it more difficult to see.

Image courtesy of the Illinois Coalition for Responsible Outdoor Lighting.

At nighttime, the human eye adapts to the brightest light level in our field of vision. Figure 1 demonstrates this phenomenon well. The person standing next to the light pole in the right-hand side photo is almost impossible to see in the photo on the left-hand side. The only difference between the two photos is that that the bright source of light in our field of view in the left-side photo is blocked in the right-side photo; once the source of the lighting glare is removed we can see the person leaning against the light pole. This shows how without directional control, too much light actually makes it more difficult to see. Similar situations occur daily such as using a hand to shield direct sunlight or the headlights of an oncoming car.

Controlling glare is an important safety design element for any outdoor lighting application, from pole lighting in parking lots to building mounted wall packs. Controlling glare also reduces light pollution, the unwanted and excess lighting that strays outside the design area and often causes detrimental environmental effects.

Guidelines & Regulations

Guidelines, regulations, and green building programs address safe lighting levels, energy consumption, and light pollution. The Model Lighting Ordinance (MLO) is a generic ordinance directed at reducing light pollution and meant to be adopted by various municipalities. These guidelines greatly impact the design community in their efforts to implement better lighting practices.

Figure 2Figure 2: This diagram of the BUG fixture classification system relates the amount of light emitted at different angles, to potential for light pollution, wasted energy, and glare.

Image courtesy of IESNA MLO User's Guide.

The Illuminating Engineering Society of North America (IESNA) establishes light levels that designers use to ensure enough light is available for the task. Most designers know the IESNA as an organization that publishes recommended light levels for safe and effective lighting design. One such IESNA standard for the outdoor lighting industry is Lighting for Parking Facilities RP-20-98. This standard addresses the amount and distribution of light; it calls for a minimum horizontal illuminance level of 0.2 FC with a maximum to minimum uniformity ratio of 20:1. The relatively new guidance document, TM-15-07 from the IESNA designates a luminaire classification system designed for evaluating and comparing outdoor light fixture choices. This classification system, more commonly known as the BUG system, provides a means of evaluating fixture optical performance related to three zones of stray light: Back Light, Uplight, and Glare (BUG) from Forward Light. The BUG system is increasingly becoming nationally recognized and viewed as a tool that can help alleviate the increase in light pollution.

Designing Responsible Lighting

The Model Lighting Ordinance (MLO) was developed jointly by the IESNA and the International Dark-Sky Association (IDA) as a guide for designing responsible lighting, and is based on the ASHRAE Standard 90.1-2010 that updated lighting standards in regard to energy use. The MLO, published in June 2011, is an ordinance that can be referenced by or adapted as a section of a municipal code. Rather than addressing a fixture's optical design, the MLO creates light zone designations that specify the maximum allowable light levels and vertical illuminance levels at the site boundary. For instance, in a high density residential area, designated as LZ2 in the MLO, lighting installed would need to meet the allowed lighting level of 2.5 lumens/ft2. The MLO also limits interior lighting that spills outside at nighttime.

The light levels shown in Table 1 are from the MLO User's Guide and are meant to align with light levels recommended by IESNA.

Table 1: Some of the MLO's recommended lighting levels based on application.

ZoneDesignationRecommended AreaBase Allowance lumens/ft2 hardscape*Maximum vertical illuminance at site boundary
LZ0 No Ambient Lighting Wilderness, parks, preserves, undeveloped rural areas 0.5 0.05 FC
LZ1 Dark Rural and low density residential 1.25 0.01 FC
LZ2 Low High density residential, light commercial 2.5 0.30 FC
LZ3 Medium Large city business districts 5.0 0.80 FC
LZ4 High High intensity business districts, not appropriate for most cities 7.5 1.50 FC
*Allowed total initial lumens per site for non-residential outdoor lighting, hardscape area method. See MLO for full details.

The MLO-established light levels can be very useful in the circumstance where businesses want to capture your attention with a brightly illuminated sign. In these situations, cities often are left with the aftereffect of ever spiraling light levels. The State of California adopted the MLO to help eliminate these situations, as all lighting installed in the same lighting zone needs to meet the same light level standards.

Green building programs, such as the LEED Green Building Design and Construction certification program, award credit for reducing light pollution as well as reducing energy consumption. These programs reference standards such as ANSI/ASHRAE/IESNA Standard 90.1-2010 which establish lighting power densities (LPDs) for buildings, excluding low-rise residential facilities. Table 2 provides examples of recommended lighting power densities found in this standard.

Table 2: Example lighting allowances from ASHRAE Standard 90.1-2010, Table 9.4.3B - Individual Lighting Power Allowances for Building Exteriors.

ApplicationZone 0Zone 1Zone 2Zone 3Zone 4
Uncovered parking areas and drives No allowance 0.04 W/ft2 0.06 W/ft2 0.10 W/ft2 0.13 W/ft2
Walkways less than 10' wide No allowance 0.7 W/linear foot 0.7 W/linear foot 0.8 W/linear foot 1.0 W/linear foot
Walkways greater than 10' wide, plaza areas No allowance 0.14 W/ft2 0.14 W/ft2 0.16 W/ft2 0.2 W/ft2
Building Main entries No allowance 20 W/linear foot of door width 20 W/linear foot of door width 30 W/linear foot of door width 30 W/linear foot of door width

Outdoor Sales Open areas

No allowance 0.25 W/ft2 0.25 W/ft2 0.5 W/ft2 0.7 W/ft2

Drive Through Windows

No allowance 400 W per drive through 400 W per drive through 400 W per drive through 400 W per drive through
Parking near 24-hour retail entrances No allowance 800 W per main entry 800 W per main entry 800 W per main entry 800 W per main entry

Current Technologies and Strategies

Standards, guidelines, and the BUG system of fixture classification all are useful tools when selecting outdoor light fixtures. Deciding the right fixture for the application also depends on a number of other factors including rated life of the lamp, maintenance concerns, color rendering of the light source, efficiency, overall brightness of the light, and availability of controls systems.

Outdoor lighting sources becoming more popular due in part to their color rendering capabilities are LED and induction lighting. LEDs have high vertical and horizontal lighting uniformity, are mercury-free, provide instant-on capability, have stable color over the life of the lamp, and also offer good light control. Their disadvantages include variation in product quality among manufacturers and increased up front cost. However, their energy savings potential is hard to ignore. Induction lighting has similar advantages to LEDs, providing a lot of light in a small package. However, the up-front costs of induction lighting also often are high.

According to Lighting the Clean Revolution, the rise of LEDs and what it means for cities, LEDs provide energy savings of 50 to 70 percent compared with conventional outdoor lighting technologies. The LightSavers global 2.5-year LED trial sponsored in part by The Climate Group and Philips Lighting, involved 12 cities across four continents with the goal of accelerating the use of outdoor LED lighting and providing certainty about the technology.

The instant-on capability of LED and magnetic induction lamps make them well suited for use with lighting controls. Unlike HID sources that require a restrike or warm-up period after being turned off, these sources can be dimmed to lower lighting levels or turned off, with no wait period to return to full light output.

Lighting controls can be used to turn lights on and off, alert maintenance staff to energy usage or burned out lights, or to dim fixtures to a lower light level. Many nighttime lighting applications do not require full light levels after certain hours, for instance an hour after businesses close. Fixtures that can accommodate switching to a lower light level would reduce energy consumption and light pollution. The MLO addresses this idea of a lighting "curfew" by requiring outdoor lighting be reduced by a minimum of 30 percent. Examples of controls include time clocks, photo sensors, motion detectors, and energy management systems. Exciting new predictive occupancy technology makes use of wireless sensors and occupancy sensors to predict a person's path of travel, for instance on college campus paths or pedestrian walkways, and adjust light levels accordingly for use.

According to the MLO User's Guide, "some police departments have indicated that post-curfew light reductions make drive-by patrolling easier because it allows them to see further into and through a site". It is clear that increased night lighting decreases the fear of crime but results are mixed on whether it reduces actual crime. Perceived public safety increases when nighttime lighting is used as a crime deterrent but the quality of lighting is critical. The deep shadows created by glare-inducing fixtures actually can make people less safe by hiding suspects in shadows.

Impacts of Bad Lighting, Better Lighting

It is estimated that California cities could save more than $675 million through the next 15 years with economic streetlight upgrades. According to research conducted for the recently published "The State of Street Lighting in California, 2012", the California Lighting Technology Center at the University of California - Davis found that 76 percent of the 1 million street lights in 212 California cities use high-pressure sodium lamps, which could be upgraded.

The City of Los Angeles converted 140,000 high-pressure sodium fixtures to LED fixtures for a total implementation cost of $57 million and a 7-year payback. Energy savings were more than 68.5 Mwh/year and carbon emissions were reduced by 40,500 tons annually.

According to "Energy Savings Estimates of Light Emitting Diodes in Niche Lighting Applications," prepared for the U.S. Department of Energy, 100 percent LED penetration for parking lot and roadway lighting would save over 16 Twh/year and 20 Twh/year respectively

To help offset the increased first cost of LED fixtures, more than 20 California cities have made use of ARRA-funded Energy Efficiency Conservation Block Grant funding to change their outdoor street lighting to LED.

The federally funded National Optical Astronomy Observatory (NOAO) reports that poorly-aimed, unshielded outdoor lights waste $2 billion (17 billion kilowatt-hours) worth of energy in the U.S. each year. It is obvious that indiscriminate and excess lighting is a waste of energy and money.

And bad lighting doesn't just impact people. The Golden Gate Audubon Society indicates that more than 250 species of birds migrate through San Francisco Bay, mostly at night. Because it is thought that birds use stars as navigational tools, excess nighttime lighting can draw birds off course. Birds have been disoriented by brightly lit buildings or drill rigs which can cause them to fly in circles until they slam into the structure or drop from exhaustion. The Lights Out voluntary program has been developed so that all unnecessary nighttime lighting is turned off.

Yet even with better outdoor lighting - energy efficient or appropriate fixtures by application use - there are side effects that come into play, most typically at night. Figure 3 shows North America as viewed from space. It is a stunning image in its exposure of wasted electrical light. For astronomers, this over exposure creates challenges in viewing space from the surface of the planet.

Figure 3Figure 3: The earth pictured from space, with North America shown at night.

Image courtesy of NASA.

While astronomical observatories are located in some of the most remote areas of the earth, light pollution remains an inevitable challenge. Astronomers favor lamp sources that limit their light output to as narrow a portion of the spectrum as possible, leaving the rest for observation. Low pressure sodium lamps fit the bill. These yellowish lights don't do a great job of rendering colors, which makes them unpopular. LED and metal halide lamps are becoming increasingly popular for outdoor applications, due in part to their energy efficiency and color rendering capabilities, but they are broad spectrum sources of light. These deliver an even greater challenge for astronomers; because they emit light across the spectrum, they interfere at more wavelengths. The white light they emit is a shorter wavelength and more easily scattered in the atmosphere, which increases sky glow and reduces night sky visibility.

Utility Lighting Education and Incentives

There are many reasons to pay attention to the choice of outdoor lighting. Money and safety are usually among the top two, but economic development, maintenance, and cost to install also are factors in outdoor lighting decisions.

California utilities offer their customers educational opportunities for learning about lighting and range from selecting the proper lighting systems by application use, to improving knowledge of technologies and their performance characteristics - and how to maximize possible utility incentives and available rebates.

Southern California Edison

Residential Lighting Incentives
Commercial Lighting Incentives

San Diego Gas & Electric

Residential Lighting Incentives
Commercial Lighting Incentives

Pacific Gas and Electric

Residential Lighting Incentives
Commercial Lighting Incentives

Training Highlights

California utilities offer outstanding educational opportunities that focus on the design, construction and operation of energy-efficient buildings. Listed here are a few of the many upcoming classes and events; for complete schedules, visit each utility's website.

Computer Aided Lighting Design
December 18 (8:30 am to 12:30 pm)
Energy Education Center - Irwindale
register >

Introduction to Lighting
January 9 (8:30 am to 12:30 pm)
Energy Education Center - Irwindale
register >

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e-News is published by Energy Design Resources (www.energydesignresources.com), an online resource center for information on energy efficiency design practices in California.

Savings By Design (www.savingsbydesign.com) offers design assistance and incentives to design teams and building owners in California to encourage high-performance nonresidential building design and construction.

Energy Design Resources and Savings By Design are funded by California utility customers and administered by Pacific Gas and Electric Company, Sacramento Municipal Utility District, San Diego Gas and Electric, Southern California Edison and Southern California Gas Company, under the auspices of the California Public Utilities Commission.


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