Category: Craig’s Lighting Articles

Library Stack Lighting 101

This article describes considerations and techniques for designing book stack lighting, based on the Illuminating Engineering Society’s (IES) RP-4-13, Recommended Practice for Library Lighting.

Below is an application story I contributed to the February issue of tED Magazine. Reprinted with permission.

According to the American Library Association, there are nearly 120,000 libraries in the United States, including school (82 percent), public (8 percent), and other (10 percent) libraries. These buildings feature a variety of spaces and tasks as use of their use has changed. Today’s libraries offer books and artifacts, digital content, computer and Internet access, wireless communications, and a place to meet. A variety of spaces impose common and particular lighting requirements, including entrances, lobbies, retail, office, display, services, multipurpose rooms, and exterior areas.

As library usage shifts to e-books, Internet, and digital content, there is less demand for publicly accessible storage areas. Nonetheless, the most popular type of space remains storage of book collections, called the library or book stack. In typical school and public libraries, this storage takes up 30 to 50 percent of usable floorspace, even more in other library types.

This article describes considerations and techniques for designing book stack lighting, based on the Illuminating Engineering Society’s (IES) RP-4-13, Recommended Practice for Library Lighting.

The library stack

A library stack is a collection storage as opposed to a reading area. In these areas, books are typically stored in shelving units that are often 3 feet wide, 1 foot deep, and 3 to 7.5 feet tall, according to IES. These shelving units connect to form ranges, separated by aisles that are at least 3 feet wide for browsing and 44 inches wide for major circulation and egress paths.

Typically, shelving is vertical, though angled shelves, carrousels, bins, and drawers may be in use for special materials and presentation of books. For older or lesser-used materials storage, high-density storage systems such as rolling stack shelving may be used, in which shelving units rest adjoined and are separated via a floor or ceiling rail using a manual or mechanical method. If rare books and artifacts are stored, these materials may be sensitive to ultraviolet energy and heat produced by electric light and daylight sources, and therefore may need to be isolated.

Image courtesy of Eaton Corporation.

Lighting considerations

In the stack area, the two primary tasks are reading covers and spines on the shelves, requiring vertical illumination from as tall as 90 inches to as low as six inches off the floor; and reading selected materials, requiring horizontal illumination. IES recommends a minimum of about 10 to 40 footcandles of horizontal illumination on the floor and an average of about 15 to 60 footcandles 2.5 feet above the finished floor. IES further recommends about an average 10 to 40 footcandles of vertical illumination on the front face of the shelving 2.5 feet above the finished floor, with a minimum of about half that near the bottom of the shelving. The most desirable light level within these ranges depends on the predominant ages of users, as older people need more light. Regardless, the average-to-minimum vertical and horizontal light level uniformity should be at a 2:1 ratio. High-density book shelving and periodical shelving have similar light level recommendations; consult IES-RP-4-13 to learn more. For high-density book shelving, vacancy sensors can be used to reduce light levels (and save energy) during periods of vacancy during operating hours.

Book spines are typically darker color, resulting in IES estimating an overall reflectance in the aisle of 30 percent or less. As darker materials absorb light, this means a significant amount of light may be absorbed between the top and the bottom of the shelf. Some books are protected by glossy plastic covers, which reflect light and may create a veiling reflection (reflected light that obscures seeing the task) depending on the viewing angle.

Lighting design options

One of the most informative features of IES-RP-4-13 is a stack lighting matrix, which describes lighting design options based on ceiling and shelving height, along with advantages, disadvantages, and design considerations for each.

The options for lower ceiling heights (14 ft.), IES identifies two options, either shelving-mounted direct/indirect or a combination of shelving-mounted direct with ceiling-mounted direct or indirect luminaires.

Image courtesy of Eaton Corporation.

Below, three options for 9- to 14-foot ceilings are summarized:

• Suitable for 3- to 7.5-foot-tall shelving, suspended direct/indirect luminaires, mounted perpendicular to the shelving units, can provide good vertical lighting in the aisles while producing ambient room lighting. Lighting uniformity is improved, and luminaire spacing can be maximized. However, installing these luminaires in continuous rows may result in relatively high lighting power. The direct light component may be shielded to reduce direct glare, while wide direct distribution will improve light level uniformity.
• Suitable for 3- to 7.5-foot-tall shelving, suspended indirect luminaires, mounted perpendicular or parallel to the shelving, can eliminate glare while producing soft ambient lighting. However, as with direct/indirect, mounting in continuous rows may result in higher lighting power. This option is well suited when flexibility is required for future reconfiguration of the shelving layout, or when a reading zone is integrated into the stack area. The luminaires should be mounted as low as possible to maximize the uniformity of illumination on the ceiling and shelves.
• Suitable for 5.5- to 7.5-foot-tall shelving, direct/indirect luminaires mounted on the shelving can provide good vertical lighting in the aisles while eliminating dark areas and producing ambient room lighting. Locating continuous rows on each side of the range may demand more lighting power, and additional lighting may be needed in circulation aisles. Electrical distribution must be provided from the floor to the lighting, which requires coordination and may limit shelving placement.

As with any other lighting application, finding the right stack lighting option requires careful matching to the project characteristics and goals.

Library lighting

Libraries may be changing with the times, but their core role in communities remains the same—providing centers for arts, learning, community-building, and imagination. Using recommended practice, distributors can support their customers in recommending appropriate solutions for their projects.

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T8 Rules to Take Effect

In 2015, the U.S. Department of Energy (DOE) issued new energy standards for general-service fluorescent lamps. These standards identify categories of lamps and impose minimum efficacies, expressed in lumens/W. Primarily impacting 4-ft. 32W T8 lamps and some reduced-wattage T8 lamps, the new standards are now set to take effect January 26, 2018.

Below is my contribution to the January 2018 issue of ELECTRICAL CONTRACTOR.

In 2015, the U.S. Department of Energy (DOE) issued new energy standards for general-service fluorescent lamps. These standards identify categories of lamps and impose minimum efficacies, expressed in lumens/W. Primarily impacting 4-ft. 32W T8 lamps and some reduced-wattage T8 lamps, the new standards are now set to take effect January 26, 2018.

The Energy Policy Act of 1992 regulated general-service fluorescent lamps and granted DOE rule-making authority. In 2009, DOE expanded coverage to include 8-ft. T8 and 4-ft. T5 lamps as well as a broader range of wattages of 4-ft. T8 and T12 lamps. Effective July 2012, these rules eliminated a majority of T12 lamps. Lower-color rendering (700 series) 4-ft. T8 lamps also did not comply, but DOE granted a two-year exemption to manufacturers that requested it.

The 2015 rules tightened existing energy standards for 4-ft. linear T8, 2-ft. U-bend T8, 4-ft. linear T5, and 4-ft. linear T5HO lamps. Minimum required efficacy for T8 lamps increased one to four percent, a modest increase but up to the maximum technology level. Minimum required efficacy for T5 lamps increased seven to 10+ percent. Eight-foot lamps saw no increase. DOE extended the range of covered wattages for 8-ft. single-pin lamps and 4-ft. T5 and T5HO lamps.

Existing exemptions will continue to apply, including 1) lamps designed to promote plant growth, 2) lamps designed specifically for cold-temperature applications, 3) colored lamps, 4) impact-resistant lamps, 5), reflectorized or aperture lamps, 6) lamps designed for reprographic applications, 7) UV lamps, and 8) lamps with a CRI of 87 or higher.

The regulations provided a three-year window for manufacturers to evaluate their products and either discontinue or reengineer them to comply. Eliminations were expected, which may affect lamp availability and cost, though popular models may continue to be available. After January 26, distributors may continue to sell lamps manufactured or imported before that date until inventories are exhausted.

Four-foot linear T8 lamps: At the time of regulation, a majority of these lamps passed the new standards. These were primarily 25W, 28W, and 30W lamps, however; basic-grade 32W T8 lamps did not comply and would need to be redesigned or discontinued. Similarly, 32W lamps designed to offer extended life. Lamps with lower color temperatures were disproportionately affected.

If the installation uses continuous-dimming ballasts, the end-user will have to determine whether the ballasts are rated for reduced-wattage lamps. Operating reduced-wattage lamps on incompatible dimming ballasts will produce unsatisfactory performance. If the ballasts are not rated for reduced-wattage lamps, the end-user must replace the lamps with compliant full-wattage lamps or replace the dimming ballast with ballast rated for reduced-wattage lamps.

Two-foot U-bend T8 lamps: As with 4-ft. linear T8 lamps, a majority initially complied with the new standards, though again these are low-wattage models. Many 32W models did not comply and would be discontinued or reengineered. It is expected that popular 32W models will continue to be available.

An issue with substitution centers on whether the lamp has 1-5/8-in. or 6-in. leg spacing. A majority of users of 6-in. leg spacing use full-wattage lamps on control systems so they can be dimmed, while users of lamps with 1-5/8-in. spacing use reduced-wattage lamps.

Four-foot T5 and T5HO lamps: A majority of 4-ft. T5 and T5HO lamps comply. At the time the regulations were announced, major manufacturers expected that their existing product lines would satisfy the energy standards with limited reengineering, resulting in a minimal impact on availability.

In 2010, DOE estimated that 20 percent of all commercial building sector lamps and 44 percent of industrial sector lamps were 4-ft. T8, representing some 532 million 4-ft. linear T8 lamps and 14 million T8 U-bend lamps. In its justification for the new standards, DOE estimated that over the next 30 years, end-users would receive an average payback of 3-4 years and cost savings with a cumulative new present value (factoring energy cost savings and higher purchase cost) of $2-5 billion based on a respective discount rate of seven and 3.3 percent.

Energy savings are only gained, however, if the end-user switches from a full-wattage T8 to a reduced-wattage T8 lamp or operates a compliant full-wattage T8 lamp on dimming controls. Alternately, they may make the switch to LED to achieve higher energy savings and potentially increased capabilities. Options include LED replacement lamps, retrofit kits, and new luminaires.

Overall, the 2015 rules represent another regulatory step in removing the least-efficient and lowest-cost lamps from the market. Electrical contractors may benefit from consulting with lamp manufacturers about availability and advising their customers about the regulations and impact on their lighting systems.

End-users, meanwhile, should consider the benefits of a comprehensive upgrade rather than replacing non-compliant lamps individually as part of maintenance. A comprehensive upgrade can ensure lighting quality is maintained or improved, reduce the risk of matching incompatible components, and consider all options, such as LED and advanced controls.

For more information, contact the lamp manufacturers.

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DOE Publishes New Lighting Market Characterization

In November 2017, the U.S. Department of Energy (DoE) released its new 2015 U.S. Lighting Characterization report. The 135-page report, which follows similar reports issued in 2001 and 2010, estimates the total installed lighting stock in the United States by light source and building sector. Dense with tables and graphs, it provides data useful for business planning while clarifying trends.

Below is a recent contribution to tED Magazine. Reprinted with permission.

In November 2017, the U.S. Department of Energy (DoE) released its new 2015 U.S. Lighting Characterization report. The 135-page report, which follows similar reports issued in 2001 and 2010, estimates the total installed lighting stock in the United States by light source and building sector. Dense with tables and graphs, it provides data useful for business planning while clarifying trends.

In 2015, lighting consumed 17 percent of all energy used in the United States. Accounting for 37 percent of energy, the commercial sector was the biggest lighting energy user, followed by outdoor and residential. The residential sector, however, had the most lamps—an estimated 6.2 billion out of a total of 8.7 billion, or 71 percent. Most of the lighting stock added since 2010 was in this sector. At 2.1 billion lamps, the commercial sector ranked second (24 percent).

The report confirms and helps quantify several significant trends recognized in the lighting market during the time period:

LED enjoyed rapid growth.
LED penetration increased from nearly 70 million lamps, or 1 percent of the lighting stock, to about 700 million lamps, or 8 percent, in 2015. Adoption was greatest in the outdoor sector (23 percent), followed by the commercial (10 percent), residential (7 percent), and industrial (4 percent) sectors. This trend is currently accelerating.

Incandescent lamps declined. Obsolescent, highly regulated incandescent lamps declined from 45 percent of the total lighting stock in 2010 to 25 percent in 2015. The installed base of incandescent lamps declined 40 percent.

Halogen enjoyed big growth.
While overall, traditional technologies saw little growth in installations from 2010 to 2015, halogen got a big boost by offering a compliant alternative to incandescent general-service A-lamps being phased out. Halogen’s share of the installed lighting stock increased from 4 percent in 2010 to 12 percent in 2015, with installations increasing from 28 million to 693 million, an increase of 350 percent.

Linear fluorescent saw flat growth.
While compact fluorescent lamps increased from 19 to 26 percent of the lighting stock from 2010 to 2015, linear fluorescent stayed at about 2.3 billion lamps, with various winners and losers among the category’s subgroups. Four-foot T8 lamps, for example, gained 38 percent, while obsolete, highly regulated 4-ft. T12 lamps declined 30 percent.

HID saw flat growth. HID lamps also stayed at about 140 million lamps. Metal halide was the sole winner, increasing 11 percent, while high- and low-pressure sodium suffered small declines. The installed base of obsolete, highly regulated mercury vapor lamps, meanwhile, declined 68 percent.

Efficiency is increasing. The net effect of all this was steadily growing average lighting efficacy. National average lighting efficacy increased from 39 to 51 lumens/W between 2010 and 2015. From 21 to 28 lumens/W in the residential sector, 62 to 86 in commercial, 78 to 90 in industrial, and 73 to 80 in outdoor.

Lighting controls show modest adoption.
Adoption of lighting controls is about 18 percent in the commercial sector, including occupancy sensors (10 percent), energy management systems (5 percent), multi-strategy systems (1 percent), timer-switches (1 percent), daylight-responsive controls (1 percent), and dimmers (1 percent). In the residential sector, 11 percent of lamps, the majority controlled by dimmers.

Overall, the report indicates that between 2010 and 2015, lighting in the United States underwent a phase in an ongoing major technological shift to highly energy-efficient light sources, with accelerating emphasis on LED. To get the full report, available as both a PDF and XLS spreadsheet, click here.

Inventory, energy consumption, and lumen production in 2015 by building sector. Image courtesy of the U.S. Department of Energy.

Average lighting efficacy by building sector for 2001, 2010, and 2015. Image courtesy of the U.S. Department of Energy.

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Speech-Controlled Lighting

Virtual personal assistants use speech recognition technology to execute voice commands by users. Now homeowners can control their lighting, shades, thermostats, A/V, and other smart devices using virtual assistant apps and devices compatible with popular smart lighting and home automation systems.

Below is my contribution to the January 2018 issue of tED Magazine, the official publication of the NAED. Reprinted with permission.

Virtual personal assistants use speech recognition technology to execute voice commands by users. By 2021, 1.8 billion users around the world are projected to use virtual assistants, according to market research firm Tractica. While industrial/commercial applications are growing, a major end-use is residential.

In the home, virtual assistants can provide a wide range of services, such as looking up information on the Internet, playing music and videos, and buying products from online retailers such as Amazon. The most popular platforms are Apple’s Siri, Google Assistant, Amazon Alexa, and Microsoft Cortana, with Facebook M launching in mid-2017.

Now homeowners can control their lighting, shades, thermostats, A/V, and other smart devices using virtual assistant apps and devices compatible with popular smart lighting and home automation systems.

A typical solution utilizes a voice-recognizing virtual assistant device (speaker or phone), Wi-Fi connection, downloadable smart device app, and a compatible lighting control or home automation system. Smart lighting systems are typically plug and play, with simple installation and scalability.

“Until recently, controlling smart lighting in the home boiled down to basic apps and automation,” said Greg Rhoades, Director of Marketing, Leviton Energy Management Controls & Automation. “For example, you schedule a lamp to turn ON at sunset, or you use your phone to turn a lamp OFF after you’ve climbed into bed. Now, technology and advancements have allowed us to control our lights through voice command. Quick, easy, and familiar.”

Incorporating voice recognition with a home lighting system begins with selecting a system that recognizes inputs from, for example, Amazon Alexa (with an Echo device), Apple Siri (with HomeKit), Google Assistant (with Google Home), and/or Microsoft Cortana (with Harman Kardon Invoke).

“Manufacturers have different flavors of lighting and home automation systems, but the great thing with speech-recognition technology is that it’s hardware-agnostic,” said Mark Moody, Product Manager, Vantage Controls, Legrand. “There’s not much difference. These virtual personal assistant speakers are able to control many smart home devices from different manufacturers.”

After installation, the user can use the device to tell the lights what to do, providing a convenient input in addition to any others installed in the home, such as keypads, mobile apps, motion sensors, and other systems. When a user issues a voice command, it travels to a cloud-based service outside the home, which then communicates to the control provider’s cloud service via an application programming interface. The control provider’s cloud service then signals the in-home controller to execute the command. An advantage for lighting control is response is virtually immediate.

Michael Smith, Vice President of Sales for Lutron Electronics (, said voice integration can dramatically simplify daily routines. “For example, if you walk into the house and you’re juggling kids, packages, and pets, you can adjust the lights with the sound of your voice by simply telling Alexa, ‘I’m home,’” he said. “Or when you’re easing into the weekend, a quick voice command such as, ‘Alexa, turn on Relax,’ will adjust lights, shades, and temperature and start your favorite music to create the perfect mood for catching up on email or reading the news.”

Besides tech-savvy owners, another good market for this technology, Smith pointed out, is people with limited mobility and/or the elderly. Using voice control enables greater freedom and can have a big impact on maintaining an independent lifestyle.

For distributors, they gain an important selling feature for smart lighting systems. “There is an opportunity for electrical contractors and distributors to extend their range of services and become smart home technology advisers,” said Michael Deschamps, Product Marketing Manager, Philips Hue, Philips Lighting US ( “While installation is simple, many consumers are still looking for support with fixture installs and want assurance that everything will work properly within their homes. It’s important that they learn how everything communicates and what products are interoperable to ensure the best smart lighting and smart home experience.”

Image courtesy of Philips Lighting.

Sample solutions

Leviton’s solutions include Decora Smart lighting controls, a system of switches, dimmers, and plug-in modules for appliances and lamps. Decora Smart with Wi-Fi Technology provides hub-less operation, time-based schedules, If This, Then That customization, free remote control from anywhere, and optional integrated voice control via the My Leviton app, which is compatible with Amazon Alexa and Google Assistant. Decora Smart with HomeKit Technology allows for customizable, hub-less lighting control using an iPhone, iPad, iPod Touch, Apple Watch, or Siri.

“The market potential is unbelievable,” Rhoades said. “Voice controls, now that they’re sprinkled throughout all our homes, purses, and pockets, are driving unparalleled demand for third-party services and products, especially smart home.”

Lutron’s smart wireless lighting and shading control systems include Caséta Wireless, RA 2 Select, RadioRA2, and HomeWorks QS. Systems differ in size, functionality, and skill levels for installation, but all are app-based, work with complementary smart home products such as thermostats, and are compatible with popular voice assistants.

“Smart home products are becoming more mainstream every day—they’re also becoming more affordable and easier to maintain,” said Smith. “Lutron’s message to the electrical industry is, ‘Don’t get left behind.’ Anticipate your customers’ needs and help them get started with a smart home.”

Philips Lighting’s Hue system is based on smart lights (color-tuning lamps, strips, luminaires, and controls), an app, and a bridge that works with Zigbee to connect up to 50 light points and 12 accessories. The system is interoperable with more than 600 apps, products, and platforms from other brands and developers. In addition to voice, Philips Hue smart lighting works with Nest, Samsung Smart Things, Vivint Smart Home, Xfinity Home, and other products for a seamless home automation experience.

“Smart lighting is a great place to start when building a smart home,” Deschamps said. “You can see and feel its impact on your home and life immediately.”

Image courtesy of Philips Lighting.

Final word

Moody advised contractors and distributors to keep it simple. “The common pitfalls are a poor network and overcomplicating the system, from commands to integration and configuration,” he said. “The network needs to be robust. Electrical contractors also need to be aware of the added programming and configuration that will go into custom skill environments for voice control. Keep it simple.”

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Lighting—the Next iPhone?

At the Strategies in Light conference held February 28-March 2, 2017 in Anaheim, California, Dan Ryan, VP Product, IoT Solutions, Acuity Brands Lighting examined lighting disruption posed by LED technology and the Internet of Things (IoT). He said a good starting point to predicting what will happen next in the lighting industry is to look at changes in similar industries such as electronics and computing. Specifically, by examining bundling and unbundling, based on a quote attributed to American executive Jim Barksdale: “There are two ways to make money in business: You can unbundle, or you can bundle.”

Below is another article I contributed to the December 2017 issue of ELECTRICAL CONTRACTOR.

At the Strategies in Light conference held February 28-March 2, 2017 in Anaheim, California, Dan Ryan, VP Product, IoT Solutions, Acuity Brands Lighting examined lighting disruption posed by LED technology and the Internet of Things (IoT). He said a good starting point to predicting what will happen next in the lighting industry is to look at changes in similar industries such as electronics and computing. Specifically, by examining bundling and unbundling, based on a quote attributed to American executive Jim Barksdale: “There are two ways to make money in business: You can unbundle, or you can bundle.”

Bundling, Ryan explained, is when products are integrated and sold as a package instead of separately. He cited numerous examples in the computing and consumer electronics industries. In computing, for example, almost every big tech change saw a bundle or unbundle event. In the pre-Internet era, Microsoft dominated by bundling all applications into Windows. Then the Internet unbundled everything until Google, Facebook, Amazon, Apple and others began to rebundle everything again. Currently, elements of these devices and services are being unbundled as individual products such as Amazon’s Echo and Google Home voice-assistant devices. Ryan said another major unbundling event might soon occur with cryptocurrencies such as bitcoins and blockchains, the digital ledgers that manage these currencies.

“The basic aspect is that there are powerful economic forces in play that benefit both buyers and sellers,” Ryan said about bundling. “Buyers get access to more services for a lower cost than they would if they purchased independently, and sellers gain more profits by selling to a larger customer base. Right now, the lighting industry is going through a bundling phase, where IoT services as well as building management systems are bundling with lighting projects.”

He added lighting might be considered the new iPhone, a classic example of bundling in the consumer electronics industry. Today’s iPhone integrates functionality into a single pocket device that 15 years ago would have required numerous larger devices—video player, camera, video camera, telephone, CD player, TV, laptop. In lighting, Ryan said, lighting is in a unique position to serve as an aggregation point for the delivery of both light and IoT services.

“Much like that closet full of consumer electronics that’s now bundled into an iPhone, we’re seeing a bunch of systems that used to be sold, installed and maintained separately start to consolidate into a single platform—smart lighting,” Ryan said. “We’re seeing lighting companies bundle new digital services with lighting with offers like indoor positioning, asset tracking and occupancy analytics. The common pattern with solutions is leveraging the lighting network to collect data about the environment and then using that data to improve a business process.”

Ryan said that while bundling will likely remain a driving force in the lighting industry for the foreseeable future, unbundling is likely to occur again. The key is standardization enabling compatibility, which drives competition and development of a new services layer. An open question is whether the LED luminaire, which bundled the light source with other components, will unbundle to allow servicing of interchangeable components using standard connections.

The biggest impact of these events is not necessarily to product but often to their supply chains. As an example, Ryan pointed to the impact of Internet video streaming had on the cable TV industry. Consumers are no longer limited to getting content through a bundle offered by a sole provider but can subscribe to video content services from numerous Internet sources such as Netflix and Hulu. In lighting, Ryan believes true disruption is not occurring, as how lighting projects are specified and sold is not materially changing. While distributors may see maintenance, repair and operations (MRO) sales decline due to the longevity of installed LED sources, they may also benefit from the current bundling trend due to larger project sizes involving higher-end systems. Similarly, as long as projects are specified and sold the same way, the role of the contractor will remain the same, though these systems may present complexity challenges and a learning curve, at least in the short term.

“I don’t think contractors need to become experts in IoT services to still play the important role they play in the channel today, nor should we expect them to,” said Ryan. “Intelligent lighting systems need to be simple to install, commission and maintain. If deploying a lighting-based IoT network becomes as costly as maintaining an independent network, then why bundle at all?”

He said a wildcard in the market is low-voltage DC lighting control solutions like Power over Ethernet (PoE) systems, which are gaining momentum in the new construction market. Ryan pointed out this allows contractors to tap into a different labor pool for executing projects.

“The point here is that by moving into an entry point for IoT, the total available market opportunity for the entire industry is going to increase, which will benefit multiple players in the channel,” Ryan said.

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Circadian Lighting: New Research and Tools

The lighting industry continues to explore potential benefits of lighting solutions that optimize human health. Studies indicate light has physiological effects that go beyond vision. In recent years, the industry has focused on the impact of light on the human circadian system, and how electric lighting choices thereby can affect circadian health. Mariana G. Figueiro, PhD, Professor and Light and Health Program Director at the Lighting Research Center at Rensselaer Polytechnic Institute, says there are four major factors in designing a lighting solution that optimizes circadian health.

Below is my contribution to the December 2017 issue of ELECTRICAL CONTRACTOR.

The lighting industry continues to explore potential benefits of lighting solutions that optimize human health. Studies indicate light has physiological effects that go beyond vision.

In recent years, the industry has focused on the impact of light on the human circadian system, and how electric lighting choices thereby can affect circadian health.

The circadian system is very important. This system produces and regulates bodily functions based on 24-hour cycles, or circadian rhythms. A big example is the sleep-wake cycle. Disrupting circadian rhythms can contribute to poor nighttime sleep, increased daytime napping, and greater risk of depression, obesity, diabetes and seasonal affective disorder.

The daily change from light to dark is the primary stimulus for synchronizing circadian rhythms to our location. The human eye has cells that are receptive to light and that connect directly to the brain’s master clock, converting light into neural signals that regulate circadian rhythms. For millions of years, the sunrise-sunset cycle performed this job, but in the modern era, we rely on electric lighting systems.

Traditionally, these lighting systems are designed for vision, disregarding light’s non-visual impact. Mariana G. Figueiro, PhD, Professor and Light and Health Program Director at the Lighting Research Center at Rensselaer Polytechnic Institute, says there are four major factors in designing a lighting solution that optimizes circadian health.

First and foremost is intensity, or the quantity of light falling on the eye’s photoreceptors during the day. What’s important here is light at the plane of the cornea or eye, not light falling on the horizontal workplane. Next is spectral power distribution (SPD)—the combination of wavelengths of light being emitted by the light source. Circadian regulation is most responsive to short-wavelength light (460 nm, or “blue”). (Note SPD and correlated color temperature, or CCT, roughly correlate but not exactly; request SPD data for a light source, not just CCT.) Meanwhile, longer-wavelength light (“red”) can also produce an alerting effect. Finally, timing, duration and photic history are also important—when the light is received, how much light cumulatively falls on the eye throughout the day, and previous light exposure.

A circadian lighting solution, therefore, ideally exposes occupants to high-intensity light (at least 20-40 footcandles at eye level) in the morning, which can be enhanced with short-wavelength light. Daylight is ideal. Otherwise, electric direct-indirect general lighting, task lighting, luminous workstation partitions (see Figure 1 for example), and wall lighting can increase vertical light levels. Controls can play an important role in adjusting light levels and spectrum throughout the day. Meanwhile, as an aside, steps should be taken to minimize glare and objectionable flicker.

Due to differences in human physiology, one’s mileage may vary. Studies tend to suggest outcomes for average populations under certain conditions. Lifestyle is a major determinant, along with evening and nighttime lighting. Overall, circadian health is a puzzle. For commercial buildings, designers may choose to ensure their piece is optimized.

“Architectural lighting isn’t just for vision anymore,” Figueiro says. “Clients are increasingly requesting and expecting lighting systems and applications that can support human health and wellbeing.”

She says if a company wants to attract and retain top talent in today’s labor market, the office environment must be designed with employee needs and desires at the forefront. Beyond that, companies that care about the health and wellbeing of their workforce should consider healthy lighting.

“People are the most important asset of an organization,” says Figueiro. “Why not provide them with the best lighting? Providing occupants with proper circadian lighting is similar to providing them with ergonomic chairs or flat screen computer monitors.”

For lighting professionals, this emerging lighting trend poses several challenges. For starters, achieving circadian response with a vertical light level of 20-40 footcandles (fc) translates to roughly 80-120 horizontal fc, which prevailing commercial building energy codes do not support.

Tunable-white LED lighting can play an important role here. It can adjust spectral emission to emphasize short-wavelength light, which can increase circadian response by a factor of two to three. Figueiro found that when targeting 30 fc on the horizontal workplane, circadian stimulus required an SPD emitting more short-wavelength light (6000K correlated color temperature, or CCT). At 40 fc, an SPD emitting less short-wavelength light (4500K CCT).

“In situations where renovations may be impossible due to budgetary or architectural constraints, low-cost and low-impact light oases can be established,” Figueiro notes. (See Figure 2 for example.) “Such oases can be quite effective when occupants are provided with information on light therapy and the health value of circadian stimulus, and can be tailored for limited spaces ranging from small offices to submarines.”

Lighting professionals are also seeking further research confirming positive outcomes for circadian lighting, along with tools and metrics they can use to evaluate, compare and implement solutions. The Lighting Research Center recently published the results of an office circadian lighting research project and a circadian stimulus metric and predictive tool.

“Much has been learned over the past decade about the impact of light on circadian rhythms, and interest in the topic of light and health is certainly on the rise,” Figueiro says. “New metrics are now being proposed. But rather than wait until standard-setting bodies agree on new metrics or guidelines, lighting professionals can begin to apply current research to help people live better right now.”

Luminous partitions can help increase the quantity of light falling on the eye, potentially producing a circadian response. Image courtesy of the Lighting Research Center.

CS metric and calculator

As a design objective, circadian light stimulation differs from achieving sufficient functional illumination for visual acuity and safety, requiring a new metric. The LRC developed the circadian stimulus (CS) metric as a proposed basis for evaluation, comparison and application of circadian lighting solutions. Validated in controlled experiments, CS is based on an LRC model of how the retina converts light stimulation into neural signals, focusing on the quantity of circadian-effective light falling on the eye’s cornea.

As manufacturer claims about circadian benefits have begun to proliferate, proposed metrics such as CS can be very helpful. The CS metric has been successfully used in field applications, including persons with Alzheimer’s disease and U.S. Navy submariners.

Exposure to a CS of 0.3+ at the eye for at least one hour in the early part of the day is considered effective for circadian stimulation. Circadian response activates at a CS of 0.1 and caps at a saturation point of 0.7.

“Although responses to circadian-effective light vary from person to person, a lighting system that delivers a circadian stimulus greater than 0.3 during the day—particularly in the morning—and less than 0.1 in the evening is a great starting point,” Figueiro says.

Subsequently, the LRC released the CS calculator, a free tool designed to help lighting professionals choose light sources and light levels ideal for circadian stimulus. The lighting professional establishes the base condition using the CS calculator and software such as AGi32. Various lighting strategies are then considered, which can be fine-tuned to achieve the right balance between circadian stimulus, IES recommendations, energy codes and owner requirements. In July, LRC released a new version providing additional functions such as ability to calculate CS levels in rooms with multiple light sources and combine pre-loaded and user-supplied SPDs to create a single CS measurement and single relative SPD. Download the CS tool at

“The CS calculator enables a lighting professional to quickly and easily convert the photopic illuminance provided by any light source at any light level into the effectiveness of that light for stimulating the human circadian system,” Figueiro says. “It helps one compare effectiveness of various light sources for the circadian system.”

She points out that while the CS tool is helpful for designers, additional interest is coming from manufacturers. Some may publish CS values in their cut sheets, others develop lighting control schemes around CS.

For renovation projects lacking the budget and flexibility to implement circadian lighting on a large scale, light oases such as this room provide a space where occupants can receive a dose of circadian-responsive light. Image courtesy of the Lighting Research Center.

GSA study

LRC put its ideas to the test in a field study conducted at five office buildings managed by the U.S. General Services Administration, which funded the study. It found that office workers receiving a substantial dose of circadian-effective light in the morning have better sleep and lower levels of depression and stress than workers who spend their mornings in low light levels. GSA intends to use the data from this research to support its efforts in developing new healthy lighting practices at federal buildings.

The study used the Daysimeter, a device LRC developed to measure the amount of circadian stimulus received throughout the day. The 109 study participants wore the device for seven consecutive days in summer and winter months, from 2014 to 2016. The LRC collected data during these periods covering sleep and mood, using five standard questionnaires. The participants also logged bedtimes and wakeup times. Sleep latency, quality of sleep and naps were calculated using Daysimeter data.

The LRC determined that participants receiving a morning electric and/or daylight CS of at least 0.3 displayed greater circadian entrainment than participants receiving a morning CS of 0.15 or lower. They were able to fall asleep faster at bedtime, particularly in winter. They also experienced higher-quality sleep. With no seasonal variation, they reported lower stress levels. Participants receiving lower CS reported taking about 45 minutes to fall asleep at bedtime.

“The results are a first step toward promoting the adoption of new, more meaningful metrics for field research, providing new ways to measure and quantify circadian-effective light,” says Figueiro.

U.S. General Services Administration circadian lighting research project. Image courtesy of the Lighting Research Center.

In the GSA research study, the Lighting Research Center developed workstation task lighting to help control light levels falling on occupant eyes. Image courtesy of the Lighting Research Center.

Final word

Clearly, circadian lighting is a new field, and more work needs to be done in regards to daylight integration, surface characteristics, controls and understanding special populations. Standards and best practices need to be formulated. It’s important to recognize blue light is not the only answer, and not to overstate results and benefits. Successful implementation requires an adequate budget and a high degree of design influence over general lighting, task lighting, controls and potentially daylight, furnishings and finishes.

That being said, Figueiro believes circadian lighting is actionable now and points to fresh research, metrics and tools as ways for lighting professionals to begin exploring opportunities with their projects. As interest in circadian lighting grows, and should that interest translate to owner demand and best practices, it may spark a revolution in lighting design. Lighting that not only provides visual and aesthetic benefits but also supports circadian regulation.

She says, “We strongly encourage lighting professionals to seek opportunities that provide a deep understanding of the many ways light can affect health and wellbeing, and to become adept at addressing and designing lighting for special applications effectively.”

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Creative Destruction in Lighting

At the 2017 Strategies in Light conference, Robert F. Karlicek, Jr. spoke about creative destruction in the lighting industry brought on by LED technology and the Internet of things (IoT). After catching his fascinating presentation, I interviewed him for a story for ELECTRICAL CONTRACTOR. Click here for an excerpt and link where you can read the article.

At the 2017 Strategies in Light conference, Robert F. Karlicek, Jr., spoke about creative destruction in the lighting industry brought on by LED technology and the Internet of things (IoT). Karlicek is a professor and director for the Center for Lighting Enabled Systems and Applications at the Rensselaer Polytechnic Institute, Troy, N.Y.
 After catching his fascinating presentation, I interviewed him for a story for ELECTRICAL CONTRACTOR. Excerpt below:

In 1942, economist Joseph Schumpeter coined the term “creative destruction” to describe the impact of innovation. In the lighting industry, LED technology and integration of IoT services are disrupting traditional lighting and legacy business structures, supply chains and distribution channels.

For the majority of the market, the primary focus is energy efficiency and performance. The high efficiency and longevity of LED products makes them appealing for both new and existing construction. This is destructive to traditional lighting manufacturing and distribution. 

In the specification-grade segment, innovation focuses on adding value—new form factors, features, color tuning, dimming, data production, IoT integration and visual light communication. As color tuning and IoT concepts continue to enter the market, Karlicek believes this segment will grow.

Click here to read more.

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Lighting for Learning

In 2016, education put-in-place construction spending reached $88.7 billion, making it the largest building market. This exciting lighting market is changing as teaching methods evolve toward greater interaction, flexibility, and technological integration. In this article, I talked to manufacturers about how school lighting is changing.

Below is my contribution to the November 2017 issue of tED Magazine, the official publication of the NAED. Reprinted with permission.

Image courtesy of Hubbell Lighting.

In 2016, education put-in-place construction spending reached $88.7 billion, making it the largest building market, according to the U.S. Commerce Department.

“This is an exciting time for the K-12 lighting market,” said Trish Foster, LC, LEED-Green Associate, Director, Education Market Development, Acuity Brands. “From a renovation standpoint, this means older, dated schools are looking not only for more-efficient solutions but also solutions that can have a positive impact on the learning environment.”

The modern classroom is changing to accommodate new teaching methods and technologies. Classrooms are no longer static environments. They are incorporating a range of technologies, from mobile devices and computers to interactive whiteboards and modular furniture. They are becoming more collaborative spaces in which teachers and students interact and exchange ideas in nontraditional ways. If activities and spaces are flexible, the lighting must be flexible as well.

“Video displays, whiteboards on multiple walls, tablets for all students, Wi-Fi in every classroom are some of the things we see in new classrooms,” said Terry Clark, Founder, Finelite. “Since each of these needs a different type of light at different times in different intensities, new lighting systems are needed.”

He described the K-12 education market as “underserved.”

“More attention is given to selecting flooring than the best way to light a classroom,” Clark said. “As a result, too often, lighting has been bought on a lowest first-cost basis. When lowest first cost is the focus, it is difficult for a distributor to add value and make a profit on the project. That is about to change.”

Image courtesy of Finelite.

Lighting change
From LED technology we can gain high energy efficiency and optical control, flexibility with connected controls, ability to adjust color appearance and other capabilities. The latest energy codes encourage LED adoption while requiring a full range of control strategies. The Illuminating Engineering Society’s RP3 document recognizes evolving best practices. And building recognition standards and programs such as the Collaborative for High-Performance Schools (CHPS) promote use of these best practices.

The majority of energy codes require manual control, occupancy/vacancy sensing, and daylight-responsive controls in classrooms. The sensor must automatically turn the lights OFF within 30 minutes of the space being vacated. If the sensor automatically turns the lights ON, it must do so to 50 percent or less of lighting power (bilevel switching). One or more manual switches must be installed at the entrance allowing control of all general lighting; additional switches may be installed as needed. Daylight-responsive controls must be installed where daylight is present and respond via bilevel switching, step dimming, or continuous dimming.

A classroom lighting solution that maximizes CHPS points is energy code-compliant, features daylight and indirect/direct electric lighting, and allows teachers to control the general and separate whiteboard (if present) lighting. The general lighting is controlled in two modes: General (10-30 footcandles in the student zone) or AV (maximum 7 footcandles on the screen). The teacher may also manually override the occupancy sensor time delay during written tests. If daylight-responsive controls are used, the light sensor takes precedence over manual dimming for the upper light level limit.

“The ease of dimming LEDs is a huge advantage,” said Charles Knuffke, Wattstopper Systems VP and Evangelist, Legrand. “Additionally, there is an opportunity to move to shorter time delays when outside normal hours, such as the summer period, since there’s no reduction of product life.”

He added that controls aren’t just for new buildings anymore. “Many classrooms still have no automatic controls,” he pointed out. “These spaces should look at either wireless or simple to install controls that can be retrofitted in easily.”

Knuffke warned that while controls can add utility and energy savings, distributors should favor products that are easy to use and recommend training teachers about how the controls work.

Finelite responded to a DOE RFP to build a lighting and control system that would serve the classroom of the future. The system includes highly efficient tunable-white LED lighting, automatic controls, and a custom teacher interface promoting easy use of teacher controls. Image courtesy of Finelite.

Color control
One of the industry’s latest major product trends is tunable-white lighting, which offers a choice of correlated color temperatures (CCTs) typically from visually warm (low CCT) to visually cool (high CCT). In a classroom, this is typically achieved using a luminaire housing separately controllable warm- and cool-white LED arrays, with the desired CCT achieved via relative dimming between these two primaries.

“The ability to tune the color temperature of the light is certainly one of the most significant advances,” Foster said. “A class with intensive laboratory-style learning may benefit from a different color temperature than a class focusing more on reading or independent studies. With advancements in LED technology and easy-to-use control platforms, every classroom can now benefit from tunable-white lighting.”

She pointed to research suggesting changing CCT based on classroom activity can affect mood, behavior, and concentration. In one study, a fifth-grade classroom in Carrollton, Texas installed tunable-white lighting at the start of the 2016 school year and saw an improvement over the previous year’s scores in the annual state examination.

“The kiddos embrace it,” Foster added. “They remind the teacher to change the lighting when an activity changes. They also learn about the impact of lighting on the space.”

Clark believes efficient, dimmable, and tunable-white LED lighting will serve as an integral part of the classroom of the future. In 2014, Finelite responded to a Department of Energy (DOE) request for proposal to create a robust classroom lighting solution would deliver exceptional lighting quality for very low energy levels. The company built the luminaires, integrated controls, and mocked up a classroom for testing.

Capabilities include controls specifically designed for teachers to control CCT, dimmable sources, centralized building control, energy-code compliant control, plug-and-play installation, and a single source for pricing, shipping, and warranty. All while delivering a substantially lower life-cycle cost.

“The new system goes sufficiently far beyond what is presented in CHPS that the section will need to be substantially updated and the points assigned to better lighting increased significantly,” Clark added. “A new lighting approach is needed for every classroom, and it must be applied across the board—not reserved for only the most affluent school districts.”

Tunable-white lighting offers the ability to change CCT according to classroom activity, such as test taking, calming, and more. Image courtesy of Acuity Brands.

Selling school lighting
Foster advised distributors to think outside the traditional way of selling lighting products. “It is not about the total solution, integrating luminaires and controls,” she said. “Simple energy savings and payback is still important, but the conversation is now expanding into an emotional connection where student performance and optimizing the learning environment is key.”

She added distributors should expand the reach of the conversation to stakeholders who were perhaps not engaged in the past. “It’s now a full circle between facility managers, principals, teachers, and the distributor,” she said.

Knuffke sees distributors in the perfect place to sell lighting to both new and existing construction projects. “Nothing beats having a close relationship with the school facility personnel in the areas they cover, having the ability to educate on new technologies and product innovations, and understanding the local electrical and energy codes,” he said. “Keep educating yourself—distributors that do have a competitive advantage.”

Clark said classroom lighting is a hot market ripe for good selling and upselling opportunities. “Ask great questions,” he advised. “If they are asked to price a retrofit, ask why they are not taking the opportunity to upgrade to a new system. Do not assume the only issue is first purchase price. Strive to add value to the project. No other areas of school design and construction has undergone as much change as the way we should light classrooms. You will bring value to your customers by helping make them aware of this. Bringing increased value to your customers is what you need to continue to succeed in the years to come.”

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Outdoor Lighting 101

Outdoor stationary lighting presents a substantial market and a distinctive subset of lighting design. This article, which I wrote for the November issue of tED Magazine, describes considerations for evaluating and designing outdoor lighting systems.

Below is another article I wrote for the November issue of tED Magazine. Reprinted with permission.

Outdoor stationary lighting presents a substantial market and a distinctive subset of lighting design. While the market covers a variety of applications, the largest are building exterior and area and roadway lighting.

In a typical indoor space lighted during the day, the ceiling is relatively bright, the light is localized and has little or no impact on the natural environment, and the eye uses photopic vision. With outdoor lighting, the “ceiling” is relatively dark, unshielded lighting may be visible at great distances and impact the environment, and the eye may use scotopic vision (dark conditions) or mesopic vision (semi-dark).

Generally, the primary goals are to enable nighttime business, leisure, and enjoyment while promoting safety and security. A key decision is choosing what to light. Good outdoor lighting lights only what is needed without glare, light trespassing onto neighboring properties or negatively impacting wildlife, and uplight that can produce skyglow.

In this article, we will discuss outdoor lighting design considerations and the basic design process. It is based on the Illuminating Engineering Society’s (IES) RP-33-14, Lighting for Exterior Environments and other sources.

Visual factors
Visual factors relevant to outdoor lighting include light level, brightness, visual adaptation, and color quality.

Light level.
Measured in footcandles or lux (metric), light level is the quantity of illumination falling on a specific area. The designer’s aim is to ensure sufficient light output to provide an average or minimum light level over time, which may be defined by the maintenance interval. IES recommends a range of light levels for accent, building entry, facade, fountain, parking deck, parking lot, pedestrian stairs, roadways, outdoor pools and retailing, pedestrian path, and other applications. A second goal is to provide a uniform distribution of light. IES recommends maximum-to-minimum and average-to-minimum light level uniformity ratios.

Brightness. Luminance is the light reflected or emitted to the observer’s eye; brightness is the subjective perception of luminance. Excessive brightness is glare, which may be disabling or discomforting to vision. A bright outdoor luminaire does not equate to sufficient light level.

Visual adaptation.
The eye takes time to adjust from light to dark, including reduced visibility. Good outdoor lighting provides smooth transitions from bright to dark areas. In a large visual environment, very bright areas may result in less visibility in adjacent dim areas within view.

Color quality. At very low light levels, the eye adapts to scotopic vision, which is essentially colorblind, with an exception for very bright objects such as traffic lights. Most urban environments deliver enough ambient light to enable mesopic vision, a combination of photopic (daytime) and scotopic (nighttime) vision. For greater visibility, consider luminaires with some short wavelength (blue) output. Short-wavelength light is more likely to be judged as glaring, however, because the eye is more sensitive to this radiation at low ambient light levels, and short-wavelength light scatters more widely than other wavelengths within the eye. Outdoor luminaires should be selected with an appropriate spectral mix that provides both visibility and visual comfort.

Image courtesy of Wattstopper.

External factors
A variety of external factors influence selection of outdoor lighting, from space use to community master plans to local regulations regarding wildlife. Here, we will focus on three: energy codes, dark-sky ordinances, and American Medical Association (AMA) guidelines.

The latest generation of energy codes and standards prescribe maximum allowable power for outdoor lighting by application. These power densities are declining as more-efficient LED outdoor lighting has become viable. Codes and standards also contain detailed mandatory control requirements.

Dusk-to-dawn lighting must be turned ON/OFF using a photocell. During operation, power must automatically reduce by at least 30 percent after business operations or in response to occupancy. Façade/Landscape lighting must be operated using a combination photocell/time switch that turns it OFF between midnight or business closing (whichever is later) and 6:00AM or business opening (whichever is earlier).

Dark-sky ordinances vary but are generally designed to limit light trespass, skyglow, or both. Light trespass occurs when light spills onto neighboring properties. Skyglow occurs when uplight from nighttime lighting obscures a view of the stars. Many communities have adopted the Model Lighting Ordinance (MLO) developed by the IES and International Dark-Sky Association, which addresses both light trespass and skyglow in addition to energy efficiency and glare.

Both the major energy code standards and the MLO base requirements on a lighting zone (LZ) system (LZ 0-4). These zones range from no ambient light (e.g., wilderness parks and preserves) to high ambient light (e.g., high-activity commercial districts).

In 2016, the AMA issued community guidance cautioning against glare, which can affect safety, and LED lighting with a very cool correlated color temperature (CCT), which may suppress melatonin production. AMA specifically recommended 3000K sources, luminaire design that minimizes glare and light trespass, and dimming during off-peak operation. While cooler CCT sources remain more efficacious (lumens/W) than warmer CCT sources, the efficacy gap has been shrinking, increasing demand for warmer sources. The CCT recommendation received considerable pushback from the lighting industry, including IES, which issued a public statement saying the 3000K recommendation is insufficiently substantiated and that CCT itself is not an appropriate metric for predicting health outcomes.

Product selection factors
A wide variety of factors influence outdoor luminaire selection. Wattage, light output and distribution, glare control, color quality, ruggedness, certifications, aesthetics, maintenance, cost, and others come into play. Due to energy codes, controllability of LED sources, and advances in wireless connectivity, lighting controls are becoming much more important, offering extraordinary possibilities for global management and data collection.

The Backlight Uplight Glare (BUG) luminaire classification system developed by IES in TM-15-11 offers a useful tool for evaluating luminaire quality. Featured in the MLO. BUG delineates a luminaire’s light output by zones and tags these zones by distribution—backlight, which can cause light trespass; uplight, which contributes to skyglow; and glare, which is objectionable light. There are three zonal regions for backlight, for example (high, middle, and low). The MLO establishes maximum zonal lumens for each by LZ. Many luminaire manufacturers publish BUG ratings for their outdoor luminaires, while the MLO provides maximums by LZ.

Putting it together
All of the above must be matched to the application to provide the optimal customer solution. With the proliferation of the LED source, outdoor luminaires now offer much more expansive and robust capabilities, such as superior optical control, dimming, collecting data, and changing color by time of night. By understanding the basics of outdoor lighting, electrical distributors can add even greater value to projects.

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Evaluating Color with LED

LEDs have further differentiated themselves from traditional light sources by offering dramatically expanded color capabilities. These capabilities enable distributors to better serve existing customers and build new markets. Accomplishing this requires understanding LED technology, metrics used to evaluate color, and knowing what the customer wants and needs.

Below is my contribution to the November issue of tED Magazine. Reprinted with permission.

LEDs have further differentiated themselves from traditional light sources by offering dramatically expanded color capabilities. These capabilities enable distributors to better serve existing customers and build new markets. Accomplishing this requires understanding LED technology, metrics used to evaluate color, and knowing what the customer wants and needs.

The LED advantage
Visible light is energy residing along the 400-700 nanometer band of the electromagnetic spectrum. The size of these wavelengths corresponds to specific colors from violet to red. Combining these wavelengths produces white light. Separating them via a prism produces a rainbow.

The eye perceives color in an object because that color is present in both the object and the light striking it. The object absorbs all colors except a given color, which reflects to the eye. While daylight offers a full spectrum source, electric light sources are engineered as mixes of wavelengths at relative intensities, typically focused on red, green, and blue (RGB). The spectral makeup is expressed in the source’s spectral power distribution (SPD).

As with traditional light sources, with LEDs we have a choice of specific colors or white light. In the case of color, this is accomplished with LEDs emitting light in a narrow spectral band. For white light, blue or ultraviolet LEDs coated with a phosphor producing a deep blue peak and high irradiance in the 470-630 nanometer range.

With LEDs, however, colors can be mixed to produce virtually any color needed, allowing dynamic effects. White light color appearance can be adjusted with relative ease using controls. Combining white and color LEDs allows virtually any SPD to be created, opening possibilities in targeting light to human physiology, plant growth, and environmental needs. And with advances in LED technology, building owners no longer have to choose between excellent color quality and high efficiency.

Tunable-white LED lighting, matched with appropriate controls, enable CCT adjustment across a given range to satisfy variable preferences for applications demanding color flexibility. Image courtesy of USAI Lighting.

Color appearance

Manufacturers describe the color quality of light sources using metrics based on standardized measurements. The most popular are correlated color temperature (CCT) and color rendering index (CRI).

Measured in kelvins, CCT is the color appearance of a light source relative to an ideal reference light source. Color appearance is generally classified as visually warm (about <3000K, or yellowish white), neutral (about 3500K, white), or cool (about >4000K, or bluish white). A light source heavily laden in blue and deficient in red wavelengths will saturate blues in the space while muting reds.

A challenge for LEDs is the manufacturing process inherently involves variations in CCT. The result is potential color variation between LED products. To address this issue, manufacturers test and bin their LEDs according to deviation from CCTs based on x, y coordinates on the CIE 1931 Chromaticity Diagram, using a standardized method. The smaller the bin, the tighter the control of color variation, though gaining this consistency may impose a higher cost. Some manufacturers maintain extremely tight deviation as a point of differentiation for their products.

“Color consistency from credible LED manufacturers has improved significantly since white LEDs were first produced,” said Andrew Kites, Global Product Manager, Philips Lighting. “Some manufacturers have gotten much more skilled at producing LEDs that are closer to the center of the ANSI bin for that CCT, reducing waste in manufacturing from out-of-spec product, reducing LED costs, all while improving color consistency.”

Advances in control and driver technology enable manufacturers to provide custom SPD (using RGB+ LEDs), luminaires to produce both high-quality white and color (White+), and designers and users to adjust CCT in the field (White/White+). This extraordinary potential is opening new markets. Additionally, dim-to-warm LED products are growing in popularity for applications where users expect their lighting to dim to a warm glow similar to incandescent.

“It’s always important to listen to the customer,” said Bonnie Littman, President and CEO, USAI Lighting. “The better we can understand their preferences for color, the better we can serve them and provide the right product. There’s no ‘one size fits all’ when it comes to lighting, and there’s no reason someone should be relegated to static white light if that’s not what they want or need.”

She pointed to several examples where coming up with a customer-specific color solution became a point of differentiation for her company. Outdoor lighting on the Gulf Coast that provided nighttime visibility without disrupting the nocturnal habits of sea turtles. Experimentation with different CCTs in classrooms. Optimal SPDs for high-end retail. As the industry’s understanding of light and health develops, this capability may prove integral to circadian lighting, as spectrum is a major factor in circadian response. And some manufacturers are already looking beyond health to well-being, mood, and satisfaction via personalized lighting solutions.

“Research is ongoing to determine the appropriate light levels, spectral content, and lighting design that provides support for human circadian biorhythms,” Kites said. “The research points to humans generally having a biological response to both blue and red wavelengths.”

“With all of the promising LED products on the market now to support circadian health, I see this time as an exciting moment for the lighting industry to have a meaningful impact on workplace and healthcare environments,” Littman noted. “By mimicking the daily color temperature cycle of natural daylight, these technologies we’re creating can help minimize disruptions to the natural circadian rhythm, thus supporting overall health, well-being, and healing.”

Paul Scheidt, Product Marketing Manager, LED Components, Cree, however, says he has not yet seen a product that demonstrates a comprehensive understanding of physiological response to lighting. “The industry is not here yet,” he said. “We have identified the right variables for circadian lighting—color and light amount. However, we do not know where or how you set these controls to create direct biological impact, such as mood and energy levels. No one has a ‘mood’ knob on their light. Today’s controls are color and light amount. As an industry, we are still at the beginning of understanding the notion of mood and human preference for lighting.”

Color rendering and TM-30
While CCT is useful, it does not indicate whether the light source renders colors how most people would expect them to appear. Two sources with the same CCT may render various colors differently due to differing SPDs. A balanced SPD, particularly RGB, generally means the source offers good color rendering. A simpler and more direct way to evaluate color rendering is the lamps CRI rating. If two sources have the same CCT, one can meaningfully compare CRI to choose the right source.

Manufacturers test their sources and calculate CRI based on how closely they render eight standard color samples compared to an ideal reference source with the same CCT. The CRI rating is the average of these values. The less deviation from the reference source, the higher the CRI. Traditionally, about 80+ CRI is considered “good” for typical commercial applications requiring social interaction, about 90+ for color-critical applications such as higher-end retail. While the standard has endured, it has not been updated in many years, and its limitations are more pronounced with LED technology. In particular, a source may have a high CRI while ineffectively rendering saturated reds commonly found in applications like retail, supermarkets, etc. For this reason, some manufacturers began publishing R9 values to indicate color rendering for saturated reds for sources serving these markets.

The core problem of CRI’s deficiencies remained, however, particularly in light of CRI being used in specifications such ENERGY STAR and the DesignLights Consortium, and in regulations such as California Title 20 and Title 24. In 2015, the Illuminating Engineering Society (IES) published TM-30, a method for evaluating color rendition that introduces two new metrics. First is the Fidelity Index (Rf). Based on 99 color samples instead of 8-14, it was designed as a more accurate alternative to CRI. Second is Gamut Index (Rg), which expresses average color saturation. To determine which colors are saturated or muted, graphics are provided. While more comprehensive and precise than CRI, adoption has been slow.

“Right now, the whole industry is still in the process of educating lighting designers,” said Scheidt. “For the most part, the lighting designers who have heard of TM-30 and understand it really like it and see the benefits of getting more information about the light ahead of time, without having to do trials.”

He added that TM-30 is useful for applications where color is important, such as museums, hospitals, car dealerships, retail, and some offices.

Selling with color
Traditionally, the key to selling with color is to know the customer and the application, understand best practices, and recommend lighting products that will satisfy the need for an appropriate cost. LED is no different, though it can accommodate a broader range of needs, thereby creating new markets. It provides a more powerful tool to explore and understand lighting’s impact on people than traditional sources ever could.

Scheidt said the first step is to do no harm. “It’s fairly simple,” he said. “If the color is bad, then people are not going to like the product and you will have more returns and unhappy customers.”

After that, he pointed out, listen to the customer to find out what they need. “Distributors do not always need to recommend the best color performance or the best color consistency into everything,” he added. “It’s about understanding which customers are going to care about color and which ones aren’t.”

“The only consideration you should need to make is the customer’s preference,” advised Littman.

To produce the right solutions, distributors further need to understand LED technology and the metrics used to evaluate products. “Customers new to LED lighting will look for recommendations, and distributors have the opportunity to help educate the market,” Kites said. “Spectral knowledge and color-tunable systems are new and exciting to the lighting industry, and will bring more challenges and opportunities to the market. The more we know and understand how these systems can positively impact our customers, the bigger the opportunity to bring value to our customers.”

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