Used for building lighting to calculate illumination levels, the Coefficient of Utilization (COU) measures the efficiency of a fixture to use the lumens from the lamp(s) therein.
Normally found in table form, it shows a decimal (percentage of lamp lumens) based on the Room Cavity Ratio (RCR) (or zonal cavity, often the same number) on the Y axis and the ceiling and wall reflectances on the X axis. Normally the floor reflectance is assumed to be 20%, and is only stated as a note below the chart.
Williams Downlighting's catalog page has specification sheets showing their COU's and how they relate to the RCR and room reflectances.
Normally found in table form, it shows a decimal (percentage of lamp lumens) based on the Room Cavity Ratio (RCR) (or zonal cavity, often the same number) on the Y axis and the ceiling and wall reflectances on the X axis. Normally the floor reflectance is assumed to be 20%, and is only stated as a note below the chart.
Williams Downlighting's catalog page has specification sheets showing their COU's and how they relate to the RCR and room reflectances.