Heart of the issue


At the core of one of light’s biggest effects on human health is its nonvisual effect on the body’s circadian system. The circadian system produces and regulates bodily functions based on 24-hour cycles, called circadian rhythms. Examples of circadian rhythms include sleep-wake cycles, core body temperature changes, and the release timing of hormones, such as melatonin. Disruption to circadian rhythms can lead to poor nighttime sleep and increased daytime napping as well as a 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 local position on Earth. The human eye contains various cells receptive to light. Together with rods and cones, recently discovered intrinsically photoreceptive retinal ganglion cells, which are connected directly to the brain’s master clock, convert light into neural signals for regulating the timing of the circadian system.

For millions of years, sunrise and sunset primarily regulated the human circadian system. Today, we use electrical light sources, which also stimulate our circadian system. Designed primarily for vision, electrical lighting can provide too much or too little illumination to properly drive the circadian system. This uncertainty in light exposure can cause circadian disruption.

As our understanding of the science increases, it also creates opportunities to enjoy the visual and aesthetic benefits of electrical lighting while designing lighting systems that are conducive to proper circadian regulation.

What we can do


Mariana G. Figueiro, professor and light and health program director at the Lighting Research Center, Rensselaer Polytechnic Institute, Troy, N.Y., has been studying the relationship between light and health for years. She said four primary characteristics influence light’s effect on the circadian system.

Intensity is the quantity of light the eye’s photoreceptors receive during the day. In application, we are talking about light levels falling on the eye.

Figueiro said this factor may be predominant in circadian response. She said that vertical light levels are important here, rather than the horizontal (workplane) light levels that are typically the focus of lighting design for visual performance. This would entail ensuring vertical surfaces, such as cubicle walls, are properly lighted. It is a shift in traditional practice.

Optimal light levels can be calculated, but generally, a light level of about 30–40 vertical foot-candles (which translates to roughly 80–120 horizontal foot-candles) is desirable in the morning. Providing these light levels is currently at odds with commercial building energy codes. In fact, light levels suitable for energy codes based on visibility are sometimes too low to activate the circadian system, which is a big problem, Figueiro said. Ideally, light level will be variable throughout the day through supplemental task lighting and controls.

In the evening, starting about two hours before bedtime, a much lower vertical light level of 1–2 foot-candles is desirable.

Spectrum is the wavelength (typically associated with related color perception) of the light. While visual acuity is most responsive to medium-wavelength light [around 555 nanometers (nm), or “green”], circadian regulation is most responsive to short-wavelength light (460 nm, or “blue”). As a result, there is greater interest in lamps with a very cool correlated color temperature (5,000K-plus) and color-tuning light-emitting diode (LED) luminaires.

However, while research suggests spectrum can increase circadian response by a factor of two, Figueiro said increasing light levels is a more effective way to entrain the circadian system during the day. Both spectrum and quantity of light must be considered.

Further, while short-wavelength light can trigger a strong circadian response, red light can increase daytime and nighttime alertness and affect production of hormones, such as cortisol. So, red wavelengths, in addition to blue, are important.

Timing is when the eye’s photoreceptors receive light. People who work during the day require different light-exposure timing than people who work at night. The same intensity and spectrum delivered in the morning will have a different effect on sleep time than if received in the evening. In short, morning light aids going to bed earlier, while evening light will delay the timing of sleep.

Duration is the amount of exposure time. Intensity is important, but the circadian system really responds to the cumulative quantity of light the eye’s photoreceptors receive during the day. In short, the circadian system doesn’t turn on a dime. It essentially sums up morning and evening light and uses the net result to either advance or delay the body’s internal clock.

“We need to know these characteristics before we can determine what constitutes healthy lighting for each of us,” Figueiro said.

Approaches in lighting that include wireless and mobile control are poised to meet many of the 21st-century client’s needs. There were plenty of examples at Lightfair International 2015 this past May in New York.

Wireless and networked


“I think smart, energy-saving and wireless light control systems will open tremendous new market opportunities for electrical contractors,” said Nick Shkordoff, group vice president and general manager—Ideal Electrical, Ideal Industries Inc., Sycamore, Ill. “We are seeing a switchover to wireless, notably in renovation projects. The control systems are increasingly easy to install, commission and operate to help drive real energy savings. Their simplicity removes some IT wariness for ECs, allowing them to easily install and program these systems and teach them to operations managers.”

Shkordoff expects wireless-supported energy management systems to generate “tremendous global demand,” driving down installation and operating costs, notably across large-scale projects (250,000 to 1 million-plus square feet).

“Changing building codes in California and New York are mandating large-scale energy management systems,” he said. “New ASHRAE 90.1 2013 code has been adopted by more than 11 states, and we believe all remaining states will need to adopt it within two years. By 2017, no U.S. building permits will be rewarded without 100 percent compliance with these ASHRAE requirements.”

Ideal’s Audacy wireless system has been delivering energy savings from 35 to 50 percent, Shkordoff said. It uses a 950-megahertz (Mhz) frequency.

“The spectrum allows us to communicate point to point at 300 feet, and then repeaters from greater distances,” said Nolan Bello, Ideal business unit manager.

Other companies have targeted the same frequency range or lower so lighting controls don’t interfere with other wireless devices, while still enabling frequency communication through walls, floors and ceilings. It is a tremendous advantage for large-scale and multifloor installations, but it benefits smaller installations as well.

Some examples: Lutron’s Clear Connect frequency band for commercial and residential is set at 434 Mhz. Enlighted Inc., a sensor and analytics provider based in Sunnyvale, Calif., likes the higher gigahertz Wi-Fi spectrum for its networked energy system, enabling heavy data communication with a system designed at low wattage to reduce energy use.

For Ideal and others, the fact that their controls can be retrofitted to existing fixtures is key to their market penetration. For example, Ideal’s Audacy Smart Connector is embedded into the fixture to adjust to ambient lighting, motion and occupancy.

The question sometimes raised is whether wireless poses a threat to the EC. Brian Donlon, sales vice president, North America for Lutron, sees it as an opportunity.

“There will always be a load source requiring the EC,” he said. “The wireless components are merely building devices to control what’s electrified: a (0–10V) control signal to run the fixtures. In some cases, wireless control may have a slightly higher price than wired controls, but the reduced labor and wiring costs enable contractors to meet budget constraints, energy goals, and performance requirements and, in effect, capture more jobs that have previously been financially out of reach.”

Donlon finds wireless is also helping contractors improve design flexibility for their clients.

“Commercially, that [installation] might be personal control over a workstation, scene control at a podium, in an auditorium or classroom, or daylight control in open office areas,” he said. “Residentially, the contractor can easily provide control from a bedside or end table, add an additional control location, or even facilitate control from a smart device. As wireless capability becomes even more robust, clients will be able to easily link wireless devices throughout their home or building.”

Tool manufacturers and lighting companies offer an impressive selection of work site lighting options, from flashlights to compact, lithium-ion powered work lights to light towers and strings of LED fixtures to illuminate large areas.

For this report, toolmakers Bosch, Makita and Milwaukee Tool, as well as lighting specialists Larson Electronics and Molex, discuss LED work lights and the benefits of using this technology.

Higher cost once was a barrier to increased LED lamp usage, but prices have lowered significantly. In addition, LED proponents argue that savings from longer life and reduced power consumption offset the cost difference.

About the technology

The biggest advantage LEDs have over traditional work lights is durability, said Jeremy Blankenship, lighting designer for Larson Electronics, maker of LED work lights that range from flashlights to LED light towers.

“With gas-burning lamps, there always is a glass lamp that can be broken due to rough handling, dropping the work light, impacts or vibration,” Blankenship said. “With filament-style traditional lamps, the filament itself is highly susceptible to impacts and vibrations that may sever the filament, which can result in premature lamp failure while the glass lamp remains intact. With LED solid-state technology, these recurring issues are resolved. LED work lamps make for a more reliable and stable work light, reducing maintenance and downtime within the work field due to lamp burnouts.”

LED technology is highly efficient and provides the same output at a lower wattage than traditional lighting fixtures, while providing an increased lamp life.

“Incandescent and halogen lamps are very inefficient and have a very short lamp life,” Blankenship said. “Fluorescent and compact fluorescent lamps are an improvement over incandescent and halogen lamps but still fall short when compared to LED lighting. With LED work lights, an operator is able to obtain the same light output or increased light output over the previous traditional lighting. These LED light sources decrease electrical consumption, which results in low electrical bills in line voltage work lamps and increased battery run time in rechargeable work lights. And, they obtain a light source that lasts 50,000-plus hours, which is double the lifespan of fluorescent, metal halide and high-pressure sodium lamps.”

Safety is another benefit.

“All light sources generate heat,” Blankenship said. “Traditional work lamps, such as the common 500W quartz work lights or 100W incandescent drop lights, reach high surface temperatures, which introduce a burn risk to anyone that allows prolonged skin contact with the light source, as well as a fire hazard if a flammable material is accidentally set too close to the light source for an extended period of time. While LED fixtures do produce heat, they are designed with heat sinks to properly disperse the heat.”

Beyond safety, high upfront costs have been a drawback for LEDs. However, LED prices have dropped.

“Within the last 5 to 10 years, LED technology has made significant advancements in efficiency for light output as well as price point,” Blankenship said. “This has allowed manufacturers of LED work lights to pass these cost savings to customers. With higher efficacy in light output for LED fixtures and higher efficiency in cost of manufacturing, LED work lights are becoming readily affordable to be used in the work place and [to] replace traditional work lamps.

“For now, LED lamps will still be more expensive than bottom-dollar incandescent lamps, but there are countless cost savings in the long run with the LED fixture, resulting in a return on investment and making the LED product the cheaper buy over a period of time,” he said.

Molex manufactures LED fixtures to illuminate large industrial environments for construction and maintenance.

“This is an exciting time for LED fixtures in industrial environments,” said Tom McCollum, Molex global product manager. “We still are in the early stages of adoption with new technology coming out every day, making LEDs more affordable, more efficient and with higher and higher levels of performance. Historically, we have had lighting designs that remain unchanged for years or decades, but those days are over.”
For industrial work environments, the primary benefit is that LED light sources are inherently more durable than traditional light sources, McCollum said.

“That increased durability and very long life for LED light sources means that the need to maintain LED fixtures is greatly diminished,” he said. “Instead of breaking an incandescent filament during rough handling or having to replace a traditional light source after just a few weeks or months of use, LED fixtures can withstand the rough handling and can last for years. Additionally, for fixtures of similar light output, LED versions run much more efficiently than fixtures with more traditional light sources, such as incandescent or various HID lamps. One LED series of products is rated Class I, Division 2, for use in hazardous environments.”

There are a few drawbacks, but most are easily rectified.

“LEDs tend to act as a point source but are usually focused in one direction [e.g., in an area that is less than 180 degrees] and thus may need to be managed to ensure emitted light is directed in the desired locations,” McCollum said. “Getting the fixture to produce bidirectional or omnidirectional or even tightly focused beams of light can be achieved by utilizing multiple LEDs within the fixture that are oriented in different directions or by using lenses and diffusers to direct the light in the desired directions.

“LED fixtures typically cost more up front yet save money over the years by minimizing maintenance and operating costs simply due to the reduced power consumption of the LED fixture,”.