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Ventilation Calculator

Attic Ventilation Calculator

How to Calculate

Step 1: Measure

Measure the length and width of the attic floor space to be ventilated.

Step 2: Calculate

Enter the length and width or the total square footage of the attic floor space to be ventilated.

Step 3: Identify

See recommended quantities below for each GAF Ventilation Product (typically rounded up).

Let’s get started

Use this calculator to help determine the proper amount of attic ventilation based on U.S. FHA 1/300 guidelines.*

Enter your measurements below

Length (ft)

Width (ft)

OR

Total Square Footage (ft²)

0 sq. in.

Net Free Area (Exhaust)

At Ridge

AND

0 sq. in.

Net Free Area (Intake)

At Soffit

Please Note: Some local building codes require the 1/150 attic ventilation rule. Always consult local building code requirements.

Product	Requirement

Product	Requirement

Product	Units Required

Note: Power vents require adequate intake ventilation to function correctly. Ensure your soffit/intake ventilation meets the requirements calculated above.

Attic ventilation & vent products

To find the right attic ventilation solution for your roofing project, choose from a complete line of ridge and hip vents, electric and solar power vents, roof and gable louvers, wind turbines, intake vents, and more, all from GAF.

Cobra® Rigid Vent 3™

See product

Master Flow™ SSB960A

See product

Cobra® SnowCountry® Advanced

See product

GreenMachine™ Solar Vent

See product

Cobra® IntakePro®

See product

Master Flow™ ERV5

See product

The 1/300 balanced attic ventilation rule

Proper attic ventilation consists of a balance between air intake (at or near your soffits) and air exhaust (at or near your roof ridge). The U.S. Federal Housing authority recommends a minimum of 1 square foot of attic ventilation (evenly split between intake and exhaust) for every 300 square feet of attic floor space.

Watch video

Learn about attic vent options

Are you confused about the many attic ventilation solutions available? Watch this video for a great introduction to the art and science of choosing the right attic ventilation components for your roof.

Watch video Learn more