Required Venting

(1)  Except where it can be shown to be unnecessary, where insulation is installed between a ceiling and the underside of the roof sheathing, a space shall be provided between the insulation and the sheathing, and vents shall be installed to permit the movement of air from the space to the exterior.

Article 9.19.1.1 Ontario Regulation 332/12 Building Code,   Information published by oncodes.ca for educational purposes only.