Designing for Darkness

Designing for Darkness

By Kate Hickcox

What is designing for darkness? There are many overlapping areas of concern when it comes to designing for darkness and LAN. The research conducted in 2019 focused on 26 current organizations that are focused on nighttime or “dark sky” issues. As expected, most organizations were concerned with issues of astronomy, natural character, and energy waste, while others focused more on plant or animal issues. Most of the organizations listed multiple main areas of interest in their literature. From this research, nine main areas of focus were identified that could be categorized into five sub-groups of LAN concerns. These include:

• Human health, comfort, and safety

• Concerns about animals and wildlife

• Astronomers’ and the military’s concerns about astronomy

• Energy waste

• Preservation of natural character (respecting the aesthetics of the natural environment)

These five sub-groups of LAN concerns could then be divided into three major areas of LAN concerns to create a framework for approaching designing for darkness. The three major LAN concerns include sky glow concerns, human-focused concerns, and ecosystem concerns.

While each of these areas has very different stakeholders and design needs, a similar design approach can be adopted in each case. Each of these areas should be addressed using these criteria:

• timing (and duration)

• directionality

• intensity

• spectrum

In 2021, Kate Hickcox created a Designing for Darkness poster that illustrates the interconnections between humans, the ecosystem, and skyglow. The poster gives details about how to approach designing for darkness using the criteria listed above. (The poster is available in the original publication.)

If you are designing, specifying, or evaluating a lighting system in an outdoor nighttime environment, you need to ask:

• WHO or WHAT will be experiencing this system?

• WHY is the light necessary here? Do we really need lighting at all?

The who or what can be a wide variety of end users or end scenarios that should be researched and considered before a lighting solution is reached. Always ask if the specified lighting is necessary, or could it be removed? A good lighting specifier knows when not to specify lighting as well as how to specify quality lighting when it is needed.

Photo Credit: Adobe Stock | Milan Noga reco

Directionality of the Lighting Is Key

Controlling the spatial distribution of light, including the reduction of direct uplight, is one of the most impactful ways to reduce sky glow at the luminaire level. Shielding is a common technique for reducing the effects of lighting on natural lands and species. Fixtures that allow no light to escape directly up to the sky are important as this can decrease sky glow and reduce attraction from birds or insects above the fixture. Consider these tips:

• Zero direct uplight can greatly reduce sky glow

• Support wildlife by specifying shielding to prevent direct views of the light source

• Shielding can also help to reduce glare for humans.

Reduce Intensity or Light Output Whenever Possible

Regardless of the spectral content, a reduction in light output has a significant effect on sky glow. When designing for ecologically sensitive installations, even very low lighting (far below that of the full moon) can have large effects on local wildlife and plants. Lighting codes and recommendations are usually written to support human tasks and needs and may therefore be excessive for wildlife and plants. The luminous output recommended for typical applications may be much higher than necessary if you are installing in a rural environment or a natural park.

When designing any outdoor lighting:

• Reduce light output as much as possible.

• Allow for controls such as adaptive dimming or switching. Timing and output are determined by tasks/needs.

• Less is always better for wildlife and ecology.

Importance of Timing and Duration

It would be easy to assume that turning outdoor lighting off during a curfew period could only have a positive impact on the local ecology. However, some species are very sensitive to how and when the lighting changes. Lighting that turns on or off at irregular intervals, or lights that disrupt fixed nighttime patterns, may disrupt the nocturnal behavior of some species. Wildlife and plants are sensitive to changes in both intensity and spectrum during dawn and dusk. When designing for darkness, remember:

• Allow for controls and dimming.

• Timing is species dependent.

• Ask an expert for ecologically sensitive installations.

Spectrum Can Make a Difference

Address timing, distribution, and output first; in many cases, these will have the greatest impact.

When considering spectral choices for an installation, remember that correlated color temperature (CCT) does not determine spectrum. Two sources with the same CCT can have very different spectra, and thus different impacts on the environment or on wildlife. Keep in mind that there is no universal spectral solution. Across the range of visible wavelengths, there are advantages and disadvantages in each spectral band, depending on the species or environment. Different installations or tasks may require different spectral selections. One rule that can have a big impact and is relatively easy to enforce is to avoid any ultraviolet spectrum and adjacent short wavelengths, as some wildlife are highly attracted to ultraviolet radiation. Keep in mind:

• Limit short wavelengths to help reduce sky glow.

• Spectral selection for wildlife and ecology is species dependent. There is no universal solution.

• In ecologically sensitive areas, avoid the ultraviolet spectrum and adjacent short wavelengths.

• For humans, the spectrum is determined by task.

• CCT does not determine spectrum.

Finally, if you are specifying or assessing lighting in a place where nocturnal or diurnal wildlife or ecology is a concern, you should consider working with a trusted ecologist or zoological researcher to quantify the impact or potential impact of any installation. Just putting lighting at a low light level, using yellow or amber lighting, or adding a dimmer is not enough to say that an installation is ecologically sensitive.

For the same reason that we need an ecologist to help when we are specifying lighting that is sensitive to wildlife and ecology, an educated lighting specifier is needed to determine lighting solutions that satisfy human needs while mitigating negative side effects. ■

Please see the original publication of PORTFOLIO at LEDucaton by designing lighting for more information on this topic from Kate Sweater Hickcox.