Lighting controls: Best practices begins with a strategy
ASHRAE Standard 90.1 requires lighting professionals to include power allowances, daylighting controls, functional testing, and submittals in their lighting designs. This discussion includes an overview of lighting control options along with best practices for lighting designers and electrical engineers in working with their clients.
- Learn how to create a lighting control strategy through client inquiry.
- Identify best practices for lighting designers to work with clients in making smart lighting decisions.
- Identify how human factors impact lighting outcomes and energy strategies.
Lighting controls, coupled with lamp technology, have evolved toward more automated design and away from reliance on human intervention with the goal of saving energy. This automated approach contributes to a net zero or near net zero building design by adjusting the artificial lighting output to ensure the room is not overlit.
A critical part of successful energy-saving lighting control design is occupant education—making sure the occupants understand how their lights are controlled and how they can best use the designed system. This also may include recommendations for users to schedule regular adjustments to the light output over the life of the lamp, allowing for less use when new lights are more intense, and increasing light output as lamps lose intensity toward the end of life, thus saving energy and money.
Best lighting control practices begin with determining a lighting control strategy. Almost all states have adopted an energy code, with the primary code used being equivalent to ASHRAE Standard 90.1-2007 or International Energy Conservation Code (IECC) 2009. Many more states are moving toward adoption of ASHRAE Standard 90.1-2013 or IECC 2012.
Although there are specific codes and standards, many options fit within those guidelines. The following five questions can assist in the decision-making process for clients and engineers:
- How will the facility be used? The type of facility and how it will be used will determine a general direction for the lighting controls. For example, a 24/7 mission critical facility such as a hospital, correctional facility, or data center will have different functional requirements and goals than a general office building or an educational facility. So, levels of importance for lighting controls will vary between the type of facility as well as the individual spaces within each facility. For example, a large cafeteria space requires different controls than a corridor or classroom.
- What are the client’s energy goals? The facility owner’s energy goals and municipal code directives will mandate specific lighting control requirements that, in turn, will inform potential decisions with respect to a lighting control strategy, whether it is a new facility or an existing facility. Such considerations may include meeting a net zero challenge, a Watt/sq ft requirement, facility owner standard or preference, energy rebates requirements, and cost of installation and maintenance.
- What type of user will operate the facility? The level of complexity of a system, as well as the sophistication level of the users, can determine if a central lighting control system is affordable and preferred, or if individual spaces will be controlled independent of one another. If an end user does not have a tech-savvy facility management team, it might be in its best interests to keep the system as simple as possible with individual room controls, such as stand-alone occupancy sensors and manual switches for daylight controls.
- What are the safety and emergency requirements? Lighting controls that consider maintaining safety during power outages while saving energy is another consideration. In these instances, an emergency relay device is required to turn on controlled lighting during an outage to comply with codes and standards. This inherently incorporates emergency egress lighting into the lighting control scheme. With corridor lighting controlled by a relay panel, low-voltage switches can be locked out when the building is occupied, which prevents required egress lighting from being shut off inadvertently. If the facility is used after-hours, the switch could function normally, allowing corridor lighting to be manually turned on and off as needed.
- Are safety and budget issues in balance? Sometimes, the drive to save energy eliminates night-lighting strategies to illuminate the interior of buildings for security purposes. Night-lighting is often used to deter vandalism or breaking into and entering a building. Occupancy sensors can aid in this aspect by turning lights on when someone is moving through the building, inherently incorporating night-lighting into the lighting control scheme.
Minimum controls for ASHRAE 90.1-2010
Minimum compliant lighting controls consist of a combination of manual, time clock, or occupancy sensing devices:
- All interior spaces require manual control to allow occupants the ability to turn the lights off as conditions allow. Most spaces also must provide stepped control in the space to allow for multiple lighting levels. An individual control device can control a maximum of 2,500 sq ft, or if the space is larger than 10,000 sq ft, the area it can control increases to 10,000 sq ft.
- Most interior spaces in buildings greater than 5000 sq ft also require a means for turning the lights off automatically when the space is unoccupied. Automatic off controls can be accomplished in several ways. For example, a time clock turns lights off at the end of the normal day. Occupancy sensors turn lights off once the space is unoccupied, with a maximum delay of 30 minutes.
- Occupancy sensors should be used in a manual on/automatic off configuration, when possible, which is now an ASHRAE Standard 90.1-2010 code minimum requirement. The more people are used to turning lights on with a switch, the more likely they are to turn lights off when they leave a room. Too often, when an occupancy sensor is used as a means to automatically turn lights on, occupants do not consider turning lights off when they leave the room because the occupancy sensor will accomplish that task for them, thus leaving the lights on in an empty room for the time setting of the occupancy sensor.
- Either manual or automatic daylight harvesting controls are required (according to ASHRAE 90.1-2007 and IECC 2009), depending on the size and arrangement of the individual daylighting zone (sidelight or skylight).
- Exterior lighting controls must prevent lighting from being on during daylight hours. Exterior façade and landscape fixtures must be shut off at a certain time during the night, and all other non-emergency or non-security exterior lighting must be reduced by a minimum of 30% between midnight and 6 a.m. or outside of business operating hours.
Several strategies, with little additional cost, can be explored to increase savings over minimum compliant controls:
- Consider multi-level lighting, with switches in strategic locations. For example, in a classroom, a single switch could be located near the entry door, which would turn on the lights to an acceptable level for use during normal times and/or when daylight contribution is prevalent. This level could be 33% or 66% if using a traditional design of 3-lamp troffers. Additional switches could be placed near the teacher’s desk for those times when more artificial light is required. The natural action for many people when entering a space is to turn all switches on at the bank of switches near the door, but the additional location requires the occupant to make a conscious decision to increase the amount of artificial light in the space.
- Attempt to reduce the amount of general illumination within a space and include task-based lighting as much as possible. In an office environment, carefully consider the task lighting at the desk and select fixtures that are flexible to accommodate varying ages of occupants with differing lighting needs.
When appropriate, these strategies can provide additional savings:
- Consider automatically dimmed fixtures for daylight zones and areas beyond (load shedding). These could be addressed individually or in groups. Either way, when lighting output is reduced automatically by properly commissioned lighting controls, maximum savings can be achieved because human intervention is not required.
- For spaces with audio-video systems, which could be as simple as a single projector and screen all the way to a sophisticated boardroom, use motorized shades as necessary to darken the room when the projector is used and to raise the shades when not in use. Occupants tend to avoid manually raising and lowering the shades, and instead leave them down, thus limiting the effectiveness of daylight contribution to the non-audio-video lighting control schemes.
The human factor
Since the widespread adoption of ever more stringent energy codes, as well as movement toward meeting the Architecture 2030 challenge of net zero or near net zero buildings, the ultimate goal is to minimize artificial lighting and human intervention of controls. However, recognizing there will be instances where both artificial lighting and human intervention are needed, the intent should be automation and task-based intervention when appropriate.
Providing owner training on what control schemes were provided, how occupants can adjust the lighting levels in their space, and how to maximize energy savings is of critical importance. Under ideal conditions, all spaces would contain ample natural daylight and automatic dimming controls to improve and reduce the lighting energy use in a facility. However, not all building owners can afford these control strategies. Additionally, educating building owners about the payback of more efficient lighting systems is difficult in some regions of the country due to low electricity rates, which greatly lengthens their return on investment. However, an integrated design team can design systems that maximize energy savings by having a coordinated effort between architectural, mechanical, lighting, and lighting control design.
Eric Kamin is a principal leader in DLR Group’s electrical engineering practice. He is skilled in developing specifications for primary and secondary power distribution, standby power systems, voice and data cabling systems, security systems, interior and exterior lighting design, and sports lighting design.