Sustainable Building Technical Manual - Etn-presco.net

❑ Match the quality of light to the visual task lighting requirement.The quality is more important than the quantity of light delivered to the visual task. Ahigh-quality lighting solution requires less light to yield the same visual performance.Light quality involves the following factors:– Luminance ratio limits;– Veiling reflections (reflection of light source in visual task);– Reflected glare;– Shadows;– Color; and– Intensity.For example, indirect lighting systems that reflect light off the ceiling can produce alow level of uniform, low-glare light that is sufficient for VDT lighting needs, withenergy-saving results.❑ Improve lighting design and energy efficiency by performing several key activitiesin the early phases of architectural space planning.– Coordinate the lighting plan (reflected ceiling plan) with furniture layout. Areassuch as walkways or service spaces can “borrow” light from adjacent work areas.– Coordinate daylighting to be available in spaces such as walkways, lounges, and areasintended for recreation and other public uses where the variation of color, intensity,and direction of light are desirable. In other spaces such as offices and conferencerooms where lighting quality is important for performance of visual tasks, daylightingneeds to be controlled properly for brightness and direction of light.– Where possible, group occupants with similar work schedules together. This allowslighting in other areas to be turned off during unoccupied periods.❑ Improve room-cavity optics.The use of smooth, high-reflectance surfaces can greatly improve the efficiency of naturaland artificial lighting. For example, use:– Light- or neutral-colored surfaces to improve reflected light;– Fine-fissured ceiling tiles with a smooth, reflective surface;– Light shelves for introduction and control of natural light; and– Low office partitions to avoid shadows and dark zones.Lighting Fixtures and Lamps❑ Specify efficient lamps for the intended use.Choices in lamps have greatly expanded during the recent revolution in lamp technologyto include:– T8 fluorescent lamps;– Compact fluorescent lamps;– Lower-wattage, high-color-rendering HID lamps;– Compact reflector HID lamps (such as PAR30 and PAR38);– Halogen lamps with infrared reflectors; and– Sulfur bulbs.❑ Use electronic ballasts.One of the biggest improvements in fluorescent lighting efficiency over the past fewyears has been the introduction of reliable electronic ballasts, which are 10 to 20 percentmore efficient than the most efficient magnetic-coil-type ballast. Electronic ballastsenergize lamp phosphors at a higher frequency which eliminates flicker and offersbetter light quality while using less energy. Selecting electronic ballasts with the appropriatecapacity of light output (known as the “ballast factor”) makes it possible tomatch light output from fixtures and lamps to the specific design requirement.Dimmable ballasts (stepped and continuously dimming) provide a significant increase inefficiency when used in conjunction with the control opportunities discussed below. Thelatest ballasts have substantially reduced induced harmonics, one of their previous drawbacks,and high power factors. The use of electronic ballasts with HID lamps has beenfound to limit the color shift often inherent in HIDs and standard magnetic ballasts.