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Room Cavity Ratio

The room geometry is accounted for in cavity ratios or CR.
The equation for Cavity Ratio is:

CR = 5 x H x (L + W)
(L x W)

CR equals 5 times Height x the sum of length plus width divided by the result of length times width.

Cavity ratios can be calculated for the ceiling, room and floor by using the appropriate cavity dimensions.

Let's calculate the CR for a room with the dimensions of Height=6, Length=12, and Width=10.

12x10 equals120. So CR = 5x6x120 or 660 divided by 120. The result is a Cavity Ratio of 5.5.

For a given space, calculate the CR and then use the fixture manufacturer's CU table to select the appropriate CU.

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