|Green Cobra LED streetlight, Los Angeles, CA
Photo Credit: Leotek
Exterior retrofits can provide all the energy and performance benefits of interior retrofits--with an entirely different set of implications for the world outside. They can reduce light pollution and bring back the night sky, all while improving energy efficiency and visibility. This month, we continue our discussion on retrofits but with a focus on the outdoors--both commercial exterior and streetlights. We begin with a discussion about the adverse effects of poorly selected and managed exterior lighting followed by our Chapter Spotlight, outlining best practices for exterior retrofits with links to approved fixtures and a User's Guide for the Model Lighting Ordinance.
| Bringing Back the Night Sky
View of Los Angeles from Mt. Wilson in 1908 (left) and 2007 (right). Left image courtesy of the International Dark Sky Association. Right image courtesy of the UCLA Department of Physics & Astronomy.
Urban and developed areas throughout the world have added electric lighting to support the nighttime activities of humans. That lighting can have unintended consequences. Mounting evidence (visit ALG Online's Policies & Programs chapter) indicates negative impacts on a wide range of flora and fauna, including humans, in addition to wasted energy and money. The term light pollution was originally coined by astronomers to describe the clouding of the skies at night from urban skyglow, reducing visibility of the stars. Light trespass occurs when rays from overlit cities and suburbs, light-flooded highways and parking lots, or simply from adjacent properties illuminate unintended areas.
Light pollution is largely the result of bad lighting design, which allows electric light to shine outward and upward into the sky, where it's not wanted or needed, instead of focusing it downward, where it belongs.The International Dark Skies Association (IDA
) estimates that an annual average of 22,000 gigawatt-hours of lighting energy is essentially light pollution. A successful design will balance the potential tradeoffs between specialized technologies, energy use, costs and maintenance concerns. See our Chapter Spotlight for more details on outdoor applications.
ALG Online's Design Considerations
chapter discusses the methods, tools and reasoning behind best practices that ensure truly advanced lighting design--those that take comfort, performance, energy, environment and the bottom line into account. Explore
for more details on light pollution. Not a subscriber? Join now
or try 5 days of free access
It's clear that both visual and environmental quality are adversely affected by poorly chosen and managed outdoor lighting--from landscape lighting to stadiums and interstates. Exterior retrofits provide an opportunity to address these challenges.
Exterior Retrofits for Street & Area Lighting
Owners can derive significant benefits from replacing existing outdoor luminaires. Not only can such upgrades improve energy efficiency (by 35-80% in some cases) and thereby reduce owner energy costs, they can generate other benefits such as improved color rendering, light distribution and longer rated life (resulting in less maintenance).
There are many options available to replace the older light sources of mercury vapor, high-pressure sodium (HPS), probe-start metal halide and incandescent/halogen. Alternatives include LED, plasma, induction and electronic-ballasted HPS and pulse-start and ceramic metal halide systems. LED retrofit kits are LED luminaires or array-and-driver packages that replace pole-mounted HPS, metal halide, mercury vapor and incandescent outdoor luminaires or lamp-ballast systems for significant energy savings. All new luminaires should feature optics that not only maximize efficiency and minimize glare, but also minimize skyglow and light trespass. Review a list of approved exterior lighting fixtures
from the IDA and check out our Roadway Luminaires (PDF) for more information on using exterior pole-mounted luminaires, the BUG rating system and Lighting Zones.
IDA and Illuminating Engineering Society of North America (IESNA) have developed the Model Lighting Ordinance (MLO) to address the need for strong, consistent outdoor lighting regulation. Explore the MLO User's Guide, which will walk you through this recommended set of standards.
For more about LED retrofits and kits, subscribe now to explore Exterior Retrofits in ALG Online's Luminaires & Distribution chapter.