The 8 inch Aura Gravity Ventilator is 8 inches in diameter and has a 2 inch tall collar. The model number is AV-8-C2 and has 50 inches of Net Free Area (NFA). All 8 inch gravity ventilators come with a standard 13″ x 13″ square flange flashing.
If installed on the upper portion of the roof, no more than 2 feet down from the peak, this gravity vent can go on a roof with a pitch of 3/12 to 7/12 in climate zones 1-4. For roofs that are pitched at 8/12 or greater, please notify the sales department when ordering your roof vent as the gravity vents can be modified to installed up to a 12/12 roof pitch. Email us at [email protected] or call at 1-800-ROOFVENT for any questions. If you are looking to determine the pitch of your roof, see the Roof Pitch Diagram.
The Aura Gravity Ventilator 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.
The Aura Gravity Ventilator works like a roof turbine but with no moving parts.
Aura Gravity Ventilators rely on the Venturi Effect when wind blows against the outer louvers. As a result, this creates an upward draft allowing air to freely flow in and out of the vent.
Even the smallest breeze can create exhaust ventilation so that air is drawn out of the gravity vent. This movement of air is proportional to the wind speed and is measured in cubic feet per minute (CFM). Therefore, wind speeds of 11 mph for an 8 inch Gravity Ventilator produces 185 CFM of air exhaust for attic ventilation.
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.