Roof ventilation provides and regulates the air flow in a building. This can help moisture to escape and reduce the incidence of rot, mold and mildew within a building. The number and type of vents required depends on the roof type.
On roofs that come together to form a peak it is necessary to have a ridge vent and vents at the bottom of each side of the roof for proper ventilation. A shed-style roof does not have a peak so it only needs vents on either end of the roof. Vents on the ends of a roof are called eave vents.