The Round Back Static Vent is 4 inches in diameter with a 2 inch tall collar. In other words, this vent has 2 inches of clearance between the base and the inner louvers. The model RBV-4-C2 has 12 inches of net free area (NFA) and comes with a 9” x 9” square flange.
If installed no more than 18 inches from the peak on a roof pitch of 4/12 or greater, this vent can be installed in all climate zones. If installed 3 feet from the peak of the roof on a pitch of 3/12 or greater, this vent can be installed in climate zones 1-4.
The 4 inch Round Back Vent is best used for on roofs with a 3/12 to 12/12 roof pitch. The Round Back Vent comes in an array of diameters and collar heights allowing for installation in any climate zone. See the Climate Zone Chart to determine the proper collar height for installation in your area.
To determine the number of vents you may need, see our Vent Calculator.
However, if you are looking to ventilate a duct, please see our Round Back Roof Jack for vents with a tailpipe adapter. On the other hand we also have Static Vents with curb mount flanges to be installed on roof curbs.
This static vent is ideal for venting out bathroom fans or range hoods. In addition, the round design is aerodynamic to withstand wind speeds up to 200 mph. The 4 inch Round Back Vent is great for residential roof applications because of its low profile. It can also be painted to match the color of the asphalt shingles.
AVP’s Round Back Static Vents are UL Listed and rated up to 50+ PSF or wind pressure above 200 MPH. Certified by Texas Department of Insurance, Florida State Approved & Conforms to the Standards of CALFIRE.
The diameter size of all roof vents determines the Net Free Area, also known as the "NFA". NFA is the measured amount of opening each vent offers at each specific size. to be available for venting air through a specific vent size. The calculator below will find the overall number of vents needed to effectively ventilate the targeted attic space.
Once you have the area, the numbers shown below are the number of vents of that size which would ventilate the specified area with both 1/300 and 1/150 rule.
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.