Attic Ventilation: What Every Builder Should Know
How much ventilation does an attic need? The IRC requires 1 square foot of net free ventilation area to every 150 square foot of attic floor space (1/150), but does not specify the location of intake vents or exhaust vents, nor does it specify the ratio of intake to exhaust. (EXAMPLE: 2,200 square feet of attic space divided by 150 equals 14.67 square feet of required net free ventilation.) Net free ventilation is the amount of clear air space of a ventilation product after d