School lighting strategies can cut energy use and save money.
Cut energy use and save money with school lighting strategies.
Old, flickering fluorescent tubes and heat-shedding incandescent bulbs should be a thing of the past, but in many schools, they’re an inefficient, underperforming part of the present.
It doesn’t have to be this way. The constant evolution of lighting technology results in lower costs and better light quality for a variety of lamp types. After a little homework, you can make an educated decision about improving the lighting in your facility.
How Do You Use Your Lighting?
Start by examining the current state of your facility. Take a look at electronic equipment, occupant behavior, and any other factors that affect energy use. Where is the building’s power density concentrated? When, where, and how are the lights used? What are the ceiling and plenum heights throughout the school?
As you conduct your walk-through, note problems and spaces that require improvement. Look for opportunities to create a visually comfortable environment as defined by the Illuminating Engineering Society of North America (IESNA):
- Provide views to the outside, which allow the eye muscles to relax as they focus on the distance.
- Control window luminance to avoid glare.
- Ensure that the angle between any source of high luminance and principal sight lines is as large as possible.
- Avoid high brightness contrasts.
- Place sources of high brightness against a bright background to reduce visual discomfort.
- Replace recessed parabolic or lens fixtures with pendant-mounted indirect or direct fixtures.
After you’ve examined the school’s suitability for retrofit projects, balance the benefits of these improvements against your budget and determine which projects offer the most advantages with the smallest payback period.
Introduce Natural Light
Daylighting means more than opening the window shades. Aim for balanced, glare-free light from at least two directions that provides enough light for the tasks conducted in the space and allows occupants to turn off the electric lighting system for part of the time.
A few simple strategies will help you add daylight to school spaces or maximize what’s already available. For example, south-facing roof monitors, a toplighting solution with vertical glazing that offers more shade in the summer, are a great match for gyms and cafeterias because these spaces tend to have shallow or no roof cavities and fewer ductwork conflicts. The frequent use of these spaces offers the potential for steep savings. Save the installation until you’re revamping your roof to make the project even more economical.
“In a gym, everything in the ceiling is exposed, so if you have ductwork you know where it is,” says Michael Nicklas, president of architectural firm Innovative Design and a daylighting expert on ASHRAE’s K-12 committee. “The gym is also used the most in almost every school, starting early in the morning and often on Saturdays and Sundays, so it’s typically the space that has the fastest payback.”
When retrofitting classrooms, toplighting is a much tougher approach, Nicklas adds. Windows located close to the ceiling offer real possibilities, however, especially when you apply high-performance glazings or replace assemblies from the 1950s and 1960s. Many schools from that era have windows with excessive glazing, Nicklas adds, so replacing high glass areas with improved glazing and reducing the lower view glazing will result in significant comfort improvement and energy savings.
“Use some of the more advanced glazings like nanogel between the glass panes. That will provide you with a glare-free visible light transmission of 20% and R-values up to R-20,” Nicklas says. “The cost used to be so high that even two to three years ago it wouldn’t be a practical renovation strategy for a school, but now the price is starting to drop. At current costs, glazing systems with 20% visible light transmission and R-20 are pretty good.”
Optimize Artificial Lighting
Next, focus on artificial lighting. Relamping alone won’t address occupant behavior or offer more control, but upgrading to high-efficiency lamps and fixtures will certainly cut down on your energy costs. Paired with the right controls, a relamping project is a force to be reckoned with.
“Depending on the application, you could choose from a number of different fixtures,” explains Jim Messner, electrical engineer for SHP Leading Design. “Our most common retrofit application is for a gym or multipurpose room with HID or metal halide fixtures. Those have poor energy and controllability performance, and their light output really degrades over time. In that application, we’d replace it with a high-bay fluorescent fixture – a linear T8 or T5 has better controllability, puts out more light, and is quite a bit more energy-efficient.”
At James Monroe Elementary, a new K-5 school in Everett, WA, administrators took a different tack. Monroe, which serves 470 students, replaced seven smaller hexagonal buildings that opened in 1969. Its grand opening for the second half of the 2011-12 school year heralded the arrival of the first public school in the U.S. to depend almost entirely on LEDs.
The technology’s value became clear after the district test-drove indoor LED applications in two renovation projects – turning Heather Wood Middle School’s former wood shop into two classrooms and retrofitting the school board’s meeting room. The results, says director of facilities and planning Hal Beumel, speak for themselves.
“These were basement classrooms and initially no one wanted them,” Beumel explains. “They turned out to be the most popular classrooms in the school, mainly because of the adjustable lighting levels. For fewer watts per square foot, we provided a higher level of lighting with a better CRI.”
The Everett School District spent about $100,000 to install LED fixtures and dimmer switches in the structure, believing the 10-15-year payback, reduced replacement timetable, and estimated 25% cut in energy spending far outweighed the higher upfront cost. Classrooms were outfitted with durable color-correcting lamps controlled by occupancy sensors and dimmer switches. LEDs also provide all exterior lighting, including dual-level lamps in the parking lot that brighten when their motion sensors are triggered.
“You have to be careful about what fixtures you specify. There are a lot of them out there that just won’t work, so you have to be particular,” Beumel advises. “These have a very high CRI, so the colors in the classroom are almost like daylight. One teacher said that even on gray cloudy days here in the Seattle area, where there are lots of them, the classroom seems like a sunny day. It makes a huge difference.”
Monroe’s gym and all spaces that require indirect lighting, such as the library and some hallways, use traditional fluorescents because the highly directional LED products were not yet ready for those applications. High-output fluorescent lamps are an ideal replacement for metal halide fixtures in gyms and indoor sports areas, says Craig Kohring, project manager and CFO of MDA Engineering and a member of ASHRAE’s K-12 committee.
“If metal halide fixtures get turned off during the day, they don’t refire, and you’ve got to go through a 10-minute cooldown and a 5-minute warm-up time for them to come back to full brightness. Consequently, they’re left on all day,” Kohring explains. “If instead of a 400W metal halide fixture, you put in a new four-lamp T5, you have about half the wattage with the same light output. You can turn those off for an hour or two when the gym is empty and save all of that wattage and energy.”
Regain Control of Illumination
If nothing else, install occupancy sensors or timers wherever you can. Many older schools have spaces, such as janitor’s closets, with one or two incandescent lamps that stay on all day. Adding a single sensor to one of those small spaces can save a considerable amount of money, and you can gradually install a few sensors at a time as your budget allows.
“The cost of an occupancy sensor to go in the wall is not a lot of money compared to what you’ll save,” says Kohring. “For a small space, you could do it for $25 to $50 and have your maintenance guys install it.”
Don’t stop after installing individual controls, however. To cut energy use further, tie some or all of the lighting into a building- or district-wide control panel that allows you to monitor energy use, spot underperforming or failing fixtures, and turn off unnecessary lighting remotely.
James Monroe Elementary uses its unified lighting control system for hallways, large assembly spaces, and exterior lighting because Washington building codes require individual motion sensors for classrooms. In addition to tying in classroom lighting when permitted, other facilities could use this technology to test the efficacy of additional energy-cutting strategies.
The data can also help encourage occupants to change their behavior. Consider a digital display in one of your building’s common spaces that shows energy consumption by grade, floor, or wing. Teachers can capitalize on this data to teach students about conservation or start a contest to see who can reduce their energy use the most.
“Monitoring systems that identify energy consumption by individual key circuits cost a lot. You’re looking at $2 to $3 per square foot added to the initial construction cost, which is the downside,” Nicklas explains. “It’s tough for schools to bite that bullet, but boy, is it valuable. We designed two middle schools based on the same prototype – they’re pretty much the same, but one performs about 10% better. If monitoring had been implemented into these schools, it would have enabled the principal to say ‘This wing is using more energy than the other wing. Let’s find out what’s going on here.’”
Adjust Other Building Systems
Finally, re-evaluate building systems and equipment – they may need adjustment to perform well with your new lighting system. A retrofit project involving high-performance fluorescents or LED fixtures, for example, should result in less heat generated by the lighting system, so your chiller shouldn’t work as hard as it used to – if it does, something is wrong.
If your budget allows, it’s ideal to replace or upgrade multiple systems at once, says Messner. This way, you’ll likely end up with more efficient equipment and building systems that work well together.
“There’s a lot of energy waste in older schools,” Messner adds. “If you do a renovation and replace all the light fixtures, at some point, you’re going to have to replace the HVAC system. Doing one before the other could compromise the new systems.”
Bundling your improvements may cost more up front, but it can dramatically reduce the payback period, Nicklas says.
“If you want daylighting, you’re going to see that daylighting, lighting, and mechanical systems are all intertwined,” Nicklas explains. “If you were to reglaze a south-facing classroom on the first floor, you might end up with a 10-15-year payback range. But if you were to look at daylighting plus lighting, it may drop by a couple of years, and if you look at daylighting, lighting, and mechanical systems, it may drop down a couple more years.”
Ultimately, total lifecycle costs will play a prominent role in how you construct a more efficient lighting system. Look past the initial cost – maintenance, lighting level flexibility, durability, and other factors should all factor into your decision.
“You really want an integrated approach that looks at the maintenance costs, energy performance, and quality of light,” Messner says. “If it’s done right, you shouldn’t have to compromise on lighting quality or payback.”
Janelle Penny (firstname.lastname@example.org) is associate editor of BUILDINGS.