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.*
Please enter a valid number
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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
SEE PRODUCT >

Cobra® IntakePro®
SEE PRODUCT >

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 >

*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.


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
Related Articles
Your attic needs to breathe. Poor ventilation may lead to excess heat and moisture and potential roof system degradation. The attic ventilation options that are best for your home will vary based on the style of your roof to ensure that each attic space has a balanced system for intake and exhaust. Balanced systems need to draw in fresh air and export hot, moist air.
A balanced attic ventilation system helps reduce damaging heat and moisture in attic spaces, which may help reduce the load on air conditioning systems and lower the risk of ice dam formation in the winter.
When considering replacing your roof, you'll need to calculate the amount of attic ventilation needed to help reduce excess heat and moisture in your attic. Excess heat and moisture can lead to premature roof system degradation and damaging ice dams in the winter.
Roof vents form the base of a home's attic ventilation system, helping it breathe while preventing roof system damage year-round. That's why it's important to understand how the various components work together to create a balanced, effective attic ventilation system.