Roof Ventilation Calculator
Calculate attic ventilation requirements
sq ft
Formula
NFA = Attic Area × 144 / 150 (or 300)
1:150 ratio without vapor barrier, 1:300 with vapor barrier.
Examples
1500 sqft, no vapor barrier
1440 sq in NFA needed.
Frequently Asked Questions
About Roof Ventilation
Calculate attic ventilation requirements.