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Unformatted text preview: Statistic on Lighting o Accounts for 20 to 25 percen of all electricity consumed in the US o Average household dedicates 5 to 10 percent of is energy budget to lighting o Commercial establishments consume 20 to 30 percent of their total energy just for lighting o 50 percent or more of the energy is wasted by obsolete equipment, inadequate maintenance, or inefficient use o Echnologies developed during the past 15 years can help us cut lighting coss 30 percent to 60 percent while enhancing lighting quality and reducing environmental impacts Watts: unit of power i.e. the rate at which energy is consumed from he electricity supplier o Lumen: most common measure of light output (or luminous flux) Every bulb has 3 parameters listed on the package: o Lamp lumen output or ligh output o Power consumption in Watts o Life of the bulb in hours Footcandle: the standard unit of measure for illumination on a surface o A lumen of light distributed over a 1-square-foot (.09-square-meter) area o Average footcandle level on a square surface is equal to the amoun of lumens striking he surface, divided by the area of the surface o FC= lumens of light/area in square feet Example 1 A 40 Watt bulb produces about 505 Lumens and has a life of about 1,000 hours. When this bulb is used to light a room of 10 x 10 feet, these 505 lumens are distributed over 100 square feet of floor area. What is the illumination? o 505 lumens of light/100 ft 2 = 5.05 lumens per ft 2 or 5.05 fc 1 Foot candle= 1 lumen/ft2= 1 Lux (metric) How much light is needed in a room depends on the task being preformed (contrast, requirements, space, size, etc) o Light requirement also depends on the ages of the occupants and the importance of speed and accuracy of the task Ambient Lighting: general purpose lighting; an example is the lighting used in hallways for safety and security. An illumination of 30-50 fc is generally the max that one needs for this purpose Task lighting: lighting that is designed for specific task; reading and writing are the most light-intensive tasks and require about 50 fc at home; tasks like cooking, sewing, or repairing a wrist watch require more, about 200-300 fc. However, the area with this level of illumination will be small. Increasing the light everywhere is not required and is a waste of energy. Accen lighting: the lighting that is provided to highlight certain objects or areas; ex. Flood lighs to highlights a painting or a statue; accent lighting also illuminates walls so hey blend more closely with naturally bright areas like ceilings and windows; accent lighting can be high intensity or subtle....
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- Spring '07