9.19.1.2.Vent Requirements

(1) Except as provided in Sentence (2), the unobstructed vent area shall be not less than 1/300 of the insulated ceiling area. (2) Where the roof slope is less than 1 in 6 or in roofs that are constructed with roof joists, the unobstructed vent area shall be not less than 1/150 of the insulated ceiling area. (3) Required vents may be roof type, eave type, gable-end type or any combination thereof, and shall be distributed (a) uniformly on opposite sides of the building, (b) with not less than 25% of the required openings located at the top of the space, and (c) with not less than 25% of the required openings located at the bottom of the space. (4) Except where each roof joist space referred to in Sentence (2) is separately vented, roof joist spaces shall be interconnected by installing purlins not less than 38 mm by 38 mm on the top of the roof joists. (5) Vents shall comply with CAN3-A93-M, “Natural Airflow Ventilators for Buildings.”