Sustainable Building Technical Manual - Etn-presco.net

CHAPTER 9Day l i g h t i n g★ S I G N I F I CA N C E .Daylighting is the practice of bringing light into a building interior and distributing it ina way that provides more desirable and better-quality illumination than artificial lightsources. This reduces the need for electrical light sources, thus cutting down on electricityuse and its associated costs and pollution. Studies substantiate that daylighting createshealthier and more stimulating work environments than artificial lighting systems andcan increase productivity up to 15 percent. 1 Daylighting also provides changes in lightintensity, color, and views that help support worker productivity. Surveys have shownthat 90 percent of employees prefer to work in spaces with windows and a view to theoutside. 2 In one study, 75 percent of office and factory workers stated that daylight providesbetter quality illumination than artificial light. 3AuthorLoren E. AbrahamDaylighting significantly reduces energy consumption and operating costs. Energy usedfor lighting in buildings can account for 40 to 50 percent of total energy consumption. Inaddition, the added space-cooling loads that result from waste heat generated by lightscan amount to three to five percent of total energy use. Properly designed and implementeddaylighting strategies can save 50 to 80 percent of lighting energy. 4Greater use of daylighting can also provide advantages for the environment by reducingpower demand and the related pollution and waste byproducts from power production.Lighting—and additional building cooling requirements from lighting—use an estimated20 to 30 percent of total United States energy production. 5 About three-quarters of thisamount is used to light commercial and industrial buildings. If extensive daylightingmeasures achieved only a 40 percent lighting energy savings, total national electricityconsumption would be reduced by six to nine percent. 6 In addition, the greatest savingsfrom daylighting occur during periods when sunlight is most intense, which coincideswith periods of peak demand for heating, ventilating, and air-conditioning (HVAC) andrefrigeration loads. Therefore, wider use of daylighting would reduce both the need fornew peak demand capacity and overall power demand.