Consulting-Specifying Engineer - May 2008 - (Page 25) This classroom at Fay Herron Elementary School in North Las Vegas, Nev., has both natural light and artificial light, provided by the combination of solar reflective tubes and lighting control keypads and light-level sensors. All photos: Square D/Schneider Electric front of the room, but students in the back of the room can still take notes. The light of day Lighting designers can’t discredit the benefit of good daylighting. 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. But what’s appropriate? If every school could face north and receive even, diffused light throughout the school year, this whole daylighting discussion would be pointless. But not every building can be sited that way, and schools typically are in session during the darkest, dreariest days of the year. Appropriate options abound, but many lighting designers forget that less can often be more. While side (window) lighting is beneficial, it’s often not the best type of Tricks of the trade Tom Foster, PE, president of Professional Design Associates Inc., Henderson, Nev., shares his top five lighting design tricks. These tips come from his years of experience, and his work at Fay Herron Elementary School in North Las Vegas, Nev., which includes both tubular skylights and a lighting control system. 1. Solar light levels should be based on a median level of lumen output for the device used based on the project location. An analysis can be run for seasonal minimums and maximums to find the range of solar contribution. 2. The controls should have an adjustable response delay so the short-term transients in solar light levels (due to fast-moving clouds or aircraft shadows) do not unnecessarily switch the lights on/off. This is less of an issue if a dimming system is used, but very important for switched systems. Nescience switching is very disruptive in the classroom. 3. If the facility uses rooftop air conditioning units, or other significant rooftop equipment, perform a shadow study to optimize solar device roof locations. 4. Have strict drawing and specification requirements for solar device locations such that any relocation due to structural, piping, or ductwork is first coordinated with the lighting designer. 5. Classrooms usually require the ability to darken the rooms for presentations. This requires a method to close the solar devices. Use a product with a proven track record of interfacing with the control system. Fay Herron Elementary School has solar reflective tubes built into the roof of one of the buildings. A shadow study was performed prior to their placement to ensure light was not blocked by the rooftop air conditioning unit. Consulting-Specifying Engineer • MAY 2008 25
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