OUTDOOR LIGHTING - WHAT'S THE HARM
We have been encouraged to think that lighting is always good, never bad or excessive. However, inappropriate outdoor lighting alters the nocturnal environment, contributes to global warming by wasting energy, offend neighbors with light trespass, can attract crime, and create safety and human health risks.
Do you know that:
- The American Medical Association issued a public statement in 2012 on the health and environmental risks of exposure to light at night, and issued a second statement in 2016 concerned with the high blue light content of some LED fixtures in our outdoor environment.
- Ambient light has become so prevalent that it is impacting insect and animal reproduction, migration and feeding.
- A 100-watt bulb left on all night for a year produces nearly half a ton of carbon dioxide if power by coal fired power plants.
- Improperly shielded fixtures waste billions of dollar's worth of energy each year into the sky hiding the stars with the waste light.
- There is no objective evidence that unmonitored dust-to-dawn lighting repels crime and may attract or facilitate it. A light on motion sensor is more likely to add security.
- Your local utility company offering "security lighting" likely has no expertise in security or lighting design.
Light Pollution Map of the United States
- There is no naturally dark night sky left in Arkansas.
In short, outdoor lighting has become a classic case of too much of a good thing, or in some cases, a seemingly good thing. Below we identify common inappropriate lighting practices and how to remedy them. Thanks for your interest in becoming a responsible lighting neighbor.
COMMON INAPPROPRIATE LIGHTING PRACTICES
There are four common features of inappropriate harmful outdoor lighting:
- Lack of proper shielding or improper aiming;
- Use of more light than is needed;
- Using the wrong color light;
- Leaving lights on all night or when otherwise not needed.
Each of these is illustrated below along with examples. In the next section, we look at the principles of responsible lighting.
Typical "barn yard" light wastes light up and out horizontally.
Improperly shielded or aimed fixtures throw light directly up into the sky. This wastes energy and hence needlessly contributes to climate change and is the prime source of sky glow - robbing us of the stars and impacting the esthetics of our towns and cities. (Right)
Note light shining up and out into trees.
Inadequately shielded fixtures also send light out horizontally across property lines where it may not be wanted, and resulting in uneven lighting and blinding shadows. It is said good fences make for good neighbors. So does good lighting. (Right)
Reading a book in backyard 260' from utility installed "security light"
Light shinning directly into the viewer's eyes can cause glare, which can be uncomfortable and even blinding. It results from inadequately shielded or misaimed fixtures that shine at or nearly horizontal. As you drive, notice how many roadside lights are impacting your vision. (See below)
Grossly over illuminated with a horizontally aimed utility fixture. Look at light going into the sky, how dark it is behind and to the right of the building and the thousands of bugs flying themselves to death in the too white light. Who cares? birds & pollinating plants for two.
Too much light can blind people to less well illuminated nearby places, creating security and safety risks. It wastes energy and contributes needlessly to sky glow. By definition it is too much of a good thing. The goal should always be to use the least illumination needed for the purpose at hand. (left)
Below we have it all: over illumination, horizontal light from an inadequately shielded fixture resulting in trespass, uneven illumination, shadows and up-light into the trees and sky - wasteful intrusion.
Utility installed "security lighting" horizontally aimed fixture with excess illumination blinds one to the less bright parking lot. Even illumination should be the goal.
LED lighting, while efficient, has a tendency to have a blue color. Blue is more likely to cause glare, impact dark adapted vision, scatters more in the atmosphere, hence causing more sky glow, and impact human, insect and animal biology. Use warm colored lighting outdoors.
Unmonitored dusk-to-dawn lighting can attract and facilitate crime rather that prevent or discourage it. The Illumination Engineering Society recommends lights on motion sensors for residential security applications, while timers or occupancy switches can turn off or dim lights in commercial settings.
FOUR RESPONSIBLE LIGHTING PRINCIPLES
- Where needed, using aimed and properly shielded fixtures;
- When needed, using switches, motion sensors and timers;
- In the amount needed;
- Using proper color.
IDA has provided an online selection tool to help with selection, and IDA approved fixtures can be found at most places that sell outdoor residential lighting fixtures.
Note: most utilities will retrofit "barnyard" lights with shields for small fee.
Up-light, trespass, glare - these have a common cause and share a common remedy. Proper lighting comes from above. Fixtures should not shine light horizontally or up. Standing level with the bottom of a light source, or even some below it, you should not be able to directly see the source. The schematic to the right, from the city of Fayetteville's lighting ordinance, illustrates the concept. On the left, compares old vs. new roadway lighting.
The switch is the most powerful tool we have to combat Light Pollution and wasteful lighting. Timers are not expensive and will pay for themselves in short order, as will motion sensors, and unlike static always on lighting, motion sensors actually can enhance security.
LED 8,040 lumens on left - Legacy HPS 19,000 lumens on the right.
IN THE AMOUNT NEEDED
When switching to a white light source, such as LED, from some heirloom technologies, it is a common mistake to use the same lumen rating. The result will be over illumination. As a rule of thumb you should cut the lumens by half or more as the eye is more sensitive to the white light. A low level of lighting is usually sufficient for outdoor navigation and retains your ability to see outside the illuminated area.
Too bright light turns the world around it totally invisible. The goal should be to provide the minimum light needed to the purpose so as to preserve maximum vision in the surround envionment
LED fixtures tend to have a blue spike.
To minimize adverse impacts of outdoor artificial lighting using LED technology, it is important to minimize the blue light content. Sources that produce a white light with a yellow cast are preferred over stark white or blue lights. A soft white, or better yet, warm white color is preferred. If looking at color corrected temperatures (CCT), under 3000K is recommended by IDA. In sensitive areas amber is ideal.
Harvard Health Publications.