Designing lighting system controls with the user in mind
With a heightened awareness of the physiological effects of light, tunable lighting systems are being developed with the intent to foster healthy circadian cycles.
- Learn about the recent ANSI/IES LP-16-22: Documenting Control Intent Narratives and Sequences of Operations.
- Understand control system considerations for tunable lighting environments.
- Understand different control strategies for tunable lighting environments.
Lighting system insights
- Lighting system controls can enhance lighting systems in commercial buildings and several tools are available to help engineers and lighting designers.
- ANSI/IES LP-16-22 Standard Lighting Practice can help guide a designer when creating a lighting control system.
Sophisticated lighting systems have become the new standard, with increasing options for light fixtures, light sources and lighting controls. Though the intricate nature of modern lighting systems often requires additional, specialized expertise, numerous benefits can be achieved through a careful approach to lighting planning, programming and design.
Advanced lighting controls can ensure lighting turns on/off automatically during scheduled times, determine when spaces are unoccupied or occupied and assess available daylighting. To maximize energy savings, ANSI/IES LP-16-22 Standard Lighting Practice: Documenting Control Intent Narratives and Sequences of Operation, published in July 2022, serves as an excellent tool for the development of any lighting control system.
The standard clearly outlines the purpose that both a control intent narrative and sequence of operations, play in the specification and programming of a control system. The CIN is typically documented by the electrical engineer and is developed in collaboration with the architect, interior designer and/or lighting designer in response to owner requirements and proposed designer control intent. It is documented early as part of the project basis of design that describes the overall intentions for the specified system.
Because the intent is to give the owner and end user a high-level overview of various system attributes for review and comment, the CIN cannot be relied on for project details. It should include elements such as:
- System scale: whole building or single room.
- General information about user interfaces and sensors, wired or wireless.
- Key infrastructure or network requirements.
- Specific requirements that may lead the project down a sole-sourcing path.
Continual refinement of the CIN is performed simultaneously with the development of the SOO. The SOO provides contractually enforceable language to inform the installer how to program the system to meet design intent, focusing on the programming and functional requirements of the equipment. The language of the SOO becomes prescriptive as specific requirements and expectations are outlined.
For instance, where the CIN may generally indicate that keypads or touchscreens will be required, the SOO includes the specific engraving or graphic details of each station. Or, regarding sensors for occupancy or vacancy response, the CIN may note that sensors provide on/off or partial dimming while the SOO includes specific setpoints, timing and methods.
As clearly noted in the standard, walking the design through a series of steps will ensure that each element is clearly developed. For the CIN, the steps include answering the following questions:
- What does the owner want and consider important for end-user needs?
- What are the spaces involved?
- How do various devices interface to provide control?
- What are code-required and certification-required functions?
- How does the system function? Is there specialized control or automatic programming?
- Is the lighting in the environment expected to change?
- What are the specific conditions in which the system will react?
For the SOO, a similar list of steps is included, but with more detailed specification of how to achieve the CIN. In general, the SOO should:
- Define the devices and equipment required to enable the system to meet design intent and code-required functions.
- List the spaces integrated with the control system, including exterior environments.
- Define actions and functional responses in typical use cases including the start and end points of each operation. This includes system on/off programming for large areas as well as specific device responses.
Lighting system controls
The abbreviated narrative and table below exemplify this progression from general control information in narrative form to a table format providing concise direction and documentation. Note that every project has its own set of requirements. The information noted below is for example only.
General overall system narrative indicates that the lighting system shall:
- Facilitate configuration, monitoring and reporting via a computer software interface.
- Be networked together, enabling communication between devices.
- Be capable of centralized and distributed intelligence.
Use 0- to 10-volt control protocol.
- Be a fully wired system (no wireless control is allowed).
Include occupancy, vacancy and photosensors as required that carry 0- to 10-volt control signals for communication.
- Be connected to the building automation system; BAS shall provide time clock function to the lighting control system and all configuration and monitoring shall be accomplished through the lighting control system software.
- Control exterior building illumination, main entry lobby, public corridors and conference room.
General control intent for a couple of the areas noted may include the content below.
Main entry lobby shall have:
- Timeclock scheduling for programmed daytime/nighttime illumination and automatic off.
- Low-voltage manual interface for after-hours override.
- Photocell interface for daylight harvesting where daylight is present.
- Normal power and emergency power lighting controlled together.
- Emergency lighting programmed to remain on at the level required for eqress illumination at any point when normal lighting is turned off.
Conference room shall have:
- Four unique preset scenes.
- Vacancy sensors for manual on/auto off control with low-voltage manual interface.
- Photocell interface for daylight harvesting where daylight is present.
Identifying lighting spaces
The design guideline also includes verbiage for foundational strategies for typical space types such as private offices, open office, corridor, classrooms, conference rooms, multipurpose rooms, religious worship spaces, etc. While many examples have been provided, strategies pertaining specifically to health care design and circadian lighting have been understandably omitted due to their complexity and the many variables and metrics that must be considered.
The LED revolution has paved the way for products that include:
- Multiple white color temperatures, tunable white and targeted spectra.
- Complex lighting systems used to set a mood through the use of color.
- Conveyance of the passage of time through gradual color and/or intensity changes.
- Circadian stimulation through a spectrally tuned system.
For each, it is important to understand that correlated color temperature, expressed in Kelvins, is a description of light source color appearance. For example, 2,700 K light is generally described as “warm” (yellowish), 3,500 K is a more neutral white and 5,000 K or greater is “cool” (bluish).
While this single number is an industry standard to convey the appearance of a “white” light, it does not provide important information on the spectral content of that light, referred to as spectral power distribution. A light’s SPD indicates the amount of power it contains at each wavelength along the electromagnetic spectrum.
For luminaires that offer color or spectrum adjustment, there are three primary strategies by which the luminous flux and/or spectral power distribution of a lamp or luminaire is adjusted: warm dim, white tuning and color tuning. The appropriate strategy is selected based on spatial needs and is implemented using luminaires that permit the necessary control of spectral power distribution. Manufacturers use different names for these, but most strategies of color/spectrum adjustment fit within one of these three categories.
Warm dim, also known as “dim to warm,” is the simplest of the three. As the control level is reduced from the maximum level, the color temperature shifts to a lower value (appears warmer) and intensity are reduced. This approach enables the user to mimic the dimming behavior of incandescent lamps without requiring the complexity of separately adjustable CCT and intensity.
White tuning, often referred to as tunable white, is the mixing of two or more independently controlled white LED boards — warm white and cool white, typically with a color temperature difference of 1,000 K or more. Resultant color temperature variation can be achieved by changing the relative intensity of the boards.
Color tuning (or spectral tuning) uses a combination of multiple LEDs typically with narrower wavelength ranges to achieve more saturated colors and/or tailored spectral distributions. Color tuning lights may be used to emulate the appearance of daylight throughout the day or to provide efficient circadian stimulation when daylight is not available.
A related concept is circadian lighting. Circadian lighting is designed to have a biological impact on the human circadian system — sending signals to the master clock in the brain, regulating various biological functions based on daytime and nighttime hours. If one is outside for significant portions of the day, this calibration in the body happens automatically in response to natural daylight.
However, based on a study by UC Berkeley and the Environmental Protection Agency in 2001, nearly 90% of our day is spent inside. As a result, we are often missing the daytime circadian signals that our bodies need. Research has shown a sustained exposure to low-quality daytime stimulus can have long-term adverse effects. Circadian lighting systems are developed with the intent to provide benefits that could help reduce chronic health conditions related to our indoor lifestyle by improving mood, sleep and overall sense of well-being.
Although there are a variety of metrics used to determine the circadian stimulus of a lighting system, these are not fully agreed upon by the lighting community. There is, however, a consensus that spectrum, timing and duration are a few of the critical considerations leading to successful system design.
While the spectrum is an element inherent to the luminaires being used, the control system must be able to operate the luminaire per the manufacturer’s control protocol. For some luminaires, this may require a proprietary system. If a space has luminaires with different sources and in particular, sources with different color qualities, a standard protocol is beneficial and allows for a wider variety of potential control systems.
An effective circadian system is reliant on a repeated daily lighting cycle with consistent timing and duration, thus, the lighting on/off schedule and transitions throughout the day must be considered. If the system is deployed in a standard office environment, the schedule may be based on typical office hours, but for a health care environment that operates 24/7, the system should consider staff shift schedules, visiting hours and quiet hours.
While some projects may be focused on creating a circadian-effective design, others may use a white tuning or color tuning system for a psychological response. In lieu of an automated system with a rigorous schedule, these systems may instead be focused on a change in the lighting to create a mood or respond to user preferences.
Although schedule may be important in mood creation in a restaurant environment, defined operation and intuitive user interfaces enabling each person to select their personalized and preferred color becomes far more important. When working through project design parameters with the design team, each of these elements factors into the final control narrative. Given the consideration required and the potential system complexity to address each, it is critical that the owner supports the design approach during the early programming and schematic phases of the project.
This support may be derived based on specific project programming (i.e., windowless spaces), their inherent support of wellness initiatives for employees in the work environment (pursuing WELL certification) or because of education by the design team. Initial discussion and education early, will provide the understanding required when the initial BOD is developed, reviewed and inevitably priced.
Lighting system examples
Through the following project examples — with a focus on a higher education and a health care project expertise — ranging from a simple manually selectable tunable white system to a circadian system in a hospital environment, the insight required for these complex systems is explored.
The Ryan Walter Athletic Center in Evanston, Illinois, is a versatile practice, competition and recreation facility for Northwestern University. The center provides a central training location for athletes and coaches, complete with meeting rooms and a sports performance center. The performance center features an office for the team psychologist specializing in individual counseling and mental health services for student athletes.
When a circadian lighting system was requested, a variety of questions and concerns arose. Based on further dialogue with the NU staff, the request was to provide the team psychologist the ability to change the color and intensity of his office lighting, creating an environment to help calm or energize patients based on individual need. A standard tunable white linear suspended pendant was selected.
When considering the CIN, the CIN for this application would simply be “the linear suspended luminaire will allow for manual selection of color temperature and intensity separately.” However, for further explanation in the SOO, the description should include “the ceiling mount vacancy sensor shall require manual on operation.”
In addition, “separate wall-mount dimmers, controlling color temperature and intensity shall allow users to select levels of each.” Note that while tunable white applications may often be associated with a costly system, understanding the exact owner request allows the design team to provide the flexibility required with minimal added cost.
In contrast to the simple system above, at the Kentucky Children’s Hospital in Lexington, Kentucky, a circadian lighting system was requested for the neonatal intensive care unit renovation and expansion. All patient rooms had to be designed without windows due to the existing floor plan and configurations. The planned lighting configuration included single rooms featuring day and night cycles and the elimination of shared, dark rooms.
For this project, the design parameters and the CIN included a 7 a.m. to 7 p.m. “daytime” schedule that appeared simple and straightforward. The planned system included white tuning capability between 3,000 K and 5,000 K. The lighting system’s color and intensity parameters were programmed for scheduled transitions at specific intervals in morning, evening and nighttime hours.
When issued for construction, the project control specifications included a CIN that indicated two different color temperatures of static white with programmed daytime/nighttime fades at sunrise and sunset. Manual override was to be provided by select button stations within each patient room. Some manual overrides were to allow raise/lower of light intensity without affecting color selection. Others were to provide full-on illumination for emergency procedures, while other override conditions required a minimal amount of light for nighttime rounds.
Because the lighting was programmed for different color temperatures at different the times of day, the override programming became quite complex. To provide a SOO that fully detailed the programming required and fully considered the users and their interactions with the space, the initial half page description exploded to five pages and multiple iterations.
As the SOO was developed, a series of events was created to describe preset scenes through the day. Each scene required setting not only luminous intensity, but also color temperature (using cool white and warm white LED boards) based on the time of day and careful consideration was required to ensure that button activation at any time would respond appropriately.
Through tedious collaboration with the lighting control manufacturer and their on-site system programmer, the details were ironed out and an initial round of programming was completed. At this point, the design team visited the site and the initial design intent was given a visual review. While the initial controls description indicated a high color temperature from 7 a.m. to 7 p.m., it was quickly noted that waking up to a very cool color temperature in the early morning hours would not be welcomed by family members who had stayed overnight with their infant.
As a result, an early morning scene beginning with a warmer color temperature was created. Each scene required the definition of both color temperature and intensity, with timing noted to ensure that the transition was relatively smooth. Once the scene definitions were complete, the local overrides were addressed. Although the system was running throughout the day, overrides of any of the preset scenes were required for procedural reasons.
The “exam” control, providing the highest level of lighting possible by turning all lights on, was located both at the room entry door and at the headwall. Two adjacent button stations at the room entry controlled only the downlights, giving nurses access to lower illumination for night checks.
The final written SOO for each button of the “exam” scene indicated:
- If program button setting is active, the automated sequence will change lighting color and intensity automatically through the day and night.
- If the off button setting is active, the automated sequence will be disabled.
- If the on button setting is active, the automated sequence will be disabled and all lights will remain on at 5,000 K color at 100% intensity.
Writing a SOO for the ceiling and soffit downlight zones was quite simple with only on, off and raise/lower buttons required at each. However, because the system was programmed for different colors throughout the day, definition was required to ensure that whenever an override occurred, the lighting would come on to the appropriate color temperature. When overriding patient downlights to on, the on button must be pressed before the raise/lower buttons, otherwise the color temperature of the lighting would be out of sync with the schedule.
Note that understanding the detailed way in which a control system will be able to address manual override while color and/or spectrum is changing in the background should be part of the initial system selection and development of the CIN.
While significant thought went into the programming of each button for this application, it became clear that there were still some risks with the final approach. For instance, if when leaving the room after a nighttime check, the staff pushed the off button, the lighting would remain off until the “program” button was reactivated.
Alternatively, if the on button was pushed, the lighting may remain on at full for far longer than intended. Given the intent for the system to provide cycled lighting that would promote circadian support, incorrect use of the manual overrides allowing the lighting remain in either given state (on or off) would jeopardize the design intent of the cycled system.
Fortunately, the design team was able to stay connected to the project and, by working with Pacific Northwest National Laboratory, has been tracking the frequency with which those overrides occur. The technical paper “Lighting System Control Data to Improve Design and Operation: Tunable Lighting System Data from NICU Patient Rooms“ in the May 2022 edition of IES research journal LEUKOS provides insight into the installed operation of the system.
The two examples provided here illustrate a stark contrast in the complexity that may be required for the control of a color/spectral tuning project. It is understandable that the new lighting practice standard did not include a full exploration of these parameters, but the thought and time required to develop a fully designed SOO for a complex health care environment should not be underestimated.
While not always straightforward to design, new lighting and control technologies open up a world of possibilities to deliver light to occupants in a more tailored and refined way than ever before. When all of the relevant parameters are carefully considered and documented, tunable lighting systems have the potential to make a real, positive, impact on people’s lives.