Attic Ventilation Calculator

Tips For Assessing Your Needs

Proper attic ventilation consists of a balance between air intake (at your eaves, soffits or fascias) and air exhaust (at or near your roof ridge).

The U.S. Federal Housing authority recommends a minimum of at least 1 square foot of attic ventilation (evenly split between intake and exhaust) for every 300 square feet of attic floor space.

Always have a balanced ventilation system. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation.

How to Calculate

1. Measure
Enter the length and width or the total square footage of the attic floor.
2. Calculate
Enter the length and width or the total square footage of the attic floor.
3. Identify
See quantities below for each GAF Ventilation Product (typically rounded up).
Use this calculator to help determining the proper amount of attic ventilation based on U.S. FHA 1/300 guidelines.*
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Suggestions for ft x ft Area

Suggestions for sq. ft. Area

Numbers shown represent the recommended total number of units required for a single product.
384 Minimum Sq. In. of Net Free Area of exhaust needed at or near the ridge.
384 Minimum Sq. In. of Net Free Area of exhaust needed at or near the ridge.

Helpful Hint

For the 1/150 attic ventilation requirement, simply double the amount of exhaust and intake calculated.
Note: N/R = not recommended

Exhaust Ventilation

cobra® & truslate® plastic vents
Cobra® Exhaust Vent - Mesh Rolls (Lineal Feet)
Master Flow® Aluminum Ridge Vent (Lineal Feet)
Master Flow® Roof Louvers (# of Vents)
Master Flow® Wind Turbines (# of Vents)

Intake Ventilation

Cobra® Intake Vents (Lineal Feet)
Master Flow® Soffit/Undereave Vents (# of Vents, except for LSV8)
Master Flow® Solar-Powered Intake Vent (# of Vents)

Intake or Exhaust Ventilation

Note: Gable louvers are typically installed in pairs
Master Flow® Metal Gable Louvers (# of Vents)
MasterFlow® Plastic Gable Louvers (# of Vents)
MasterFlow® Plastic Circular Louvers (# of Vents)

Exhaust Ventilation

Master Flow® Power Attic Vents - Roof Mount (# of Vents)
Master Flow® Power Attic Vents - Gable Mount (# of Vents)
Master Flow® Green Machine Solar Vents (# of Vents)

Intake Ventilation

Cobra® IntakePro (Lineal Feet)
Cobra® Fascia Vent (Mesh Roll) 1" (Lineal Feet)
Cobra® Fascia Vent (Mesh Roll) 1.5" (Lineal Feet)
LSV8 Metal Continuous Soffit Vents (Lineal Feet)
EAP 4x12 Plastic Soffit Vents (# Of Vents)
EAC 16x4 Metal Soffit Vents (# Of Vents)
EAC 16x8 Metal Soffit Vents (# Of Vents)
EmberShield® Closeable Soffit Vents (# Of Vents)
*Note: The 1/300 rule is a general rule and does not apply to all situations. Local building codes, when stricter, take precedence. Always consult a design professional for cathedral ceilings, insulated roof decks, etc.