For years we have been working with Architects and Specifiers to ensure affordable roof ventilation that upholds building code standards. Our passive roof vents are UL Certified, and rated to withstand wind pressure in excess of 200 mph.

Use AVP’s Roof Vent Calculator to determine the number and size of exhaust vents you will need.


For balanced ventilation, an equal amount of intake vent area (“Net Free Area”) should also be installed. Our Soffit VentsRound Back VentsPop Vents, and Universal Vents make excellent intake vents.

Choose a Product Below to Begin Calculation

Enter below the Width and Length of the attic space you intend to ventilate. You may also enter the size of the attic directly in the "Area" field at the bottom.

Enter width of space to calculate area (or enter Area below)

Enter width of space to calculate area (or enter Area below)

If you know it, you may enter the area of the attic directly here

When a vent line is selected and area entered, select the specific vent diameter to highlight the number of vents of that size which would ventilate the specified area with both 1/300 and 1/150 rule.

No Vent Line Yet Chosen - Select Above

The roof vent calculation values shown above are for the exhaust portion of the roof. The same amount of net free air inches is needed for air intake as well. Proper roof ventilation consists of 50% air exhaust and 50% air intake.

Example Building

1,000 Divided by 300 = 3.33 Total Square Feet. 50% Intake 1.7 Sq. Ft. & 50% Exhaust 1.7 Sq. Ft.

1,000 Divided by 150 = 6.66 Total Square Feet 50% Intake 3.3 Sq. Ft. & 50% Exhaust 3.3 Sq. Ft.

Building as illustration of Attic Area in Ventilation Calculator

You do not need to go back to school to understand the building science behind roof ventilation
“The basic breakdown”

Home owners and professionals alike have questions and concerns about how to properly ventilate their roof. Which roof vents are best based on roof type, climate, and budget for example:
We want to share those questions and answers with you.

Question: What are the building code requirements for ventilating a roof?

Answer: 1 square foot of ventilation for every 300 square feet of space
for pitched roofs with vapor barriers.

1 square foot of ventilation for every 150 square feet of space
no vapor barrier and for some municipalities in hot climates

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