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Research Demonstrates Controls Can Help Reduce School Average Power Density to About Half of ASHRAE 2004/2007

Education has become a major construction market in recent years. In 2005, about $80 billion in spending made the K-12 and higher education markets the largest nonresidential segment, which held in 2006 ($85 billion) and 2007 ($100 billion) and will likely hold in 2008-09.

And it’s a good thing, too. Each year, more and more students are using facilities that are getting older and older, and using them differently than previous generations.

Figure 1. Lighting typically represents 30-40% of school utility costs.

Consider that in the fall of 2006, nearly 50 million students began using more than 385,000 school buildings; the number attending public elementary and secondary schools had risen 24 percent since 1985. According to the U.S. Department of Energy, just a few years before—in 2003—more than 60% of all school floorspace had been built before 1980, and 40% of that space had never been renovated. And students are increasingly using whiteboards, computers, Internet and multimedia, making classroom design as sophisticated as hi-tech corporate board rooms and conference spaces. To top it off, energy codes are becoming more and more restrictive on schools: A maximum power density of 1.6W/sq.ft. for classroom is prescribed by ASHRAE Standard 90.1-1999/2001, 1.4W/sq.ft. by ASHRAE 90.1-2004/2007, and 1.2W/sq.ft. by California’s Title 24-2005.

So the public and private sectors are spending record funds on school construction, renovation and modernization. Demand for lighting quality and flexibility is increasing to keep up with new visual needs, and the amount of power available for lighting is decreasing. This implies that tough design choices must be made; as the average school building built today will last the next 40-50 years, these choices are critical.

The high-performance schools movement, promoted by organizations such as the Collaborative for High Performance Schools, provides guidance on how to achieve schools that have good lighting, indoor air quality, temperature and humidity and acoustics, and minimized energy consumption, resource allocation and costs. Reducing energy costs is welcome to most schools; lighting alone typically devours 30-40% of school utility expenditures. But is lighting up to the task? Can today’s lighting technology provide a quality visual environment with the kind of flexibility required in high-end conference rooms, while minimizing energy costs and meeting tough energy codes?

The New York State Energy Research and Development Authority (NYSERDA) took this one step further by basically asking what’s the best value in school lighting, with value being defined as the most appropriate lighting for the lowest energy cost?

NYSERDA sponsored a demonstration project featuring a new Integrated Classroom Lighting System (ICLS) created by Finelite, Inc., a fixture manufacturer, installed as a retrofit into 28 existing classrooms at seven schools and universities. The Lighting Research Center (LRC) assessed teacher and student satisfaction.

The result is a design template demonstrated to satisfy audio-visual needs and improve teacher and student satisfaction while reducing lighting power density to an average 0.73W/sq.ft., nearly 50% less than ASHRAE 90.1-2004/2007. Although Finelite optimized the design into an engineered system integrating the company’s light fixtures with state-of-the-art lighting control strategies, the template, if properly designed, can be treated as open source with suitable products from a wide range of manufacturers.

The design typically is composed of two rows of direct/indirect pendants with a wallwasher whiteboard fixture mounted on the main teacher board. The fixtures are placed parallel to the window, with the rows spaced 14-15 ft. apart.

ICLS template

Figure 2. The ICLS template.

Legend:

1) Two rows of two-scene indirect/direct luminaires mounted perpendicular to the main teaching wall (parallel to window wall) and spaced 14-15’ apart.

2) A dedicated luminaire is used to illuminate the whiteboard on the main teaching wall.

3) Teacher control is placed at the front of the classroom. For easy teacher access place controls within 6 inches of the whiteboard.

4) Sensors are placed in the center of the classroom. Sensors always include occupancy and daylight harvesting is added where appropriate.

5) A master ON/OFF switch is by every door to the classroom.

Each fixture uses three high-performance (3100-lumen) T8 lamps—with one inboard lamp providing the downlight component and two outboard lamps providing both uplight and downlight. The inboard lamp and outboard lamps are electrically separate so that they can be separately controlled.

The fixtures are integrated into a lighting and control system featuring a ceiling-mounted dual-technology occupancy sensor placed between the rows of pendants, a master switch at the door and a “teacher control center” located near the main teaching board, which features:

  • A “Whiteboard” switch that turns the wallwashing fixture mounted on the main teaching board ON and OFF;
  • A “General/AV Mode” enabling the teacher to switch between General mode (downlight OFF, uplight/downlight ON) and A/V (and reading) Mode (downlight ON, uplight/downlight OFF; and
  • A “Quiet Time” switch that overrides the occupancy sensor for one hour, keeping the light on during long periods of occupied non-movement such as standardized testing.
teacher control center in ICLS

Figure 3. The “Teacher Control Center,” which was mounted 6 inches from the main teaching board.

Teachers were also able to access another option, A/V Dimming Mode, which allowed them to turn on and then dim the inboard lamp providing the downlight component. This required a dimmable ballast. All controls were connected via a CAT-5 plenum-rated low-voltage line with plug-and-play connections.

Optionally, a photosensor can be added, adjusting light output based on daylight availability.

Hunter High classroom with the lights on General Mode

Figure 4. Hunter High classroom with the lights on General Mode.

Hunter High classroom with the lights on A/V Mode

Figure 5. Hunter High classroom with the lights on A/V Mode.

Watt Stopper/Legrand provided off-the-shelf power and auxiliary relay packs to accomplish the fixture switching, the occupancy sensors with the customized Quiet Time feature, and switches for the teacher control station (through its sister company Pass & Seymour Legrand). Click here to see an interview with Jon Null, Director of Marketing for Watt Stopper/Legrand, about this project, or scroll down.

Results:

  • Because all three lamps cannot be ON at the same time, the maximum lighting power density is capped at about 0.8W/sq.ft.
  • The switching controls reduced average lighting power density to 0.73W/sq.ft., about half of ASHRAE 2004/2007 and about 40% less than Title 24.
  • The LRC found that teachers generally preferred ICLS to the previous lighting system and that students also rated it favorably.
  • The system was installed for $1.83-$2.29/sq.ft.; options such as daylight switching and a third fixture row to increase uniformity, add to the cost).
  • The LRC found that installers generally characterized the system as “easy to install.”
  • The design is suitable for both new construction and retrofit.
ICLS energy savings

Figure 6. The combination of energy-efficient lighting and integrated controls reduce average lighting power density to an average 0.73W/sq.ft. Click on the image to see it enlargened in a new window.

Direct/indirect lighting and separately controlled fixtures for general and main teaching board lighting are considered best practices by the Collaborative for High Performance Schools. Optimizing this approach as a system with integrated controls maximizes its utility for A/V functions while minimizing energy consumption. Many of the research findings of this study are being incorporated into best practice developed by the Collaborative as well as the U.S. Green Building Council’s LEED for Schools green building rating system, according to LRC.

For more information about ICLS, including the complete reports on the California Energy Commission and NYSERDA demonstration projects, click here.

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