The Ontario Building Code | Mansard or Gambrel Roof
220.127.116.11. Mansard or Gambrel Roof
(1) The lower portion of a mansard or gambrel style roof need not be ventilated.
(2) The upper portion of roofs described in Sentence (1) shall be ventilated in conformance with the requirements in Articles 18.104.22.168. to 22.214.171.124.