Ventilation serves the dual purpose of preventing moisture build-up in the attic during cold months and preventing heat build-up during warm weather. According to Ace Hardware, an effective attic ventilation system should have both intake and exhaust vents. Intake vents usually are near the bottom of the attic while exhaust vents are near the top. The main types of roof vents are soffit intake vents, gable intake vents, ridge vents, turbine vents, and fan-driven vents.
Soffit Intake Vents
Soffit vents install along the soffit, which is the panel under the eaves of the house between the wall and the fascia board. Continuous soffit vents consist of a long slot cut into the soffit and covered with a louvered panel and screen. Circular and rectangular soffit vents are holes cut into the soffit and covered with screens and louvered panels.
On buildings with little soffit area, you may use a vented drip edge for intake ventilation. It essentially extends the drip edge of the roof a few inches providing space for a vent between the outside of the fascia board and the drip edge.
Gable Intake Vents
Gable vents are not as effective as soffit vents because the air circulation only occurs near the gable. They are triangular openings in the gable wall at the roof peak, usually covered with screens and louvres.
According to Ace Hardware, builders consider ridge vents the most effective exhaust vent they use. The opening is a slot cut along the length of the roof ridge providing complete and continuous ventilation to the attic. A shingled metal or plastic cover goes on the opening. Although it is just as effective, a metal ridge vent may detract from a home's curb appeal. On the other hand, the shingle-over ridge vent can be almost invisible.
Turbine vents are effective, but high profile. They are openings in the upper third of the roof covered with metal flashing and a round, free-spinning, slotted metal top. Although the airflow through the vent may increase when the wind turns the turbine, they are effective vents without it.
Fan-driven vents use electricity to power a thermostat-controlled fan. The electricity sometimes comes from solar cells, but usually from the power grid. They are effective ventilators but have a shorter lifespan than the passive vents.
Other Vent Types
Steeply pitched roofs may use a vent shaped like a dormer, called a tombstone vent. So-called low profile vents are low-cost and have metal covers of various shapes.