Vented vs. solid soffit — how intake net free area is counted
Intake is counted from the perforated area, not the panel length — a solid soffit adds none. Aim for intake ≥ 50% of the roof’s total net free vent area (IRC R806.2).
What this diagram shows
Three soffit panels seen from below. A solid panel has no perforations and provides zero intake net free area, so it needs separate vents. A center-vented panel has a perforated strip down the middle and gives about 5 to 9 square inches of net free area per linear foot. A fully perforated panel gives about 9 to 14. Net free area is counted from the open, perforated area, not the length of the panel, and code wants intake at the soffit to be at least half of the roof’s total vent area.
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Soffit & Fascia Calculator
Free soffit and fascia calculator — soffit panels, fascia boards, and F- and J-channel from your eave run and overhang depth, with vented-intake guidance.
