Designing lighting systems and lighting controls
Lighting designers must consider many factors when specifying lighting systems and lighting controls for their designs. In addition to considering the type of lighting fixture, they must also take into account daylighting, lighting controls, codes and standards, and other factors. To ensure these systems work as efficiently and effectively as possible, commissioning new systems (along with ongoing commissioning) is vital for success.
- Understand codes, standards, and guidelines that govern lighting and lighting control design.
- Learn some specific lighting control strategies.
- Learn about the commissioning process.
Quality lighting design has the ability to transform our perception of spaces and create integrated designs that bring architecture to life. Light directly impacts the way we live. Often described as a blend of art and science, lighting design combines artful application with ever-evolving technology. With that said, a truly successful lighting design also requires a complementary control design that produces the right amount of light where and when it is needed.
LED technology offers several key advantages over legacy lighting sources, enabling lighting designers to deliver more to clients. LED systems provide more light while using less energy, introduce fresh, new form factors for lighting systems, and offer increased operational flexibility over their traditional fluorescent, high-intensity discharge (HID), and incandescent predecessors. By properly identifying LED opportunities at the onset of a project and thoughtfully coordinating the systems and equipment needed to achieve the team’s design goals, these advantages can be leveraged to create more sustainable, flexible, and maintainable lighting solutions.
Before diving into product selection and lighting layouts, designers should always begin by assessing the client’s needs. Each project is unique in size, shape, and geographical location, as well as programmatic and stylistic requirements. As a result, a unique set of lighting criteria is needed at the onset of each endeavor. A client’s opinions regarding how they would like their spaces to look, feel, and function, as well as their energy efficiency goals, will have a direct effect on the designer’s approach in establishing the project’s sustainability guidelines. Color temperature, color rendering, and other design criteria related to lighting quality are important to identify early in the project design. The following are examples of design approaches used to select appropriate lighting solutions for a project, as well as options designers and clients alike need to consider throughout the process.
Access to daylight can significantly contribute to occupant satisfaction within a building, and properly controlled daylight in a space also offers an opportunity to reduce the need for electric lighting. Whether required by code or installed as a “best practice,” daylight harvesting uses photosensors to monitor daylight levels in a space and adjusts lighting-fixture outputs to maintain the space’s proper illumination level.
Daylight harvesting is one aspect that can contribute to a project’s sustainability, and there are many factors that may drive a project’s sustainable requirements. The most basic design drivers are the codes and standards established by local governing bodies, and many of these authorities prescribe the use of daylight harvesting and other energy-saving measures wherever practical. These assigned code requirements can greatly affect the lighting design and fixture criteria (therefore, lighting system costs), making early consideration critical. In many cases, standards requiring daylight design integration must be met to obtain approval to construct.
Codes, standards, and guidelines for lighting design
Relevant codes for lighting design include, but are not limited to, the International Building Code (IBC), International Energy Conservation Code (IECC), and ASHRAE 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings. While there are variations within each, these codes establish lighting-power density (LPD) metrics, emergency and egress light levels, and minimum lighting control strategies as major requirements. Each code has multiple editions and is updated regularly (typically a 3-year cycle), as technology changes drive improved efficiency and enhance safety requirements.
The designer’s first task is to determine the version of the code that is applicable to a project based on the year the project’s design starts and the building standards that the local governing body follows. Some areas of the U.S. follow more strict codes, such as California’s Title 24, making it important to stay updated on lighting requirements in various regions.
A big consideration in lighting design is addressing sustainability. Clients and designers choosing to meet the requirements set forth in the U.S. Green Building Council’s LEED guidelines can take advantage of a checklist of sustainable design elements to incorporate. However, unlike building codes, LEED provisions are voluntary. The more sustainable strategies incorporated into the building design, the more credits/points earned, and a higher certification level is received. Lighting quality, control design, LPD, and integration of daylighting strategies can contribute to a project’s LEED scorecard to help achieve Platinum, Gold, Silver, or basic LEED certification. These credits are significantly more achievable with LED technology and modern lighting control systems. Like codes, the LEED guidelines are updated as technology improves, and the current version at the time of writing is LEED v4. Other certification programs, like the WELL Building Standard and Green Globes, are emerging with a slightly broader range of emphasis in terms of the role that lighting can play. For example, requirements to capitalize on the positive people-centric and psychological impacts of light and health in addition to a strong focus on energy efficiency.
Lighting controls are the primary means of providing lighting functionality and saving lighting energy. At the most basic level, the lighting control system design must be in compliance with the most recent edition of ASHRAE 90.1 for the associated jurisdiction. The following strategies (or a combination of strategies) can be incorporated to achieve a compliant design:
- Time/astronomical scheduling: Lighting in a defined area turns on or off, or dims, based on a predetermined, customizable schedule.
- Occupancy/vacancy control: In each zoned area of the building, lighting is turned on, off, or to a predetermined level based on detected occupancy. With “vacancy” control, users must manually turn on lights, but lights are automatically turned off when a space becomes vacated. Often, room conditions may not require electric lighting, as in the case of a daylit office. In this type of situation, vacancy sensors are able to save energy that would have otherwise been automatically consumed if an occupancy sensor forced the lights on. For this reason, vacancy sensors are generally considered more efficient than, therefore preferable to, occupancy sensors, driving the inclusion of prescriptive vacancy sensors in many versions of updated electrical codes.
- Daylight harvesting: Light levels are manually and/or automatically adjusted based on the amount of natural light in a space. Appropriate light levels are provided for functional purposes, and total illumination is maintained throughout the space. Different ways of harvesting daylight include continuous dimming of the lighting systems (the most efficient option), bi- or multilevel zone dimming or switching, or simple on/off controls provided for lighting zones where ample daylight is expected.
- Task tuning: Maximum light levels are set or “tuned” for a particular use or task in a specific room to prevent overlighting and to extend the life of the lighting system.
- Personal control: Individuals can tailor the lighting in their workspace to their personal preferences and needs. This can be achieved by giving each user control over the lighting system in a granular way, or by employing a task/ambient lighting strategy and providing an individual task light at each workstation.
- Control of emergency egress lighting: In the past, lighting on emergency circuits was often left “on” 24/7 as a safety measure, burning through the night long after occupants of a building had left. Advances in control devices now allow emergency lighting circuits to be controlled by time schedules or by automatic sensors. By equipping these devices with a UL 924 emergency transfer device that can override the digital lighting control system if normal power is lost, the system is able to turn on all lights connected to the emergency circuit and maintain egress levels for occupant safety—without wasting energy.
- Building automation system (BAS): The lighting control system can be connected to the BAS to use the occupancy sensors to adjust mechanical setpoints. If multiple lighting control zones are provided in a single mechanical system zone, the lighting control system can accumulate the occupancy zones within the mechanical zone to help refine the efficiency of the HVAC system.
- Specific area examples:
- Interior private offices or rooms: Occupants turn lights on and off by pressing a low-voltage wall switch. A ceiling-mounted vacancy sensor turns off the room lighting if occupants forget to turn it off when they leave.
- Perimeter offices or rooms with adequate daylight: Occupants turn lights on and off by pressing a low-voltage wall switch. This switch turns on the lights to a level allowed by a photosensor that monitors the amount of daylight intensity at the associated workplane. A ceiling-mounted vacancy sensor turns off the room lighting if occupants forget to turn it off when they leave.
- Corridors and lobby: These are usually the only building areas with two modes of operation: “during business hours” and “after business hours.” In the corridors, an array of occupancy sensors turn lighting on and off according to occupancy and the current response mode, dictated by the lighting control system’s time clock. Perimeter areas are also equipped with photo sensors to adjust the amount of electric light based on the amount of daylight in the space. Lights in these areas are adjusted to lower level output when a load-shed signal is sent while always maintaining code-required illuminance minimums.
- During business hours: Upon detecting occupancy in a corridor, the lighting control system turns on lights and keeps them on until the system enters “after business hours” mode, after which point it only turns on lights when the building has occupancy, preventing the corridors from lighting up on holidays, snow days, and other low-occupancy days. Lighting remains on in the corridor throughout the business day once triggered, preventing short on-off cycling of corridor lighting as occupants move from space to space. At the end of “during business hours,” the system transfers to the “after business hours” lighting control mode.
- After business hours: Occupancy sensors control corridor lighting via auto-on and auto-off functions. After 15 minutes of non-detection, lighting automatically turns off (which can be turned back on with movement or using a manual override if needed). Minimum cycling of lighting is expected during these low-occupancy hours.
- During load-shedding intervals: Certain building areas or luminaire types may be connected to central utility systems to receive a load-reduction signal when the power supply is low, to avoid brownouts. Nonessential lighting loads in corridors and lobbies (accent lighting, decorative lighting, etc.) can be good candidates for load-shedding applications.
- Restrooms and stair towers: Lighting in these rooms is determined 24/7 by occupancy sensors. After 15 minutes of non-detection, the lighting automatically decreases to a lower preset level or turns off (which can be turned back on with movement or by using a manual override if needed).
- Utility and storage rooms: Occupants turn lights on and off by pressing a low-voltage switch on the wall. A 2-hour timeout sequence starts when the switch is activated. A blink warn occurs when 5 minutes remain in the 2-hour countdown. If the user wants to remain in the room, the switch can be activated again, and another 2-hour timeout sequence commences. Luminaires in these areas are adjusted to a lower level output when a load-shed signal is sent. It is worth noting that NFPA 70: National Electrical Code (NEC), Article 100.26 (D), requires a manual switch/override for electrical rooms.
- Conference rooms: Occupants turn the lights on and off by either pressing a low-voltage wall switch or using a preset scene-dimming control station. Ceiling-mounted occupancy sensors operating in vacancy mode turn off the lighting if occupants leave but forget to turn off the lights. Maximum light levels are set for this space for certain tasks.
In addition to code-compliance considerations, lighting controls are usually required to achieve a project’s aesthetic goals or owner’s functionality requirements. Today’s LED lighting systems offer many choices to designers in regard to color and dynamics, enabled by coordinating lighting control technologies on the back end. Digital multiplexing (DMX), Digital addressable lighting interface (DALI), Power over Ethernet, and even wireless systems can be used to control LED color and intensity in new ways, and they are becoming more commonplace with the prevalence of LED systems that offer designers additional features to satisfy a client’s needs.
Commissioning lighting controls
Both ASHRAE 90.1 and IECC require commissioning of all control hardware and software to ensure that these elements perform as intended. The commissioning agent verifies that the controls’ locations, adjustment, aiming, calibration, and programming all align with construction documents, field conditions, and manufacturer instructions.
The commissioning of lighting controls generally needs to be done before occupancy and outside of a space’s normal work hours, often requiring nighttime calibration for daylight-harvesting systems. The commissioning agent performs a number of procedures to test automatic sensors, photosensor and daylighting controls, time switches, and programmable schedule controls. Sensors are inspected to ensure they are correctly placed and their sensitivity and time-out adjustments deliver performance. Programmable schedule controls and time switches are tested to make sure they are set to turn off the lights as intended. Photosensor controls are inspected to ensure their placement and sensitivity adjustments achieve the desired reduction in electric lighting based on available daylight. The commissioning of a daylight-harvesting system often is required to occur at night so the true output of the electric system can be factored into the photosensor programming without any daylight contributions.
The lighting control system itself is also commissioned. The manufacturer of the system builds in testing procedures for individual components, such as onboard fixture controllers, to allow them to be checked when they are being installed. The system also takes stock of all components that are connected to it, allowing the commissioning agent to detect any unconnected or “orphaned” components. The commissioning agent also checks zoning, or the grouping of lights, and the system’s programming including control profiles, schedules, and load-shedding sequences.
Engineers and designers can aid the commissioning process by requesting the following items in the design specifications as part of the system submittal: programming-intent narrative, a detailed bill of material, contractor checklist, and start-up request form.
A good lighting design incorporates easy to use lighting control systems. This balance makes building spaces functional and comfortable for all occupants.