Attic Ventilation, Balanced Soffit & Ridge Vent NFA Calculator
Calculate Net Free Vent Area (NFA in sq inches & cm²), balanced 50/50 intake soffits and exhaust ridge vent lengths per the 1:150 or 1:300 building code rule.
Total Required Net Free Vent Area (NFA cm²)
Calculator Inputs
Total Required Net Free Vent Area (NFA cm²)
Continuous Ridge Vent Length (Linear Meters)
Individual Soffit Intake Vent Grilles
Total NFA in Square Inches
50% Eaves Intake NFA
50% Ridge Exhaust NFA
50/50 Balanced Intake vs. Exhaust Ventilation Breakdown
Balanced passive ventilation requires 50% continuous intake at lowest eaves and 50% exhaust at highest roof ridge.
All engineering calculations, structural estimates, and electrical sizing metrics are provided for preliminary estimation only. Always ensure compliance with relevant statutory building codes and occupational safety standards, verified by a certified professional engineer before practical implementation.
Calculation Methodology
Total NFA = Attic Floor Area / Code Ratio (150 or 300). Intake NFA = Total NFA * 0.50. Exhaust NFA = Total NFA * 0.50. Ridge Vent Length = Exhaust NFA / Net Rating per Meter.
Frequently Asked Questions
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