The 18 inch Aura Gravity Ventilator is 18 inches in diameter and has a 12 inch tall collar. The model number is AV-18-C12 and has 254 inches of Net Free Area (NFA). All 18 inch gravity ventilators come with a standard 24″ x 24″ square flange flashing.
Exhaust vents with a collar height of 12 inches are for low slope or flat roof ventilation. However, if installed less than 4 feet from the peak, this roof vent can go on a 0/12 to 5/12 pitch roof in all climate zones. See the installation guides for help installing.
18 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 Ventilators rely on the Venturi Effect which occurs when the wind blows against the outer louvers. It creates a spinning upward draft through the vent allowing air to dynamically flow out of the vent. Even the smallest breeze can create exhaust ventilation to draw out air from the vent.
The Aura Gravity Roof Vents are made of durable rust-free aluminum. The vent head has a flat one-piece spun lid that prevents rain and snow from entering the vent. The round aerodynamic design can withstand harsh weather and wind forces beyond 200 mph. Therefore, wind speeds of 11 mph for an 18 inch Gravity Ventilator produces 634 CFM of air exhaust for attic ventilation.
The inner louvers of the roof vent prevent insects and animals from entering the attic. The louvers also allow the air to flow freely to the outside.
AVP’s Aura Gravity 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.