Residential · IRC 2021 §R806.1 / §R806.2
Attic Ventilation — Net Free Area
Attic ventilation: 1/150 base net free area, 1/300 exception with a vapor retarder in Zones 6-8, 40-50% in upper vents within 3 ft of the ridge, balance low.. Referenced to IRC 2021 §R806.1 / §R806.2.
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