Yet, it is today’s state-of-the-art lighting technology that can deliver the greatest potential for energy savings in school buildings. The techniques range from daylight and occupancy sensors, to manual control and dimming.
Flexibility in Lighting Controls
In addition to classrooms, schools house a variety of multi-purpose spaces, including the cafeteria or “cafetorium,” gymnasium, auditorium and recreation center. Flexibility is a key theme in these spaces, as they often meet the needs of students during the day and the local community after hours and on weekends. Communities use their local school buildings for a wide variety of needs, including meetings, athletic activities, theatrical performances, concerts, presentations and as polling places. School districts building or retrofitting a K-12 facility should anticipate the full range of functions likely to take place there and incorporate a flexible lighting control system into the design.
Today’s building codes, such as ASHRAE/IESNA 90.1, Title 24 or IECC, require some lighting control. The degree of control required by each code varies. In some cases, code compliance might specify A/B switching in a space; in other situations the code might require four zones of passive daylighting with occupancy sensors.
Let’s take a walk through a typical school building, room by room, and assess how controls can fit into the design.
General spaces. For general spaces in a school—lobbies, corridors, restrooms, offices, maintenance areas, etc.—there are three important characteristics to consider when designing a lighting control strategy:
- Energy efficiency
- Life safety/security
- Architectural highlights
If a general space is only used at certain times during the day (or sporadically), automated controls such as occupancy sensors can ensure energy savings while the space is unoccupied. Occupancy sensors placed in hallways can be programmed so that fluorescent lights never fully shut off, only dim significantly, when the hallway or corridor is unoccupied so that energy savings can be realized while still maintaining the required minimum foot candle level for safety purposes.
In some general spaces, such as parking lots, stadium areas and athletic fields, time-clock control of the lighting is a great strategy to ensure efficiency. Time-clock control can be integrated into a lighting control panel or can stand alone on the system ensuring that lights are turned on/off to a pre-specified level at predetermined times. One of the most common uses of time-clock control is site lighting for parking and exterior areas around a school building. In these cases, most time-clock controls utilize an astronomical time clock that can be programmed to manipulate the light levels based on time of sunrise and sunset, as well the traditional 24-hour schedule.
Architectural highlighting can also influence the lighting control strategy. Time-clock control can incorporate specific lighting control solutions to highlight the architectural features of the school building without sacrificing energy efficiency.
Specialized spaces. Lighting control in specialized spaces—e.g., student common areas—helps create architectural detail and ambiance. Student commons have evolved a great deal over the decades and now accommodate a majority of social and educational activities.
These areas now serve as a signal of the school’s commitment to its students—and they are created to help make students feel
comfortable and welcome. As such, the lighting control strategy for the student commons area should include an intuitive manual control that allows the teachers and students to manipulate the light levels based on personal preference and the activity at hand.
Additionally, many student common areas incorporate a large amount of daylight, as well as shading to control glare. An effective way to maximize the efficiency of the daylit space is to incorporate daylighting controls with the electric lights. Photocells or daylight sensors can compensate for the varying degrees of ambient light in the common areas by switching or dimming the lights down throughout the day so the space is comfortable (not overlit) and is not an unnecessary burden on the school’s electric bill.
Multi-purpose spaces. Multi-purpose spaces are the most flexible in the building. They host numerous secondary functions, such as theatrical performances, concerts, presentations and other events. To meet the requirements of these areas, school officials must have the ability to completely control the environment—not just lighting, but sound, windows and other technologies that should all be integrated. Integration of all these features can be done through dimming and shading interfaces, as well as through traditional preset controls with interfaces that tie into the A/V system.
Classrooms. As classroom/lab spaces have become more dynamic—with computer workstations, traditional instruction, audio/visual systems and interactive white boards—they require greater levels of control. In addition, multiple classrooms can be combined to create a large space for grade-level instruction or multiclass projects. Manual control is the most commonly used classroom lighting control. Traditionally, manual control in the classroom, such as inboard/outboard switching, allows the lights to be turned on or off utilizing a wall control providing three light levels: Full On, Full Off, 50 percent.
Recently, dimming controls have made their way into the classroom space. Dimming allows the teacher to adjust the lighting to a precise level needed for the activity in the classroom. Providing classroom users with access to more than three light levels can not only help to improve the learning environment by increasing productivity, but dimming can also substantially reduce electricity consumption in the classroom and prolong the life of the light bulbs.
Occupant sensors are also used in many of today’s classrooms. Some building codes such ASHRAE/IESNA 90.1-2004 prescribe occupancy sensors in all classroom spaces. Most classroom occupancy sensors employ two technologies to control the lights. The first is passive infrared technology which senses occupancy by detecting the difference between heat emitted from the human body in motion and the background space. The second is ultrasonic technology, which senses occupancy by bouncing ultrasonic sound waves (32KHz- 45kHz) off objects in a space and detecting a frequency shift between the emitted and reflected sound waves.
Dual-technology occupancy sensors use both passive infrared and ultrasonic technologies for maximum reliability. These sensors help minimize the risk of false triggers (lights coming on when the space is unoccupied). Both ultrasonic and passive infrared technologies must detect occupancy in order for the light to turn on, while continued detection by either will allow the lighting to stay on.
Daylight sensors (or photo sensors) cause the lights closest to windows to dim or switch off as daylight pouring into the room increases. In most classroom situations, daylight harvesting combined with dimming the fluorescent lighting is ideal because throughout the day it is less distracting than daylight harvesting combined with switching zones. Normally, daylight applications divide the room into three to four zones. Each zone responds differently to the reading of the daylight sensor registers depending on its programmed required light level. Daylight harvesting is a great way to take advantage of an abundance of natural light in a space from windows, light shelves or skylights, without sacrificing any of the capability of the classroom on days or at times that natural light isn’t sufficient.
Ideally, a classroom will use combined control techniques (occupancy control, daylight harvesting and manual control) that offer a blend of automatic and manual control. This allows for the right lighting level for any given task and maximizes energy savings.
Lighting Controls In Action
The Arlington Heights, Illinois, School District 25 initiated a pilot project by installing a lighting control system in one classroom during the 2007-08 school year. Electricity consumption was reduced by 50 percent without sacrificing the quality of the classroom lighting, reports energy manager Robert Schultz. The lighting is calmer, not as glary and softer, according to the teacher who uses that room.
In Allentown, Pennsylvania, dimming controls and daylight sensors installed in two classrooms at the 124-year-old Grover Cleveland Elementary School have reduced lighting energy costs by 53 percent. During video presentations, the lights at the front of the classroom are dimmed to reduce glare and improve screen contrast, while a second group of lights positioned above the students remains bright enough to allow students to see their desks clearly and take notes easily. Daylight sensors measure the amount of natural light entering the room and dim the fluorescent lights accordingly. Greater student attention spans, motivation and attitude seem to be the result. According to principal Robert Wheeler, “The teachers tell me it’s now a distraction to use a regular classroom that doesn’t have this new technology in it. I can’t guarantee any individual student is learning more, but I can guarantee more students are learning.”Article courtesy of Lutron Electronics Co.