Skyglow, light trespass, glare and color remain issues in outdoor lighting design. For the first time, the DesignLights Consortium (DLC) addressed them in technical requirements released December 2021. LUNA version 1.0 identifies outdoor LED luminaires that save energy and promote responsible outdoor lighting.

Skyglow is light emitted or reflected skyward that wastes energy. Light trespass is light that travels into adjacent properties. Glare is improperly controlled high brightness that can impair or disable vision. Together, these issues are sometimes lumped together under the term “light pollution.” In recent years, spectral emission and its impact on circadian health has become another concern, leading the American Medical Association to issue community guidelines recommending 3,000K correlated color temperature (CCT) light sources in 2016.

Many U.S. municipalities have implemented light pollution ordinances. To support governments, the Illuminating Engineering Society (IES) and the International Dark-Sky Association (IDA) developed a Model Lighting Ordinance. In part, it uses the IES’ TM-15 “BUG” method of rating outdoor luminaires for backlight, uplight and glare. The Leadership in Energy and Environmental Design (LEED) building rating system incorporates requirements based on these guidelines. The WELL rating system goes beyond that by including a requirement for 2,700K–3,000K light sources.

Enter the DLC, which represents some 100 utilities and energy-efficiency organizations implementing rebate programs. The DLC maintains several Qualified Products Lists (QPLs), notably a QPL for solid-state lighting (SSL) products, of which nearly half are outdoor LED products. According to rebate fulfillment firm BriteSwitch, 90% of North American energy-efficiency programs require QPL listing as a qualification for rebates, making it influential in the lighting industry.

In recent years, the DLC has included reporting of lighting quality metrics. With LUNA version 1.0, the DLC will offer a new subset within the SSL QPL, identifying outdoor white-light LED products that can earn rebates by satisfying its SSL version 5.1 requirements while satisfying performance criteria designed to minimize light pollution.

“Due to a variety of factors across the lighting market, the unintended consequence of rapidly increasing light pollution has been identified as an issue. The DLC technical requirements have been updated to address lighting quality issues found in both indoor and now outdoor lighting,” said Levin Nock, senior technical manager in networked lighting control for DLC.

Responsible outdoor lighting

Nock said the technical requirements are based on the joint IDA-IES “Five Principles for Responsible Outdoor Lighting.” These principles define responsible lighting as being useful (the light is produced because it is needed), targeted (light is only directed where needed), appropriate (light is not brighter or of a higher level than necessary), controlled (light should only be produced in the amount needed during a given time) and using warmer shades of white light where possible.

While LUNA-qualified products are suitable for virtually all outdoor general lighting applications, they are particularly suited to projects complying with the Model Lighting Ordinance, local ordinances and the LEED and WELL rating systems.

Theoretically, LEDs fit well into best practices. Because LEDs are so small and emit little heat, the light emission is more easily controlled than with traditional lamps, resulting in a potential for greater uniformity of light distribution and the ability to place light precisely (and only) where it is needed.

The early years of LED efficacy saw a wide divide in efficacy between warm and cool color temperatures, but the efficacy of warmer-color LEDs has increased to make it viable. And LEDs are highly controllable, enabling switching and dimming control.

In short, products that live up to the IDA-IES principles are widely available. A significant contribution of LUNA will be as a tool that recognizes these products for rebate programs and discerning specifiers. Beyond that, Nock said he expects the LUNA specification, which began accepting applications for listing in late March 2022, will have significant impact on the marketplace.

The DLC expects a broader selection of qualified outdoor luminaires, including decorative roadway and area luminaires with low uplight, low-CCT luminaires with high efficacy, shielded products and bollards. LUNA may also encourage more public sharing of luminaire spectral data and more efforts to standardize specifications for amber and low-CCT white spectra.

“Most DLC-qualified roadway and area luminaires already have an uplight rating of U0 or U1, and many have a family member available at 3,000K CCT,” Nock said. “The biggest stretch will be optical limitations in decorative products and for bollards, even with the new LUNA efficacy allowance for bollards. The biggest opportunity is likely to be newly qualified products at the lowest white-light CCTs.”

Used as a tool in good design, LUNA-qualified products can help municipalities and organizations achieve more responsible nighttime illumination. These products can be identified on the SSL QPL at DesignLights.org.

Header image by Shutterstock / Romakoma.