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NFA Balancing & Venting Machine

Professional NFA calculation tool for balancing intake and exhaust. Ensure 50/50 airflow to prevent code failure and shingle blistering. No sign up required. Free to use.

Frequently Asked Questions

Everything you need to know about this roof ventilation calculator tool.

Why should I strictly enforce a 50/50 NFA balance between intake and exhaust?
Balanced ventilation prevents 'Negative Pressure.' If exhaust exceeds intake, the system will pull conditioned air from the house or moisture from the crawlspace into the attic, leading to mold growth and potentially voiding the shingle manufacturer's warranty.
How do I calculate NFA for 'Soffit-to-Ridge' systems?
Calculate total ridge length and attic floor area. Use this tool to find the required NFA, then ensure your soffit intake exceeds or matches the ridge exhaust. A 1:150 ratio is the standard IRC requirement for roofs without a dedicated vapor barrier.
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