Roof Ventilation Calculator
Calculate the net free area (NFA) required for proper attic ventilation based on attic size, roof pitch, and vent type.
Inputs
sq ft
:12
Results
Total NFA Required
10 sq in
Vents Needed
1
Exhaust NFA5 sq in
Intake NFA5 sq in
How to Use This Calculator
- Enter attic floor area (sqft) and roof pitch.
- Set vent type (1:150 or 1:300 ratio) based on whether a vapor barrier is present.
- Enter existing intake NFA (sqin) and exhaust NFA (sqin).
- Review required total NFA, balanced intake and exhaust NFA, and vent count needed.
- Balanced ventilation (50% intake / 50% exhaust) is required -- do not add exhaust without adding intake.
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