It’s a Question of Quality: Lighting Upgrades

Image source: Hubbell Lighting
Image source: Hubbell Lighting

Fifty-six percent of European workers said they would like better workplace lighting, according to a survey conducted by Repro-light, a European consortium dedicated to creating the “Luminaire of the Future”—a smart, modular, reconfigurable and customizable luminaire. Many respondents—which included 1,100 workers across German, Spain, Italy and Austria—also believe workplace lighting affects their mood, performance and vigilance. Overall, the survey results showed end-users want personalization, automation and adjustability.

As the LED revolution matures and the technology approaches its practical limit for efficacy, the conversation is shifting from energy-efficiency back toward lighting quality. This conversation goes beyond watts and foot-candles to include visual comfort, space and object perception, flicker, color, aesthetics and more, achieved through quality design and products.

Why is this important? Light is about far more than vision, though visual acuity is important. With good design, lighting can satisfy users, direct attention, create a visual hierarchy in a space, beautify urban nightscapes, make an aesthetic architectural statement and more. The challenge in a lighting upgrade—and even many new construction and renovation projects—is the difficulty in quantifying benefits. A watt saved is easy to communicate and build a return on investment from. However, the value of quality lighting can far exceed any energy savings. Looking at the 3/30/300 (utilities/real estate/employee) rule of thumb cost to operate a square foot of commercial building space, a 50+% reduction in energy costs can be substantial, but even a modest reduction in real estate or improvement in employee output is far higher.

The key elements of quality electric lighting in practice focus on color quality, flicker, visual comfort, light distribution and health and well-being. Color quality is captured by metrics defining color fidelity, chromaticity and saturation. Flicker is an indicator of stability of light output. Visual comfort involves providing pleasing brightness contrast in the field of view. Light distribution defines where light is directed and at what intensity. And lighting for health and well-being involves daylight, views and emerging circadian lighting strategies.

For electrical contractors, understanding quality lighting principles can facilitate installation and commissioning that is supportive of quality lighting design goals. For those that provide design services, enhancing their education about quality lighting can differentiate them from the competition and support a broader range of projects.

Benchmarks

Building and product rating systems previously focused on energy efficiency for energy and sustainability benefits are now increasingly recognizing lighting quality as important. These include the DesignLights Consortium’s (DLC) Qualified Products List, the Leadership in Energy & Environmental Design (LEED) green building rating system, and the WELL Building Standard.

DLC: The DLC’s Qualified Products Lists of LED products and networked lighting control systems offer a resource to the industry for sourcing products and to numerous utilities and energy-efficiency organizations for qualifying products for rebate programs. In 2019, the DLC released its Technical Requirements Version 5.0, which incorporates a new and substantial emphasis on lighting quality for LED products seeking inclusion in the Qualified Products List. It will go into effect in 2020. As of the time of writing, the V5.0 draft requirements necessitated reporting on LED product attributes such as color quality, glare, flicker and light distribution. This will increase the value of the resource and provide specifiers more information to evaluate products beyond basic performance metrics.

LEED: LEED Version 4 includes two options related to interior lighting quality, each valued at one LEED point in the green building rating system. The first option is to give users local control of their lighting in at least 90% of occupied spaces, zoned and with at least one light-level choice between full on and off. LEED emphasizes low-glare luminaires and lamps; color rendering index (CRI) rating of 80+ with few exceptions; indirect lighting (only 25% of installed lighting may have a direct-only distribution); illuminated walls and ceilings; and reflective surfaces, furniture and movable partitions. Other sections of LEED emphasize daylighting and views.

WELL: Created in 2013 by the International WELL Building Institute, the WELL Building Standard provides a building rating system similar to LEED, focused on wellness instead of sustainability. WELL Version 2.0’s features include a spectrum of lighting characteristics that address lighting quality. With a few exceptions, all lighting must have a CRI of 90+; 80+ with an R9 (saturated red) of 50+; or have an IES TM-30 average fidelity rating (Rf) of 78+ and an average saturation rating of 100+. Lighting must operate within a designated frequency to minimize flicker across a wide dimming range or otherwise demonstrate a low flicker risk. With the exception of wall washers and decorative lighting, luminaires must be pure indirect in optical distribution, have an appropriate unified glare rating for the mounting height, be properly shielded, or emit an acceptable brightness level. And WELL 2.0 encourages lighting that is tunable by users and automated to satisfy the visual and circadian needs of the user; supplemental task lighting must be made available that can increase light levels to at least double recommended levels.

While these rating systems don’t tell the whole story of lighting quality—which can best be understood through education by organizations such as the Illuminating Engineering Society (IES)—they provide a roadmap for nonlighting designers and guidance for ECs who design lighting.

Color research

Research has led to a new understanding of color preference based more on color saturation—especially red—as opposed to fidelity. Here, we see a vignette illuminated with an 80 CRI source on the left, and a somewhat lower CRI on the right but with oversaturation, which makes colors, particularly red, more vibrant.
Research has led to a new understanding of color preference based more on color saturation—especially red—as opposed to fidelity. Here, we see a vignette illuminated with an 80 CRI source on the left, and a somewhat lower CRI on the right but with oversaturation, which makes colors, particularly red, more vibrant.

A critical aspect of lighting quality is color, as this characteristic of electric lighting determines how natural faces, objects and spaces appear. Traditionally, color quality focused on fidelity—how well an object appeared under a light source compared to an ideal reference source—as measured on the CRI. Unfortunately, CRI is a flawed metric, and LED lighting accentuates its flaws; what we ended up learning is that color saturation is more important than fidelity in human color preference, according to recent research.

Several studies by the Pacific Northwest National Laboratory and Zhejiang University in Hangzhou, China, confirmed that saturation, notably in the red spectrum, is a key attribute of color preference in both North America and Asia. In the PNNL study, subjects entered a space containing objects such as fruits and clothing along with a mirror to observe skin tones, illuminated under a light source with a correlated color temperature (CCT) of 3,500 Kelvin, considered neutral white. The researchers changed the spectral power distribution of the lighting and asked the subjects to rate each scene. They discovered that color preference—what a typical person would regard as a pleasing light source—correlated with somewhat high fidelity (>74) coupled with oversaturation, particularly the color red.

What does this mean for design? By ensuring sufficient red saturation in addition to fidelity, skin tones in the space appear healthier and more natural, organic materials similarly appear more natural, and colors are overall more vibrant. Light sources with a CRI lower than the accepted 80 can be suitable if combined with color oversaturation. In practice, this would align with the WELL Building Standard requirement described above. To really analyze what a light source can do, get to know the IES TM-30 method for evaluating light source color, which sets aside CRI and focuses on more robust fidelity rating and saturation.

Scientific understanding of the relationship between light and circadian health has grown significantly in the last 10 years, resulting in an emerging trend in lighting design focused on optimizing electric lighting for health and well-being.

Designing circadian-friendly lighting updates traditional design by focusing on vertical light levels, high light levels at certain times of the day, and the use of spectrum to entrain a circadian response. As circadian lighting is fairly new, there is some debate on how it should be promoted and designed. However, the Lighting Research Center at Rensselaer Polytechnic Institute, Troy, N.Y., which has conducted a great deal of research in this area, believes it is actionable today and offers design resources, and the WELL Building Standard encourages it.

WELL 2.0 stipulates that at least 200 equivalent melanopic lux (a circadian light level metric) be emitted from a vertical plane at approximately eye level for occupants at a majority of workstations. This can include daylight and should be present every day at least between 9 a.m. and 1 p.m. Alternatively, the electric lighting should produce a maintained equivalent melanopic lux of at least 150. Separate requirements are outlined for living, break room and learning spaces.

Controls

Best practices—such as individual or group tunability of lighting; automatic tuning for circadian, time of day, daylight integration, or other requirement; and user overrides—require a control system with flexibility and intelligence. This is the front end of what controls can do to support lighting quality. At the back end, things get even more interesting.

By tying all control points in a building or campus to a centralized command point, we can program and fine-tune automation strategies. Further, while pushing out commands to control points, the system operator can pull data out and place it on an organization server or the cloud. This can provide energy measuring, which is useful for energy management and monitoring and maintenance that keeps lighting operating with minimal disruption. It can also be used to optimize space utilization and temperature control. By monitoring light levels, the owner can anticipate the end of LED product life while gaining insights into user light-level preferences.

By adding RFID tags to critical assets, the lighting system could be used to track those assets. Occupancy- and light-sensor data could be fed to third-party software and other building systems for response and analysis. Or additional sensors could be incorporated to measure anything that can and should be measured. All of this information can translate to improved business processes and ideally a higher-quality user environment.

Today’s lighting systems offer enormous potential for energy efficiency and long life but also extended performance. Indirect lighting, ensuring light strikes vertical surfaces in the space, the right color quality, stable light output, flexibility using dimming, color tuning, automation and data all offer ingredients in various recipes for a quality lighting solution.

By becoming educated on what lighting can do and how it should be done, electrical contractors can well position themselves for the growing market for quality lighting.

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