| 9.19.1. |
Venting |
| 9.19.1.1. |
Required Venting
- 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 transfer of moisture from the space to the exterior. (See Note A-9.19.1.1.(1).)
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| 9.19.1.2. |
Vent Requirements
- Except as provided in Sentence (2), the unobstructed vent area shall be not less than 1/300 of the insulated ceiling area.
- 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.
- Required vents may be roof type, eave type, gable-end type or any combination thereof, and shall be distributed
- uniformly on opposite sides of the building,
- with not less than 25% of the required openings located at the top of the space, and
- with not less than 25% of the required openings located at the bottom of the space.
- Except where each joist space 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.
- Vents shall comply with CAN3-A93-M, "Natural Airflow Ventilators for Buildings."
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| 9.19.1.3. |
Clearances
- Except as provided in Sentence (2), not less than 63 mm of space shall be provided between the top of the insulation and the underside of the roof sheathing.
- At the junction of sloped roofs and exterior walls, where preformed baffles are used to contain the insulation, the baffles shall
- provide an unobstructed air space, between the insulation and the underside of the roof sheathing, that is
- not less than 25 mm in dimension, and
- of sufficient cross area to meet the attic or roof space venting requirements of Article 9.19.1.2., and
- extend vertically not less than 50 mm above the top of the insulation.
- Ceiling insulation shall be installed in a manner that will not restrict the free flow of air through roof vents or through any portion of the attic or roof space.
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| 9.19.1.4. |
Mansard or Gambrel Roof
- The lower portion of a mansard or gambrel style roof need not be ventilated.
- The upper portion of roofs described in Sentence (1) shall be ventilated in conformance with Articles 9.19.1.1. to 9.19.1.3.
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