What is the purpose of a ridge vent?

Summer purpose

Sun on the roof heats the attic air, which rises to the peak. The ridge vent gives that air an exit so it does not build up and radiate down into insulation, ducts and ceilings. In Georgia, where ducts often run through the attic, that matters for comfort as well as the roof.

Winter purpose

Moist air from the house finds its way into the attic. The ridge vent lets it leave before it condenses on the cold deck, which prevents frost, dripping and mold.

Year round purpose

• Protecting the deck from repeated wetting and drying.
• Meeting the ventilation conditions in shingle warranties.
• Providing exhaust without the extra holes of individual vents.

Why at the ridge specifically

It is the highest point, so the stack effect pulls hardest there; it is where wind creates the most suction; and water sheds away from it in both directions. Exhaust placed lower on the slope can act partly as intake and is more exposed to runoff.

What a ridge vent cannot do

It cannot cool your living space much on its own, make up for missing insulation or overcome blocked intake. Read attic heat and shingles and roof ventilation basics.