The 18 inch Aura Attic Fan with Curb Mount Flange is 18 inches in diameter and has a 12 inch tall collar. The model number is AF-18-C12-CMF and exhausts air out at 2,200 CFM. All 18 inch gravity fans come with a standard 22″ x 22″ flange to fit over roof curbs.
The Aura Gravity Fan exhausts air continuously even when the motor is off. This attic fan works passively because of the Venturi Effect. When the wind blows against the outer louvers this creates an upward draft which allows air to freely flow in and out of the vent. This Attic Fan is also available with an optional Shut-Off Switch, Thermostat and Humidistat (THSOS).
The curb mount flange allows for easy installation on roof curbs of the same diameter. In addition, the curbed flange can be used as a hatch to access the ductwork below. We recommend installation on roofs with a pitch of 2/12 or less.
With 1/2 horsepower and 2,200 CFM, this 18 inch vent is perfect for ventilating large attic spaces or plenums.
Even when the motor is off, the attic fan will still ventilate passively. In other words, even the smallest breeze can create exhaust ventilation to draw air out of the fan.
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 18 inch attic fan produces 634 CFM of air exhaust for attic ventilation.