Determining # of Fans

Calculate the cubic area of the crawl space by multiplying the length x width x height. Divide this number by 15 to determine the minimum cfm necessary to fully ventilate the space in 15 minutes.

Example: 20' wide x 40' long x 3' high crawl space = 2,400 cubic ft.

2,400 cubic ft. / 15 (minutes) = 160 cfm necessary for four air changes per hour.

Choose two V1 or V1D ventilators or one V2D ventilator.