Light Pollution: An Overview
Light pollution is any adverse effect of artificial light including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste. Denver suffers from serious light pollution caused by uncontrolled light directed up toward the sky. The good news is that light pollution is, in many cases, easier and less expensive to remedy than other types of pollution. And the changes can begin with your own choices about exterior lighting at night.

Examples of Light Pollution
A great example of light pollution is a post-top lantern, often nostalgic in style, which emits light in all directions. Standard "cobra head" streetlights, though they have an opaque top, emit light above a 90 degree angle, which means that they are not Dark Sky compliant. Another is billboard lighting that aims upward. A common residential offender is a lantern style fixture in which the bulbs are visible and the light escapes in all directions.
For local light pollution, look no further than 6th Avenue west of downtown. The floodlights between the access road and 6th Avenue mounted on poles, with regular "cobra head" streetlights below are much brighter than necessary, poorly positioned to light the road, and are a source of glare to drivers as well as the people who live nearby. Driving the Denver metro area, look for these "glare bombs" and post their location in the comment section at the bottom of the article. They're everywhere.

Why Is Light Pollution a Problem?
Remember lying in the grass as a child and looking up at the stars? Our children in Denver, as well as those of us who enjoy stargazing or taking in meteor showers, like November's Leonid shower, are missing out on that opportunity. Much more serious implications of light pollution include disruption in human circadian rhythms, sleep cycles, and immune system function, as well as a deleterious effect on animal reproduction. In addition, light directed at the sky is, in all cases, a waste of energy, no matter how exciting it appears. A closer look at the links between light pollution and human health issues will be explored in the other articles in this three part series.

How Can We Make It Better?
In an ideal world, we would no longer attempt to mimic the glow of daylight in our night time world, and instead, would lower all ambient light levels since the dark-adapted eye needs much less light than a bright-adapted eye in order to see.

Here's the good news. As individual citizens, we can make exterior lighting choices at our homes and workplaces that do not further light pollution. The International Dark Sky Association, which is dedicated to preserving dark skies and pushing for legislation to enforce dark sky compliance in communities, has published a list of fixtures that can be used in all types of outdoor applications without lighting up the night sky, angering neighbors, or wasting energy. Let's explore some common elements.

1. Assess your requirements. Determine where you really need light. Don't use light as "decoration" or for visual effect at night.
2. Direct light where it is needed. Remember that at night, less is more. Concentrate fixtures only where needed. Choose fixtures that can be aimed, and keep them aimed toward the ground.
3. Avoid glare. Glare actually compromises safety, as it can render an attacker or intruder invisible. Glare is often caused by an unshielded source, such as a fixture where the bulb is visible.
4. Use lower wattage bulbs. More light does not mean more safety. The dark adapted eye can best see at night when there is uniformity of illumination. A bright light against a dark background causes pupil contraction, so the dark background beyond the bright light is invisible.
5. Use "full cutoff" fixtures, which means that less than 1% of their light output is emitted above 90 degrees from horizontal.
6. Make sure that the light source is not visible when viewing the fixture straight on.
7. Keep in mind the motto "Lights Down, Stars Up".

For some Dark Sky compliant light fixtures, check out the International Dark Sky Association's approved fixtures or Skykeepers.org approved fixtures. Both websites are filled with information about dark skies and how to take action to minimize light pollution.

Resolve this year to take action on behalf of keeping our skies dark. Think of light pollution as light leak. If light fixtures were water faucets, and any light emitting toward the sky was a drip, we'd fix it immediately. Let's address light pollution with the same zeal we apply toward other matters of sustainability and energy waste, and encourage those around us to do the same. If your neighbors have bright lights that shine into your bedroom at night, check out this great resource on how to address the topic with diplomacy.

In the next two articles in our three part Dark Sky series, we'll address more specifics on fixture selection and how light exposure at night affects our health.

Originally posted 2010-02-07 00:01:34.

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Perception of light level also depends on the color temperature. The more blue-white the light, the higher the perceived light level, even when foot candles are the same. Warmer color temperatures are often perceived as a lower light level. This is useful when considering task versus ambient light; cool task lighting can provide more visually perceived light (helping the care provider), while slightly warmer ambient light can feel less intimidating (helping the patient).

High levels of contrast tend to portray excitement, but in the medical environment, can cause confusion for patients with aging eyes, and work against eyes of all ages as the eye's adaptation from dark to light takes time, and decreases with age; thus, the lower light level areas often feel dark, and the higher light level areas, painfully bright. We should strive for good uniformity in the medical care environment, especially at low light levels.

In a patient care setting, we need to consider two very different needs and experiences.

First, let's consider the needs of the care provider. There must be adequate light to examine skin color and texture, and shadows are important to see variation in skin, depth of lesions, etc.! That means that totally indirect light sources don't work for care providers doing critical exams unless there's also daylight. 3000-3500K (halogen color temperature) is typical, but I believe it's wise to mockup exam rooms with color temperatures ranging from 3000-4100K and let the practitioners give input on their preferred color temperature. It's feasible to have a portable exam light or local task lights such as recessed ceiling fixtures that are on during the critical part of the exam. The rest of the time, these lights do not necessarily need to be on.

Second, we must consider the patient experience. Indirect, lower level lighting that is warmer in temperature offsets the perception of a sterile, institutional exam room. With reasonable uniformity, the light levels won't seem low to the patient while they're waiting for the practitioner, and during any initial discussion. For patient purposes, low level 100% indirect light, like fluorescents over the exam cabinets reflecting onto a white ceiling, are soothing.

Let's not forget context. Corridors and halls are often dreadfully overlit. Realistically, between 5-15 footcandles, depending on the users, can get the job done, especially with good uniformity. When you go from a corridor that has 5-10 footcandles to an the adjacent space with 25-30 footcandles, the perception is WOW! This place is well lit! However, when you have 30 foot candles in the corridor, an exam room with similar average illumination feels dim, especially if that light is all on horizontal surfaces. By sensitivity to context, we increase the perception of brightness by keeping adjacent spaces at a lower light level as much as feasible.

We also need to consider the light reflectance value of the space's finishes. Lighter colored finishes create more of an overall perception of brightness.

As with all well-designed lighting solutions, there is not a one-size-fits-all approach.  We need to provide flexibility in controls that allow the lighting to be used in varying capacities, such as during the critical portion of an exam, versus when the patient is awaiting the care provider's arrival.  Flexibility and user control has been proven to decrease energy consumption and increase user satisfaction.  For that to be successful, the users must be "active users" and engage with the capabilities designed into the lighting system.

Originally posted 2010-07-22 00:42:23.

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Hi Doug. Your question is a great one, since lots of folks are now using compact fluorescent bulbs in their outdoor lights. Based on your comment about the bulbs looking too bright, it sounds like your fixtures might be lanterns that have a glass face so you can see the bulb.

Compact fluorescent bulbs (CFL's) can be successfully used in outdoor fixtures, but let's take a look at what we need to consider in order to use them successfully:

1. At night, the dark adapted eye does not need nearly the amount of light to see that is required under daylight conditions. This means that we do not need nearly the wattage in an outdoor fixture that we'd use inside. A 20W CFL bulb is MORE than enough (this equals 60-75 watt incandescent bulbs), and 13W or 10W bulbs (these equal about 40W incandescent bulbs) are even better.
2. CFL's require a minimum temperature to light up and to reach full brightness. The colder it is, the longer it takes a CFL to reach its full brightness. In a cold climate, like Colorado's, outdoor use of CFL's is a challenge in the winter.
3. The single biggest factor that affects fluorescent bulb life is the number of times the bulb is turned on and off. If you have a fixture on a motion sensor and it cycles on and off repeatedly, the bulb will fail much faster than one that is turned on and stays on for hours at a time.
4. CFL's are brighter to look at than incandescent lamps. This is particularly an issue in fixtures with glass fronts, which means that the light is spilling out in all directions. We want to choose fixtures where the bulb is not visible behind glass, or is at least concealed behind glass that's translucent and diffuse, not transparent.

So, how do we put all of these considerations to practical use?

• Use a much lower wattage bulb than what you would expect. In outdoor lighting, less is more!
• For fixtures in extreme cold or that cycle on and off frequently but don't remain on for long, use fixtures with integral LED sources or an energy saving halogen bulb. As LED technology continues to develop, LED replacement bulbs will likely be perfect for outdoor use, but they are not ready for the big time yet.  Stay tuned.
• Use twist-type CFL's only in enclosed fixtures or under eaves or overhangs, not in the open.
• Use fixtures with diffuse glass or, preferably, Dark Sky compliant fixtures, like these from Foothills Lighting.

In future columns, we'll address the importance of Dark Sky legislation, its links to both environmental sustainability and human health, and how to choose lighting that complies with Dark Sky standards.

Originally posted 2010-02-04 00:01:59.

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"Darkness is as essential to our biological welfare, to our internal clockwork, as light itself." -Verlyn Klinkenborg, "Our Vanishing Night," National Geographic magazine, November 2008

Last week in the first article of our three part series on Dark Skies , we took a look at the Dark Sky movement, some of the impacts and examples of light pollution here in the Denver area, and considered ways to choose exterior lighting fixtures that do not contribute to light pollution.

The effects of light pollution run far deeper than wasted energy in the form of light directed at the skies and minimized visibility of stars. More insidious impacts of light pollution are engaging a wider community than astronomers and sustainability advocates, such as cancer researchers and sleep experts.

From an evolutionary standpoint, human lives have long been regulated by night (dark) and light (day) cycles. Light/dark cycles regulate our internal timeclocks, or circadian rhythms, and are critical for the production of hormones and immune system function.

For thousands of years, our ancestors woke with the rising sun and went to sleep when cued by darkness. Until the industrial era, firelight, and later, gas lamps, were the only “artificial” light available after nightfall. Even then, artificial light was characterized by a golden glow similar to the warmth of a dimmed incandescent bulb.

Our nighttime world stands in marked contrast to this. Viewing a map of the earth at night, our cities glow like stars in the sky, and we have worked assiduously to render the night a replica of day time through excessive use of artificial light, certain that this makes us more secure.

What have we accomplished? Numerous studies indicate that high levels of artificial light do not create a safe night environment. In our quest for security, we have managed to skew circadian rhythms and, in the last 80 years alone, render more damage to our ability to sleep, our immune system function, and our blood sugar regulation than our predecessors managed to achieve in thousands of years.

Various studies from locations around the globe show increased cancer risk among women in industrialized countries, as well as shift workers. What do these people have in common?  Exposure to artificial light at night.

Dr. George Brainard, a researcher at George Washington University who studies the impact of light on sleep cycles, notes the impact of a light on participants in sleep lab research. Participants slept in a completely darkened room. After control data was taken, a light emitter the size of a dime was taped to the back of each participant’s knee. The effect of this minimal amount of light on the skin? Sleep cycles were significantly disrupted, and immune system function was suppressed. Any light exposure at night, particularly in the cooler (more blue) portion of the light spectrum, suppresses melatonin production, which in turn promotes wakefulness. And with melatonin suppression comes diminished Natural Killer cell (NK) and T cell production, the front line of immune system function.

The danger of night time light’s effect on human health is significant enough that the conservative American Medical Association (AMA) has voiced a formal position decrying the impacts of light pollution and recommending immediate action to minimize it. According to the AMA, "Light trespass has been implicated in disruption of the human and animal circadian rhythm, and strongly suspected as an etiology of suppressed melatonin production, depressed immune systems, and increase in cancer rates such as breast cancers." Find more information on this important step in supporting Dark Sky legislation here.

As individuals, we can take action in our homes to guard ourselves against the effects of light trespass. Add blackout curtains or blinds in bedrooms to make sure they are completely darkened at night. If a light is required, such as in a child’s room, use a nightlight in the amber or red portion of the spectrum, which is shown to have much less impact on the dark-adapted eye and circadian rhythm than light in the blue portion of the spectrum. Talk to neighbors to respectfully request that their glaring spot light is redirected and shielded.

The next step is to eliminate the sources of light trespass outside the house. In our third and last article in this three part Dark Sky series, we will consider ways to interact with the community at large to promote Dark Skies and enact regulations for Dark Sky compliant lighting.

Originally posted 2010-02-10 00:01:30.

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Oops! #1:  Putting recessed downlights (can lights) everywhere. This is one of the most common errors that lighting design professionals see. Can lights can be very inexpensive, and people often assume that laying them out in a regular grid gets light everywhere.  Unfortunately, this is not so.  The optics of inexpensive can lights often allow only slightly more than half the light of the lamp (bulb) to escape. What a waste!  In addition, can lights, unless they are adjustable or wall wash fixtures, typically don't put sufficient light on vertical surfaces, which is where the eye perceives light.  With an array of cans, we might waste nearly half our watts and still have a space that feels like a cave.  Also see Oops! #7.

Oops! #2:  Forgetting task lights in the kitchen. The idea of adding a row of can lights over the counter falls under the category of Oops! #1.  There are many better ways to light the counter, and one of them is to use fluorescent (T5), xenon or LED task lights under the upper cabinets.  We do not recommend halogen because of its heat output.  If your kitchen lacks upper cabinets where you're doing work, despair not! This is a situation where wall-mounted or ceiling recessed adjustable fixtures with the right lamp (bulb) make all the difference.  Adding several low voltage halogen fixtures with a narrow flood beam distribution and focusing them on the task area will also work well.  Remember to choose your fluorescent or LED color temperature wisely.

Oops! #3:  Using downlights over the vanity without adding lights on the side. Remember the grade school trick of holding a flashlight under your face and seeing the shadows magnify your visage into a gruesome caricature?  The same is true in reverse.  Standing directly under a downlight, without any light at the sides of the face, creates exaggerated and unflattering shadows.  In the bathroom, using a downlight over the sink is fine to accent the expensive polished nickel faucet you've chosen, but it's insufficient for tasks like shaving, tweezing, and applying makeup.  For this, we need light at the sides of the mirror at eye level to minimize shadows and provide even distribution.  This can be achieved with sconces flanking the mirror.

Oops! #4:  Using incandescent or halogen bulbs without dimming. While we are all finding ways to retrofit lighting with more efficient, longer lived light sources than incandescent, it is still a viable and very important part of lighting in a residence, as long as it is dimmed.  By dimming, we decrease energy and heat output, and we elongate lamp life.  It's important to train yourself and your family to dim incandescent sources as low as you can tolerate them.  For more in depth information on this topic, read here.

Oops! #5:  Forgetting to incorporate ambient, task AND accent lighting. Lighting designers understand that all well-designed spaces incorporate different types of light.  Ambient light is general lighting for walking around, conversing, and identifying objects.  Task lighting provides higher, more concentrated lighting for tasks such as chopping vegetables, shaving, or reading.  Accent light is used to highlight artwork or architectural features, such as beautiful tile in the bath or the glass collection in your kitchen shelves.  Combining all three types of light gives greater functionality, interest, and likelihood that you will have sufficient lighting.  Also see Oops! #6 below.

Oops! #6:  Neglecting to control different types of light separately. As mentioned in Oops! #5, it's important to combine different types of light in each space.  For maximum efficiency and flexibility, each type of light should be controlled separately, and any incandescent or halogen light, or dimmable LED's (check with the manufacturer for specific requirements) should be dimmed.  Controlling multiple sources can be achieved by the old school method of multiple light switches, but there are many more sophisticated ways to achieve control. From a simple programmable wallbox system for single room control with preset scenes, to wireless controls that generate their own power and can be reprogrammed from your laptop or phone, controlling the lighting means you save energy while getting the light you need.

Oops! #7:  Putting recessed downlights in a high ceiling for ambient light. A corollary to Oops! #1, this tactic results in a lot of wasted light and a very dark space.  Light originating at high ceilings needs to have a very focused, tight beam spread, or be reflected off the ceiling.  With a high ceiling, reflecting light off a light, matte ceiling surface often provides much better illumination than punching a lot of holes for recessed downlights.

Oops! #8:  Choosing dark colors everywhere without adjusting the lighting. While dark, saturated colors can provide a very enticing interior setting, they absorb light, requiring more energy for the space to have the same illuminance level as one with paler colors.  Many LEED-certified buildings, such as the U.S. Green Building Council's new headquarters, use white or pale colors as a way to reflect as much light as possible.  This can create a significant energy savings since both daylight and artificial light are reflected deep into the space. Where possible, limit use of dark colors to spaces where task lighting or high lighting levels are less critical, like powder rooms that aren't used as full baths, formal dining rooms that do not double as work spaces, or on accent walls or trim.  If you must use dark colors in spaces where higher light levels are needed, add additional light sources and use higher wattage lamps.

Oops! #9:  Decorating with light. Lighting designers think about light as an actual dimension, imagining the distribution and output from each fixture, as well as the quality of the light and color.  Decorating with light fixtures, or choosing fixtures based on how they look rather than their light output, performance, and distribution often results in a waste of energy and less than optimal light output.  For assistance with architectural (and yes, decorative) light fixture choices, consider hiring a professional lighting designer who can transform your space through light, while providing adequate task lighting and often saving energy.

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• Existing lighting conditions evaluation
• Energy usage and code analysis
• Interior and exterior lighting layouts
• Energy code calculations and ComCheck compliance forms
• LEED calculations and documentation for lighting
• Architectural and decorative lighting fixture plans
• Architectural and decorative lighting fixture specifications
• Lamping plans and lamp specifications
• Controls plans and specifications
• Custom fixture designs
• Daylighting analysis
• Final drawings for bid or construction
• Construction phase services including site visits and project meetings, submittal review, and coordination with team members

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In the first article of our three part Dark Sky series, we defined light pollution and examined choices for exterior lighting that do not contribute to light trespass.

Last week in the second article of our three part Dark Sky series, we investigated the physiological impacts of exposure to light at night and ways to mitigate effects on circadian rhythm and immune system function.

The most successful way to keep our night skies dark or reduce skyglow in urban areas is by spreading the word, increasing awareness, and encouraging your community to adopt a model lighting ordinance that requires outdoor lighting fixtures to be Dark Sky compliant.

• Start at home. Ensure that your own exterior lighting is Dark Sky compliant. Dark Sky compliant fixtures direct light to the ground, not the sky, and are shielded to minimize glare. Dark Sky does not mean dark ground!  A great visual summary can be found here and a residential lighting retrofit with comparative photos can be found here.
• Talk to your neighbors.  If your neighbors have a bright light that's intrusive, consider it a chance to increase awareness.  According to the International Dark Sky Association (IDA), "Suggest a lower wattage, fully shielded light with a timer and/or motion sensor as a way to light property for security but with minimal effect on neighbors." Need more ammunition? Here's a great resource.
• Get involved in the community by encouraging code officials to adopt a model lighting ordinance that requires new outdoor lighting to be Dark Sky compliant.  Begin with seeking out a contact in your community, preferably on the planning commission or town council.  Encourage the municipality to add a lighting ordinance that meets these guidelines.  A more thorough model lighting ordinance is being finalized by the IDA and is also a valuable resource.

Colorado is considered one of the most progressive states in enacting and enforcing lighting ordinances. Wondering if your community already has a lighting ordinance that discourages light trespass, and is enforceable (not just guidelines)?  Counties and municipalities near Denver with lighting ordinances (provisions vary) include:

• Arapahoe County
• Arvada
• Aurora
• Avon
• Boulder County (excluding the Niwot rural community district)
• Boulder
• Castle Rock
• Douglas County
• Fort Collins
• Frisco
• Gilpin County
• Jefferson County
• Longmont
• Monument
• Pueblo County
• Wheatridge

Links to the codes can be found here.

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What in your house has an on-off switch without settings or options? Your washer has cycles; your hair dryer has heat settings; your fans go in two directions. But your lighting? Well, that’s another story. Of the 37 wall switches in the average American house, only 2.7 of them are dimmers.

Dimming incandescent bulbs is a great way to save energy in your home without putting compact fluorescent replacement bulbs in all your light fixtures.

Did you know that if you dim a bulb by 10%, you use 10% less electricity and double the bulb life? If you dim a bulb by 25%, you use 20% less electricity and quadruple the life. And if you dim a bulb by 50%, you use 40% less electricity and increase the bulb life twentyfold. How does this work?  Simple!  Dimming reduces the amount of heat on the bulb's filament, which helps it last longer.   You can calculate energy savings by dimming here.

Replacing a standard on-off wall switch with a dimmer is a simple exercise that someone with average skills can do. There are plenty of options from the original rheostat, or rotary dial wall dimmer, to touch dimmers with LED indicators. By taking on a simple wall switch replacement, you CAN retain that candlelit glow and save energy. Just make sure to dim the lights to the lowest level that works for the way you are using the space, and coach your family or housemates to do the same.

In upcoming columns, we'll examine how the incandescent bulb is being reinvented to meet new energy standards as well as viable compact fluorescent replacements, and where to use what so that your home remains comfortable and well-lit without depleting resources.

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