How do I install proVent? 1. Slide proVent over top plate. proVent PV2248 Use for 24” on-center joist spacing 2. Secure proVent to roof deck with staples on outer flanges. 3. proVent PV1448 Use for 16” on-center joist spacing How many vents will I need? One proVent ventilation channel per rafter or truss cavity is recommended. Without ventilation channels air cannot flow freely from the soffit to the exhaust vents. Poor air flow reduces insulation efficiencies and accelerates problems due to moisture.