Sustainable Building Technical Manual - Etn-presco.net

❑ Improve optical control.Construction and retrofit projects can take advantage of new improvements in opticalcontrol by providing more light for the visual task and reducing glare or spilled lightwhile also enhancing energy efficiency. Reflectors within the fixture that direct and controllight into the space are now computer-designed and optimized for better efficiencyand control. Louver-finish options are also available for visual comfort and integrationinto a VDT-intensive area. Specifying fluorescent fixtures with heat extraction over thelamp cavity also improves fixture efficiency by allowing the lamp to operate at a coolertemperature and produce more light output.Lighting Contro l s❑ Provide effective lighting control.Among the greatest benefits of energy-efficient lighting are those resulting from effectivelighting control. The most basic function is time-of-day control to turn lights on and off.In addition:– Use occupancy sensors to detect when occupants are present in a space and to turn offlights when the space is unoccupied. Studies have shown that this results in a potentialenergy savings of more than 60 percent, depending on type of occupancy. Recentproject experience indicates that occupancy sensors are less costly to install than programmable-controlor dual-level manual switching. 3– Incorporate daylighting control strategies. Every building should provide the means tocontrol the electric lighting system in response to natural light from all envelopesources. Dimmable and stepped daylighting controls are two options that take advantageof the latest technology. Continuously dimmed control systems have the highestlevel of energy savings and user acceptance. They also offer additional energy-savingoperational strategies but have greater initial cost than stepped daylighting controls(see Chapter 9, “Daylighting”).– Incorporate lumen-maintenance controls that use photocells to continuously dim ballaststo maintain desired illumination levels and adjust lamp output in response tovariable outputs. Lumen output from light fixtures and lamps will be reduced over thecourse of their operating lives because of factors such as inherent lamp lumen depreciationand dirt accumulation on the fixture. Controlling light fixture energy, and thuslight output, overcome these factors to achieve energy savings.– Incorporate light-level tuning. Develop light-fixture layouts according to the layout ofworkstations or illumination criteria. This is preferable to the practice of designing fixturelayouts for visual appeal, uniformity, and standardization of lamps. Dimmableballasts allow lighting levels to be dimmed or “tuned” to the desired light levels,reducing energy use accordingly.A dditional Lighting Considerat i o n s❑ Use efficient exit signs.Modern exit signs use only one to six watts, compared to 40 watts for older signs. Theenergy savings can be sizable given the large quantity of exits and the need for continuousoperation of exit signs.❑ Consider improved task-lighting products.Inefficient incandescent and under-counter strip fluorescent fixtures are outdatedwhen compared to the products now available on the market, such as 15-watt compactfluorescent task lights. Issues such as luminance ratios (critical in VDT environments),veiling reflectance glare, and asymmetrical light distribution are important factors fortask lighting. High-performance task lights, compact fluorescent sources, asymmetricreflectors, and electronic ballasts should be specified. These measures can reduce energyuse by more than 50 percent. Some task lights are available with occupancy sensors