How do you ventilate an attic, depending on your roof type?
Gable roof with soffits
The classic setup: continuous or evenly spaced soffit vents for intake, a ridge vent for exhaust, and gable vents closed off. Size it to 1/300 of the attic floor with balanced intake and exhaust.
Hip roof
Short ridges limit ridge vent length. Options include a ridge vent supplemented by hip vents, or box vents placed high on the rear and side slopes, all with soffit intake around the perimeter. Use one exhaust approach.
Little or no overhang
Without soffits, intake can come from vents installed along the roof edge under the first shingle courses, paired with a ridge vent. This is most easily added during a reroof.
Older homes with gable vents only
Gable vents can serve as the whole system if they meet the 1/150 area requirement, but they leave the eaves stagnant. Adding soffit intake and a ridge vent, then closing the gable vents, usually performs better.
Bonus rooms and cathedral ceilings
Sloped ceilings need a continuous air channel above the insulation from soffit to ridge in every rafter bay, or an unvented design with foam against the deck.
Sealed attic
When spray foam is applied directly to the underside of the roof deck and the attic is part of the conditioned space, the vents are closed. This approach works well when HVAC equipment sits in the attic, which is common in Georgia.
In every case
- Exhaust fans vent outdoors.
- The ceiling is air sealed.
- Insulation stays out of the eaves.