| quotient of the sum of the areas of the floor and the working plane and the sum of the area of the walls bounded by the floor and the working plane, used in the calculation of the utilization factor or utilance
Note 1 to entry: The floor cavity index is given by the formula
where a and b are the dimensions of the sides of the room and hf is the distance from the floor to the utilization plane.
Note 2 to entry: See also "ceiling cavity index" and "room index".
Note 3 to entry: The floor cavity index has unit one.