Balanced Attic Ventilation: Intake Comes First
Bulletin revision: February 1, 2021
A vented attic needs an effective intake-to-exhaust path. GAF warns against insufficient intake and mixing systems that can reverse airflow
GAF technical bulletin: Proper attic ventilation.
What this means for your roof
A vented attic needs an effective intake-to-exhaust path. GAF warns against insufficient intake and mixing systems that can reverse airflow. Vent sizing must account for usable net free area and the applicable design requirements.
A useful question for your contractor
Ask for intake and exhaust calculations, not just a count of roof vents.
Ask for the answer to be tied to the actual roof condition and the exact product being installed. Keep the agreed repair or installation detail with your estimate and project photos.
Bulletin revision: February 1, 2021. This is the date of the manufacturer source, not a claim that this website guide existed on that date.
Read GAF: Proper attic ventilation
This homeowner summary explains the cited bulletin. The complete manufacturer document and current product instructions govern the installation details. A requirement for one manufacturer or product should not be transferred to another without checking.