Achieving Energy Efficiency Through Effective Lighting Control
By: Jeff Park

As utility rates and operating costs continue to climb, focusing on reducing energy waste has never been more important. School administrators and facility managers are turning to energy-efficient technology, design, construction practices, and building operating practices in order to use energy wisely as they struggle to control their budgets and green up their campuses.

One area with excellent potential for savings is the electricity used to power campus lighting. According to the U.S. Green Building Council (USGBC), lighting accounts for more than one-third of the electricity usage in educational facilities. The good news is that in every school and on every campus there are numerous opportunities to implement lighting control strategies to save energy and reduce operating costs.

Lighting Control Basics
Lighting controls are used for many reasons: safety, code compliance, energy savings, sustainability, space aesthetics, and convenience. There are three underlying lighting control strategies that provide energy savings from automatic control of building lighting and may be used to achieve energy code compliance (required by most states for new construction projects, and for some lighting retrofit projects) and tighter operating budgets.

First, occupancy-based controls use an occupancy sensor to detect the presence, or absence, of occupants in a space and switch the lighting on or off as appropriate.

Second, daylighting-based controls use a photosensor to identify the level of daylight contribution and adjust the electric lighting downward, or off altogether, when appropriate.

Third, time-based controls use programming to turn lighting on or off at specified times on selected days and for planned events. 

Lighting control needs vary for different age groups and from school to school. For instance, in elementary and middle schools, the same teacher and students may occupy a specific classroom for much of the day, but the activities change throughout the day. In high schools, a variety of instructors and students may use a given classroom, but the activities remain similar from class to class. The best control solution for each space is one that ensures both occupant satisfaction and optimal energy savings.

Controlling Classroom, Administrative, and Restroom Spaces
For many classrooms, occupancy sensor control and bi-level switching provide the ideal combination of convenience for teachers and students coupled with energy savings. The sequence of operation is as follows: An occupancy sensor automatically turns on one-half or one-third of the lighting when someone enters the classroom. The occupants can then manually switch on a higher level of lighting, or they can turn all of the lights off. If the last person to leave the classroom does not turn the lights off manually, the occupancy sensor turns them off after a preset time delay. Circuiting the lights to allow individual lamps within a fixture to be controlled separately adds flexibility, providing different levels of lighting that can be used for different activities, and maximizes energy saving. With this type of classroom application, typical energy savings range from 35 to 45 percent.

The use of daylighting controls is an effective strategy for classrooms and administrative areas where the daylight contribution is substantial. In these spaces, daylighting controls can be added to the occupancy-based control to switch or dim the controlled lights when the daylight contribution reaches a specified level. Then, when daylight levels drop below the target levels, the photosensor sends a signal to return the electric lighting to a higher level of light. This extra level of control can increase energy savings an additional 10 to 30 percent.

As schools use high technology to educate students and operate the school, the control of plug loads (including printers, monitors and task lighting) is another opportunity for energy saving. Occupancy-based plug load controls help control the waste of standby power and turn off devices that frequently are left on all day, and even after hours.

School restrooms are another space suited to occupancy-based control. In large school restrooms, the best practice control solution includes installing a ceiling-mounted ultrasonic occupancy sensor set for automatic on-and-off operation. This type of sensor can effectively detect occupancy around partitions and other obstacles to provide the best coverage for the space. The occupancy sensor can also integrate exhaust fan operation with lighting control, turning both elements on when the room is occupied and off after the space has been vacated. The resulting energy savings can reach 30 to 60 percent.

Controlling Common Areas and Outdoor Spaces
For common areas (such as hallways, gymnasiums, and cafeterias) time-based control via a central relay panel with a programmed schedule is the best control practice. Lighting is turned on for each area at a scheduled time in the morning, remains on throughout the regular school day, and is turned off following completion of programmed events. A variety of strategies are used for after-hours control in different areas.

In hallways, supplemental occupancy-based controls can be used to turn lighting on when people are present at nights or on weekends and off after they leave. In gymnasiums, keyed wall switches or electronic time switches can be used to turn lighting on manually, temporarily overriding the panel. These overrides have a maximum duration of four hours before the panel will turn lighting off, unless the system is overridden again.

The best control practice in school stairwells, which require continuous lighting, is to use a bi-level stairwell lighting fixture with an integral ultrasonic occupancy sensor. The fixtures use just a little power in standby mode, providing the minimum light level required for codes, safety, user preferences, or security requirements during unoccupied periods. They provide full light output during occupied periods. This type of bi-level fixture-integrated sensor produces energy savings in the range of 50 to 80 percent.

Exterior lighting on school campuses for areas such as entries, walkways, and parking lots has traditionally been controlled using a combination of an astronomical time switch or a photosensor and time-based control panels. Lighting around entries is turned on at dusk, kept on all night for security, and turned off automatically at dawn. For walkways and parking lots, lighting is turned on at dusk and off at a scheduled time (perhaps 10 p.m., after activities have concluded for the day or evening). Some lights may be kept on all night for security. More recently, bi-level LED fixtures with integrated occupancy sensors have been designed for parking lot and walkway lighting. These fixtures provide low light output when outdoor areas are unoccupied and full light output when they are occupied. This enhances feelings of safety and security, while still saving energy.

Implementing Lighting Controls
The payback for installing energy-efficient lighting controls varies depending on the application, but it can be as short as a couple of years. In many areas, local utility companies have rebate programs for lighting controls, which help shorten payback periods.

Once controls have been installed, it is important to educate everyone who will be using the space about their function and operation. Properly educated users take better advantage of the flexibility afforded to them by lighting controls and are happier having the controls in the space. And, when they understand the green strategy behind the decision to install the controls, they become part of the solution, turning off unneeded lighting to save energy, cut costs, and reduce carbon emissions.

Jeff Park, LEED AP, CLEP, is the manager of sustainable market development at Watt Stopper/Legrand, www.wattstopper.com.