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Attic Fan CFM Calculator
Attic square footage gives CFM rating for an attic fan plus net free area needed.
Fan CFM
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- Soffit NFA (sq in)
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- Air changes / hr
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- Recommended fans
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FAQ
Why ventilate the attic? +
Reduces summer heat load, prevents ice dams in winter, and extends shingle life.
NFA? +
Net Free Area, the actual open area in vents after subtracting screen mesh.