Coefficient of Utilization (CU)
The coefficient of utilization is the percent of the lumens from the lamp that finally find their way to the work plane. This number depends on the particular fixture type, the number of lamps in it, the lens used, its beam pattern, the shape of the room (Room Cavity Ratio, RCR) and the reflectances of the ceiling (Rc), walls (Rw) and floor (Rf). Generally a Dirt Depreciation Factor and other Light Loss Factors are used to multiply CU.

Use for Estimating Purposes Only.

• The numbers are taken from generic fixture data from the IES handbook for an RCR = 1 and from representative data from fixture manufacturers.
• Contact fixture manufacturer for correct values.

	High Bay Spun Aluminum CU ~ 0.80		Fluorescent Industrial CU ~ 0.85
	High Bay Acrylic CU ~ 0.75		T5 or T8 Industrial with Lens CU ~ 0.75
	High Bay Acrylic CU ~ 0.85		T5 or T8 Industrial Open CU ~ 0.88
	Low Bay Lensed CU ~ 0.70
	Low Bay Acrylic CU ~ 0.75

	Acrylic Lensed Troffer CU ~ 0.81		Basic Fluorescent Strip CU ~ 0.84
	Deep-Cell Parabolic Louver CU ~ 0.72		Indirect Lighting Rc = 80% use CU ~ 0.59 Rc = 50% use CU ~ 0.37
	Small-Cell Parabolic Louver CU ~ 0.55		Incandescent / CFL Downlight CU ~ 0.71
	Small-Cell Plastic Grid 1/2" CU ~ 0.78