Floor Cavity Ratio

The lumen method in brief consists of calculation of the cavity ratios of the upper middle and lower volumes of the space to be lighted.

Floor cavity ratio.

Room surface reflectances can be predicted in a new design or measured in an existing facility. Floor cavity ratio us number representative of the geometry of the part of a room between the floor and the utilization plane used in calculation of utilization factor or utilance. The cu is computed based on the space reflectance properties ceiling wall and floor as well as the space s room cavity ratio rcr. Room surface reflectance reflected reading incident reading.

Effective floor cavity reflectance 20 per pfc 0 20 ceiling pcc 80 70 50 wall pw 70 50 30 70 50 30 50 30 rcr zonal cavity method effective floor reflectance 20 room cavity ratio 0 118 118 118 115 115 115 109 109 1 109 104 100 106 102 98 97 94 2 99 91 85 96 89 83 85 80 3 91 81 73 88 79 72 75 69 4 83 72 63 81 70 62 67 60. Hcc distance in feet from luminaire to ceiling hrc distance in feet from luminaire to work plane hfc distance in feet from work plane to floor l length of room in feet w width of room in feet an alternate formula for calculating any cavity ratio is. If the entire room is considered as a cavity the room height becomes height cavity and cr 10 k r. Post navigation 9 4 5 2 1 a number computed by using the distance from the floor to the work plane h f as height cavity in the equations given in cavity ratio cr.

Floor cavity ratio 5 x floor cavity depth x room length x room width room length x room width. Room cavity ratio room cavity ratio aka rcr is the volume between the fixture and height of calculation workplane height is typically 30 inches above the floor a rooms rcr will always be between 1 and 10 5xmhx l w room area rcr room cavity ratio the rcr can vary depending on the height of the fixture as shown here with wall. The relationship between cavity ratio and room coefficient k r should be noted. Floor cavity ratio fcr.

Cr frac 2 5 left height cavity right left perimeter cavity right area of cavity base note. The lower cavity is from the floor to the working height the upper cavity is from the lower edge of the luminaires to the ceiling and the middle cavity is the volume between these planes. Floor cavity ratio 2 5 x 385 fcr 96 symbol value table ro en room wid w 26 5 ceiling ca hcc 25 room cavity height feet hrc 5 25 floor cavi hfc 2 5 lamp lum n depreciation lld 85 b maintenan om l gth feet l 25 5. The rcr is calculated based on the room cavity height rch and the lighting calculation workplane which is a property of each space instance.

Note the floor cavity ratio is given by the formula. Floor cavity ratio fcr 5 hfc l w l x w where.