vents for metal roof in a house

[sunyaer]

This is from Ontario building code
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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.

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From my observation on houses with metal roof in the city of Toronto, except vents on the roofs for plumbing purpose, it doesn't seem that there are other vents on the roofs as per the requirements of 9.19.1.1. (1) and (2), is there anywhere in the code that vents for metal roof can be exempted from these requirements?

 

[ICE]

Eave and gable vents can serve the purpose.

 

[Msradell]

Eave and gable vents can serve the purpose.

Definitely gable vents can count but I'm not so sure about eave vents, since they are a low point, I thought they were only counted for intake air area.

 

[ICE]

The ideal configuration is high and low openings (vents). As warm air rises, cooler air is pulled in the lower vent (opening).

R806.2 Minimum vent area. The minimum net free ventilating area shall be 1/150 of the area of the vented space.
Exception: The minimum net free ventilation area shall be 1/300 of the vented space provided both of the following conditions are met:
1. In Climate Zones 14 and 16, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.
2. Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet below the ridge or highest point of the space, measured vertically. The balance of the required ventilation provided shall be located in the bottom one-third of the attic space. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet below the ridge or highest point of the space shall be permitted.

 

[mtlogcabin]

We see a lot of ridge vents in our area shingles or metal roofs.

Here is a cheap installation example