CSLB General Building (B)Finishes and Building EnvelopeMedium
A contractor is sizing attic ventilation for a home and providing both ridge (exhaust) and soffit (intake) vents. Per standard ventilation balance practice, how should the net free ventilation area typically be distributed between intake and exhaust vents?
- A50% intake, 50% exhaust
- B25% intake, 75% exhaust
- C100% intake, 0% exhaust
- D75% intake, 25% exhaust
Show answer & explanationAnswer & explanation
Correct answer: A. 50% intake, 50% exhaust
Balanced attic ventilation systems typically split the required net free ventilation area evenly, with approximately 50% of the total provided as intake (soffit) vents near the eaves and 50% as exhaust (ridge) vents near the top of the roof. This balance promotes proper airflow from low to high points in the attic, preventing moisture buildup and heat stagnation.
Why the other options are wrong
- B. Too much exhaust relative to intake can starve the system of incoming air.
- C. Without exhaust venting, hot air cannot escape at the ridge.
- D. An imbalanced split can create excess intake without enough exhaust capacity.
Attic Ventilation Balance
A balanced attic ventilation system splits the total required net free vent area evenly between intake (soffit) and exhaust (ridge) vents to promote consistent low-to-high airflow.
- Standard balance is 50% intake, 50% exhaust
- Intake vents are placed at the eaves/soffits
- Exhaust vents are placed at the ridge or upper roof
Memory trick: 'Half in, half out' — balanced attics split air flow evenly.