Bright light, brighter students
Good school lighting provides myriad benefits—including lower power bills and boosted test scores—but effective design requires smart planning.
Our Roundtable Participants, from left to right:
- Robert H. Altman, LC, NCQLP Lighting Certified Electrical Designer, Loftus Engineering Inc., Indianapolis, Indiana
- James R. Benya, PE, FIES, FIALD, LC, Principal, Benya Lighting Design, West Linn, Oregon
- Tim Hill, PE, LEED, AP, Electrical Discipline Director, Senior Associate, Fanning Howey, Celina, Ohio
- Gersil N. Kay, IESNA, President, Conservation Lighting International Ltd., Philadelphia, PA
CSE: What types of lighting do you suggest for K-12 school buildings?
Robert H. Altman: I would suggest to use a linear indirect fixture with an efficiency of 90% or greater.
James R. Benya: Considering the economic times as well as climate change, I feel that almost all lighting systems should use T5 or T8 lamps. For classrooms, the two-scene Integrated Classroom Lighting System described in LEED for schools and the Collaborative for High Performance Schools (CHPS) Guidelines is almost all that I use today. For the rest of the lighting, such as hallways and bathrooms, it still pays to use the T5 and T8 lamps as much as possible.
Tim Hill: Fixtures using linear fluorescent T8 lamps are still the dominant type used for interior lighting. Lay-in troffers and suspended linear direct-indirect fixtures are used about equally.
CSE: Describe a school project you were recently involved with, and how you integrated lighting and daylighting.
Hill: At McPherson Middle School in Clyde, Ohio, we used roof monitors to introduce daylight into classrooms. Vertical baffles were installed in the monitor shaft to reduce glare from direct sunlight and create the illusion of a ceiling plane.
Benya: The best one so far is the Redding School for the Arts, currently under construction in California. The architects and I worked closely to develop the perfectly daylighted school, with mostly north facing windows in classrooms and light from the south through a tensile structure and high wall clerestory windows. There is almost no east or west facing glass. The classroom lighting system I described above is used with a full digital lighting control system employing daylight sensors, motion sensors, and wall switch dimmers, and it integrates lights and window shades to absolutely minimize electric lighting use. The school is designed to be Zero Net Energy, by the way, so any energy that can be saved is a priority.
CSE: Now that ASHRAE’s Advanced Energy Design Guides for K-12 School Buildings has been available for a couple of years, what changes have you seen in lighting and energy usage?
Benya: The AEDG is a good document but for lighting and daylighting; it is about the same as the CHPS recommendations. I like CHPS a little better because the daylighting recommendations do a better job of allowing for architectural creativity and unique solutions. Both are helping architects and engineers design schools that use about half of the energy of just 20 years ago.
Hill: Energy usage continues to decrease. Ten years ago, if 50 ft-candles was good then 60 ft-candles was better. We’ve changed that mindset. We think it is important to design to the specific task being performed per the IES Recommended Practices. Permitted lighting power density continues to decrease as better lamp and ballast technology becomes available.
CSE: What impact has the U.S. Green Building Council’s LEED for Schools had on lighting design?
Hill: In addition to promoting energy efficient designs, LEED has increased the awareness of what healthy lighting is by promoting daylighting and direct views to the exterior. Also, I think architects and interior designers are more aware of how decisions they make can affect lighting.
For instance, how increasing the ceiling height at the window wall can increase daylight penetration into the classroom. And of course, lightly colored finish selections increase reflectance values.
Gersil N. Kay: Overly enthusiastic energy conservation without an increase in productivity, safety, and personal comfort will inevitably fail. People will always find ways to circumvent unwanted or impractical restrictions, negating the expected goals.
CSE: Daylighting causes both glare and heat. How can lighting designers offset these?
Benya: Daylighting is actually two to five times more energy-efficient than electric lighting. Properly designed daylighting that uses light from the sky dome and minimizes direct sunlight can provide more light with less cooling load. Unfortunately, most architects, engineers, and lighting designers don’t yet have the skills to design daylighting this well, and most daylighting designs simply introduce too much light, and then there is often too much heat. I’ve designed the daylighting (and lighting) for schools from Seattle to Tucson, and they are much more energy efficient than conventional schools.
Hill: We’ve used vertical baffles in roof monitors and exterior light shelves depending on the daylighting strategy. One interesting technology we’ve used is called a tubular daylighting device. An acrylic dome about 2 ft in diameter gathers light and transmits it through an aluminum reflective tube into the occupied space. The tube terminates in a variety of diffusers. A shutter using standard 0–10 V lighting controls is available to “shut off” the daylight when needed for audiovisual presentations.
CSE: According to “Daylighting in Schools,” a study of 21,000 students done in 1999 by the Heschong Mahone Group, students’ test scores improved up to 26% with appropriate daylighting. In your experience, what’s appropriate?
Benya: HMG actually repeated and updated their findings in 2003 in work funded by the California PIER program. They corroborated their earlier findings, except that they concluded that rooms with a view were slightly better than rooms with only skylights. When you combine the epigenetic and circadian health benefits of naturally lighting interior spaces, daylighted classrooms should be a no-brainer. Healthier students with better test scores = happier teachers = lower energy cost. Why would schools be designed any other way?
Recently, I have joined forces with Deborah Burnett, ASID, a national expert in epigentic deigns and the design of healthy environments to provide integrated consulting and teaching services to help design these healthier, happier, more efficient environments. We see the combination as an evolving field in this decade, now that the physiological impacts have been related to principles in physics.
CSE: What capabilities do lighting controls offer? What should engineers look for when specifying controls?
Altman: The capabilities the lighting controls offer include the adjustment of lighting for various scenes and to conserve energy. An example of adjustment to the lighting would be when a teacher uses an overhead projector for slide shows or notes. The lighting control system can be designed to turn off the front row of lighting and also dim the remaining lights to highlight the projection screen. Examples of energy conservation could be something as simple as an occupancy sensor or as elaborate as daylighting harvesting.
One item that I feel is lacking is the specification into one specialized system. If appropriate, the designer/engineer should try to find a couple of concepts that are similar. The other item would be the software for the control system. You want something that can talk to the BMS system of the building.
Hill: Look for manufacturers who offer great, local support and train their installers how to commission a system. Once the building is complete, the controls cannot distract from the educational tasks in the classroom. Occupancy and daylighting sensors must not cycle lighting so frequently as to disrupt the classroom or burden facilities personnel with maintenance calls to readjust the system.
CSE: What are the biggest barriers to incorporating lighting controls in schools?
Altman: The costs of lighting controls seem to be a big barrier. Since most schools are on a budget they try to get the most bang for their buck, so lighting controls and lighting are usually the first things to get scaled back during budget issues.
Benya: Cost, cost, cost. Contractors have been trained to cut cost and usually without significant regard for energy efficiency. Also, many electricians lack the expertise needed to install and commission modern control systems. But this too is changing. Southern California Edison is working with NECA and IBEW, for example, to develop contractor and electrician education in controls to help make them more cost-effective.
Kay: Good lighting should be created by experienced professionals. In lighting, one size/type does not fit all. It is not a DIY activity; otherwise it is like being your own brain surgeon—while slicing and reading, you could die of a misprint.
CSE: What code issues do lighting designers run into, and how can they overcome them?
Hill: Energy code issues are making the news, but compliance with energy codes can be made by meeting lighting power density and specifying controls. The wrong lighting fixtures and inappropriate controls can be included and still meet energy codes. The lighting designer needs the training and experience to know the correct fixtures and controls to specify.
In addition, building codes related to emergency egress lighting are as challenging because they vary more with jurisdiction. It is important to know what version of the code applies to the project, and in many cases, how the local authority interprets the same code. For instance, the IBC requires occupancies which require two means of egress to include emergency lighting. However, some jurisdictions say that includes exterior grandstands while others do not.
Benya: Code issues don’t seem to be a major issue right now, the exception of course being those who don’t want to have to deal with energy efficiency. Looking forward, the biggest new obstacles I foresee include excessive requirements by UL for LED lighting. LED is inherently low power, low voltage, and low heat. I hope UL recognizes this and does not impose greater restrictions on LED than it presently has on regular lamps.
CSE: Anything to add?
Benya: Cost will tend to limit the use of new and evolving technologies. For instance, we recently proposed to light a gym at Tucson High with daylight. There is adequate daylight in Tucson—and then some. For lighting the gym, we proved that skylights were three times more energy-efficient than a PV system and electric lights, and do not increase the cooling energy use.
However, without a rebate from the utility company, TEP, the payback period of skylights is presently about 10 years. Many school districts would not make this investment—and would not buy the PV system, either. But TEP is presently considering awarding the same efficiency rebate as it would have for the required PV system to light the gym, making the payback period a bit less than 5 years. The project has been mostly built and lighting measurements are exactly as predicted.