Attic Ventilation Calculator

How to Calculate

1. Measure
Measure the length and width of the attic floor space to be ventilated.
2. Calculate
Enter the length and width or the total square footage of the attic floor space to be ventilated.
3. Identify
See recommended quantities below for each GAF Ventilation Product (typically rounded up).
Use this calculator to help determine the proper amount of attic ventilation based on U.S. FHA 1/300 guidelines.*
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Suggestions for ' x ' 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.
And
384 Minimum Sq. In. of Net Free Area of intake needed at or near the soffit.

Please Note:

Some local building codes require the 1/150 attic ventilation rule, which increases the minimum attic ventilation needed. Always consult local building code requirements in your area for details.
Note: N/R = not recommended

Exhaust Ventilation

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

Intake Ventilation

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

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)
Master Flow® Wind Turbines (# of Vents)

Intake Ventilation

Cobra IntakePro® (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)


PRODUCTS & RESOURCES
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.

 

View all products

Cobra® Rigid Vent 3™
SEE PRODUCT > 

Cobra® SnowCountry® Advanced
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Cobra® IntakePro®
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Master Flow® Roof Louver SSB960A - Aluminum Slant-Back
SEE PRODUCT > 

Master Flow® Power Attic Vent ERV5 - Roof Mount
SEE PRODUCT > 

Master Flow® GreenMachine™ High-Power Solar Roof Vent - PRSOLAR2
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. Always have a balanced ventilation system. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation.
Watch Video
*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.

Learn About Attic Vent Options

Are you confused about the many attic ventilation solutions available? Curious why one roof would get ridge ventilation and another would incorporate power vents or a roof louver? 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


Your Top Attic Ventilation Questions Answered

How to Ventilate an Attic - How Attic Ventilation Works | GAF
How to Select Products for Your Attic Ventilation System | GAF Roofing
How to Plan a Balanced Attic Ventilation System | GAF Roofing Materials
How to Avoid Common Attic Ventilation Installation Mistakes | GAF Roofing
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