Ventilation Calculator Based on VA/FHA Guidelines
This Calculator will help you to determine the proper amount of ventilation based
on the VA/FHA Guidelines. To use simply enter the dimension or square footage of
your attic and click 'Update'. The calculations are done for you. The products listed
are GAF/MasterFlow® products and the quantity numbers are rounded
up or down for your convenience.
Please note that the 1/300 or the 1/150 rule are general rules and do not apply
to all situations. Local Building Codes, when stricter, take precedence. Always
consult a design professional for cathedral ceilings, insulated decks, etc.
Using the FHA 1/300 rule
384.00 net free vent needed at
ridge
384.00 net free vent needed at
soffit
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Rigid Cobra® Vents
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Static Vents/Louvers
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Metal Soffit Vents
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ft. Cobra® RidgeRunner™
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RT 65 Static Vents
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EAC 16x4 Soffit Vents
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ft. Cobra® Rigid Vent 2™
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IR 61 Static Vents
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EAC 16x8 Soffit Vents
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ft. Cobra® Rigid Vent 3™
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R 50A Static Vents
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ft. Cobra® Snow Country™
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IR 65 Static Vents
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Plastic Soffit Vents
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ft. Cobra® Snow Country Advanced™
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SSB 960 Static Vents
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EAP 412 Series Soffit Vents
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Mesh Cobra® Vents
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Turbines/Whirley Birds
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Continuous Metal Soffit Vents
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ft. Cobra® Exhaust Vent Hand Nail
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12" Turbines
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LSV8 Series Soffit Vents
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ft. Cobra® Exhaust Vent Nail Gun
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14" Turbines
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LSV8L Series Soffit Vents
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TruSlate® Ridge Vent
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MasterFlow® Aluminum Ridge Vent
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Plastic Circular Louvers
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ft. TruSlate® Ridge Vent
(Prior to Q2 2010)
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ft. Aluminum Ridge Vent
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RLSC 2 (2") Series Soffit Vents
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ft. TruSlate® Ridge Vent
(Q2 2010 or later)
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RLSC 3 (3") Series Soffit Vents
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RLSC 4 (4") Series Soffit Vents
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MasterFlow® Power Roof Ventilators
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MasterFlow® Power SOLAR Ventilators
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PR1D 1000CFM
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PRSolar 500CFM
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Cobra® Fascia Vents
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PR2D 1250CFM
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PGSolar 500CFM
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ft. Cobra® Fascia Vent 1"
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PR3D 16000CFM
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Solar Intake Booster™
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ft. Cobra® Fascia Vent 1.5"
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ft. Cobra® FasciaFlow™
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Note: Gable vents are normally installed in pairs
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Metal Gable Louvers
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Plastic Gable Louvers
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MasterFlow® Power Gable Ventilators
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DA 12x12
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SL 8x8
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PG2 1540CFM
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DA 12x18
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SL 12x12
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PG3 1600CFM
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DA 14x24
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SL 12x18
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DA 18x24
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SL 14x24
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DA 24x30
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SL 18x24
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Using the FHA 1/150 rule
(vents placed at or near the ridge only)
1536.00 net free vent area needed
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Rigid Cobra® Vents
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Static Vents/Louvers
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TruSlate® Ridge Vents
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ft. Cobra® RidgeRunner™
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RT 65 Static Vents
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TruSlate® Ridge Vent
(Prior to Q2 2010)
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ft. Cobra® Rigid Vent 2™
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IR 61 Static Vents
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TruSlate® Ridge Vent
(Q2 2010 and Later)
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ft. Cobra® Rigid Vent 3™
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R 50A Static Vents
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ft. Cobra® Snow Country™
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IR 65 Static Vents
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MasterFlow® Aluminum Ridge Vent
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ft. Cobra® Snow Country Advanced™
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SSB 960 Static Vents
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ft. Aluminum Ridge Vent
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Mesh Cobra® Vents
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ft. Cobra® Exhaust Vent Hand Nail
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ft. Cobra® Exhaust Vent Nail Gun
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