The 30 inch Aura Gravity Ventilator is 30 inches in diameter and has an 8 inch tall collar. The model number is AV-30-C8 and has 706 inches of Net Free Area (NFA). All 30 inch gravity ventilators come with a standard 40″ x 40″ square flange flashing.
Exhaust vents with a collar height of 8 inches are typically for low slope or flat roof ventilation. However, if installed on the upper portion of the roof, this roof vent can go on a 0/12 to 5/12 pitch roof in all climate zones.
30 inch diameter roof vents are commercial size, therefore, should be in commercial settings. For those looking to ventilate their homes, please view roof vents with a smaller diameter.
The Aura Gravity Ventilator works like a roof turbine but with no moving parts.
Aura Gravity Vents rely on the Venturi Effect when the 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. Therefore, wind speeds of 11 mph for a 30 inch Gravity Ventilator produces 1,692 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.