A brief article I wrote for tED Magazine. Reprinted with permission.
In Value Metrics for Better Lighting (SPIE Press), Mark S. Rea, PhD, professor and director for the Lighting Research Center at Rensselaer Polytechnic Institute, proposes a new solution to an old problem in the lighting industry.
The industry, he says, has traditionally focused on illuminance (lumens/sq.ft., or footcandles) as the primary metric. Quantity of light once predominated in design, but in recent decades, the notion of quality of lighting—where light is placed and at what intensities, with benefits exceeding simple visual acuity—evolved into best practice.
The problem is quality is hard to define. The long-pursued single metric for it has eluded the industry, primarily because it’s so application specific. There’s no one size fits all when it comes to lighting quality; what’s best for one space may not be best for another.
As a result, Rea asserts, illuminance continues to dominate the value proposition. While some projects go beyond that, all projects include it, making it the lowest common denominator in dialog with clients. Since all lamps and luminaires deliver lumens, the lighting industry’s main product is regarded as a commodity, making competition a fight to deliver light at the lowest initial cost across a majority of the market.
“Lighting should be a value-added profession,” Rea says. “We have to change today’s self-defeating approach to lighting that considers cost—e.g., luminous efficacy and system life—before we even know the client’s needs. We have to address the benefits first, and then the costs.”
He offers two solutions. First, engage the client in a dialog about their needs. Electrical distributors understand this well as part of customer engagement. Second, develop solutions around lighting quality needs based on quantifiable metrics. The result is a sale in which evidence-based lighting quality, not initial cost, dominates the dialog with the client. That is a conversation more likely to create perception of customer value, more actual value, greater competitiveness for the practitioner, and more profitable sales.
“I believe society would pay more for lighting that is based upon metrics shown to improve health, safety and productivity,” Rea says. “That being the case, the benefit to specifiers would be that they would get richer because they can exercise skills the client cares about. Specifically, specifiers need to gain greater skills in engineering the spectrum, amount, distribution, duration and timing of light to meet health, safety and productivity design objectives.”
Rea proposes that the dialog with the customer focus on these potential lighting benefits of productivity, health and safety/security. Once the client prioritizes these needs, solutions can be designed based on solid metrics backed by research.
Because the eye is sensitive to varying levels of illumination and spectrum (wavelengths), Rea proposes several benefit metrics, one in which the lumen is redefined based on what type of vision is predominant in the application, and another in which scene brightness can be determined. For example, sources such as metal halide and LED produce a spectral emission that can make a scene appear brighter than under high-pressure sodium. As brightness has been determined to be linked to perception of safety, metal halide or white LED can achieve the same desired brightness level as high-pressure sodium for fewer lumens, resulting in greater energy efficiency without compromising the design goal.
He also calls on specifiers to focus more on application efficacy than the efficacy (lumens/W) of sources and luminaires. Maximizing application efficacy involves putting light only where (via good optical control) and when (via controls) it is needed. Proper application results in satisfying the same lighting goal but with fewer lumens and less electrical energy.
Lighting for health is an emerging trend, and the Lighting Research Center has conducted a substantial amount of work in this area. Rea proposes metrics addressing intensity, color and duration of exposure to light as a way to deliver effective circadian lighting. He also calls for adoption of new color metrics such as the gamut area index as an adjunct to the traditional CRI metric. This facilitates more precise evaluation of the color rendering properties of light sources, particularly LED, for which the traditional CRI metric by itself often falls short.
“Value metrics become a win for society, a win for clients and a win for skilled lighting specifiers,” Rea concludes. “They will put money in your pocket if you are willing to invest the time to learn. Deliver real value, and it will be rewarded.”
Learn more by reading Rea’s book, Value Metrics for Better Lighting (SPIE Press), and by visiting the Lighting Research Center at lrc.rpi.edu.
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