Emerging principles for outdoor lighting could help the stars regain lustre in the night sky. The Illuminating Engineering Society (IES), a leading developer of lighting standards, is collaborating with the research and advocacy organization, DarkSky International, in an effort to curb light pollution and promote installations that could also deliver energy savings and improve neighbourly relations.

“Human beings have evolved under a day-night cycle where darkness is just as important as light,” Brian Liebel, chief program officer with DarkSky International, observed during a recent IES-sponsored webinar. “We need to be conscious about how light affects people, flora and fauna and the view of the night sky, and we need to be responsible for what we are doing when introducing lighting that is not natural to the environment at night.”

Light cast in a upward direction is considered to be light pollution, while light that goes beyond the boundaries of the area it is intended to illuminate is defined as light trespass. Paul Mercier, principal of the firm, Lighting Design Innovations, and an international past president of IES, noted that untrained viewers of these effects are often mistaken about the cause.

“Visibility of light source is not glare. The biggest source of light pollution is reflected light,” he said.

It’s estimated that 83 per cent of the global population lives under a light-polluted sky and an even larger quotient of North Americans and Europeans cannot easily see the stars. Nighttime lighting can disrupt human and animal sleep patterns, divert navigation of birds and fish, and affect the flowering of plants with associated consequences for pollinators. It often trespasses across property boundaries, causing annoyance to those who do not need it, and is a significant electricity consumer, contributing to indirect greenhouse gas (GHG) emissions in jurisdictions with fossil fuel powered grids.

Guiding principles expected to be integrated into lighting standards

IES and DarkSky International joined forces on the project in 2019 and have since developed five guiding principles for responsible outdoor lighting, which both organizations have adopted. Liebel, who participated in that process in his previous role as director of standards for IES, expects the principles will be integrated into IES standards and that maximum caps on outdoor illumination, which are currently absent from standards, could be added.

The five principles define how light should be applied, but, first, prospective installers should consider whether nighttime lighting is even necessary. The underpinning philosophy calls on designers, property owners, business operators and regulators to restrict lighting to: areas where it is needed; during the time it is needed; and in the amount that is needed. The guidance is meant to help users identify those parameters and then sensitively implement required lighting.

“Basically, responsible outdoor lighting is useful, targeted, low-level, controlled and warm coloured,” Liebel advised. “To begin, if a light doesn’t have a use then there’s no point having it there. Be conscious about that; think about that.”

If needed, light should be scoped as much as possible to the tasks that require it; it should be triggered with sensors or moderated with dimmers where possible; and it should not exceed the level that IES standards recommend. Warm colours in the red, orange and yellow wave lengths are a lesser factor in light pollution than blue, which is to be avoided unless it is required for a specific purpose or circumstance.

“Shorter wave lengths of blue are the ones that scatter in the sky and cause more sky glow. They are also the wavelengths that are principally involved with circadian entrainment,” Liebel said. However, he characterized the principles as a package of tactics that can be applied in various combinations to suit site-specific needs.

“If we target light, keep it at the lower level and control it, we’re 90 per cent to where we need to be so spectrum may not have as much of an effect,” he added. “In cases where we can’t do one of these things, spectrum may have more of an impact.”

Curbing light pollution and saving energy are mutually supportive objectives

Bringing a designer’s perspective to the discussion, Mercier talked about navigating lighting ordinances and other planning controls, and the role lighting professionals can play in helping both property owners and local officials work through the technical nuances. He also pointed to some key concepts and instrumental products in responsible nighttime lighting.

Local ordinances are generally tied to at least one of three objectives — reducing energy use; mitigating light pollution; or establishing a design aesthetic — which can be mutually supportive. Mercier suggested that’s particularly the case with the first two goals, but also cautioned that drafters and interpreters of ordinances aren’t necessarily well versed in lighting theory or aware that some stipulations could actually be undermining the outcomes they’re seeking. Criteria for pole heights can be one such example.

“If you control wasted energy, you’re going to do a pretty good job of reducing the amount of light pollution and light trespass in the environment,” Mercier maintained. “Pole heights, in general, are a little suspect whether they help or hurt light trespass. At 20 feet (tall) you’re going to get less reflected light going into the sky because almost all light fixtures that are manufactured these days throw light downwards.”

Similarly, he cited an example of a local prohibition on laser lighting, counterproductively hindering opportunities to take advantage of recent product advancements. “Laser lighting is available as an architectural-style product that has the narrowest beam possible, the best control beam and it shoots light at long distance at a very low wattage. It is the best product for dark sky because it only hits what we’re trying to light,” Mercier reported.

Proponents of the principles for responsible outdoor lighting foresee that they could help fill in the knowledge gap around light pollution and trespass. DarkSky International is already recognized for its certification program for commercial lighting, and it is now  promoting the principles through a wide network of connections.

“In the policies that we’re working on and will be advocating, we’re working towards developing concise language with obtainable outcomes and practical implementation so that it will be easier for cities to adopt ordinances or governments to adopt legislation that can have proven results without over-complicating things,” Liebel affirmed.