What are the benefits of attic ventilation?
Short answer. The main benefits of attic ventilation are a drier roof deck, longer shingle life, less moisture and mildew in the attic, and staying within the ventilation requirements of building codes and shingle warranties. Lower cooling bills are a smaller benefit than many people expect when the ceiling is well insulated.
The benefits that matter most
- Moisture control. Air leaking up from the house carries water vapor. Ventilation flushes it out before it condenses on the decking, which protects plywood and OSB from mildew, delamination, and soft spots.
- Longer shingle life. Asphalt shingles age faster when baked from both sides. Moving hot air out of the attic reduces the heat load on the underside of the roof, which matters in Georgia's long, hot summers.
- Warranty protection. Shingle manufacturers expect ventilation that meets their requirements, and inadequate ventilation can limit warranty coverage for heat related problems.
- A healthier attic. Less dampness means less mold, fewer musty smells, and less rust on nails, metal straps, and HVAC equipment.
- Ductwork in the attic. Many Georgia homes have the air handler and ducts in the attic. A cooler attic means less heat gain through the duct walls.
- Ice dam resistance. In the North Georgia mountains, a cold, ventilated roof deck helps reduce the melt and refreeze cycle that causes ice dams. It is rare in most of the state, but costly when it happens.
Benefits that get oversold
Ventilation alone will not drop your power bill dramatically. Insulation and air sealing do far more to keep attic heat out of the living space. Ventilation also cannot fix a bath fan that dumps into the attic or a roof leak; those need direct repairs.
Getting the benefits
All of these depend on balanced airflow: enough intake at the soffits, one type of exhaust up high, and insulation kept clear of the eaves. See heat, humidity, and roof life and attic heat and shingles.