Location-Specific Lighting Efficiency Strategies in Schools
Schools represent a target market for a slew of innovative lighting efficiency strategies. First off, the Department of Energy estimates about 30 percent of electricity consumed by a typical school is for lighting alone. Because of the coincidental heat generated by outdated lighting fixtures, even more electricity is used to run air conditioning units. Why not redirect wasteful utility expenses toward the general upkeep, health, safety and educational adequacy of school buildings?
If your school hasn’t updated its lighting in the past five years, a lighting retrofit could present an opportunity to reduce lighting expenditures by 30 to 50 percent. What’s more, a lighting retrofit can actually reduce cooling costs as well—by 10 to 20 percent. Based on information culled from a report produced by the California Lighting Technology Center at the University of California, Davis, here is a brief overview of lighting efficiency strategies that work well in specific locations.
For restrooms, the single most effective upgrade is the introduction of occupancy sensors. Because restrooms are typically vacant for more hours than they are in use, shutting lights off during vacant hours using occupancy sensors can yield an outstanding payoff. Lighting controls can turn off lights completely or dim them to 50 percent depending on the size of restroom or locker room. One key study developed for the Illuminating Engineering Society (IES) in 2000 found that installing occupancy sensors in public restrooms resulted in energy savings of 73 to 83 percent.
Library lighting is more complex, as it requires general lighting as well as task lighting tailored to specific activities. Typical library areas, including computer rooms, storybook areas, book stacks and lending counters, each require both horizontal and vertical illuminance considerations. Control recommendations for libraries include utilizing a continuous dimming strategy, optimizing daylight opportunities, increasing surface reflectance and installing occupancy-based dimming controls. One case study found that the installation of new wireless controls incorporating daylight harvesting, occupancy sensing, scheduling and tuning reduced total lighting energy use by an estimated 36 percent.
In gymnasiums the key lighting issues surround that high light output industrial fixture used for indoor sports activities, including video broadcasting — the ubiquitous high bay luminaire. For years static (single-level) high-intensity discharge (HID) light sources have been utilized—usually with metal halide (MH) lamps. But HID light sources, with their long startup cycles, create reluctance by faculty and staff to turn lights off—even for long periods of inactivity. This re-strike lag time creates enormous waste in school gymnasiums by default, as lights tend to be left on for long periods of time.
The first order of business for gyms is to replace old, HID luminaires with dimmable, energy-efficient, “instant-on” luminaires. This step alone will dramatically improve both energy efficiency and functionality. For extra measure—and savings—equip these luminaires with occupancy-based controls as well as manual controls that support multiple light levels for different functions. Choosing a higher color temperature luminaire with low flicker will also help address video broadcasting requirements.
Hallways and Stairwells
Similar to restrooms, occupancy patterns in hallways and stairwells are highly intermittent throughout the day. Plus, these areas are largely vacant both during and after school hours. This context is a setup for the success of occupancy-based lighting controls. It’s also required, per California’s 2013 Building Code Title 24, Part 6 standards. Under the new law, lights in corridors, stairwells, and certain library book stack aisles should automatically dim by at least 50 percent of full lighting power when vacant.
Using bilevel, occupancy-based lighting controls in corridors can reduce lighting power during unoccupied periods by 46-65 percent according to UC Davis study while also automatically restoring full light output when occupants enter the space. This offers a twofold bonus: large savings for educational institutions, and no compromise on safety, security or visual comfort.
This is where it all comes together – classrooms are perhaps the most important and most complex area to develop lighting efficiency strategies for in schools. The fluorescent strope effect of antiquated T-12 has infiltrated most classrooms and continues to waste unnecessary energy. The International Illumination Society of North America suggests that lighting should be diffused and comfortable while also bright and task oriented, as visual performance is required on both the horizontal top of a desk and the vertical face of a whiteboard. Removing older magnetic ballast powered T-12 for high efficiency electronic powered lighting technologies will immediately save money and provide a crisp, clean light for students.
Lighting flexibility by the use of dimming or scene controls can make tremendous impact on visual comfort in the classroom. The utilization of dimming controls for presentations, occupancy sensors to turn lights off before and after class sessions and photocell controls to capture daylight harvesting areas are simple but excellent lighting efficiency strategies to reduce costs. The installation of pre-programmed scene controls adds another layer of energy savings and is a powerful tool for instructors to adjust lighting to fit a wide variety of activities.