Wind Turbines are a type of attic exhaust vent that make up half of a balanced attic ventilation system for each roof. Intake vents make up the other half of the system. Together they help remove any built-up heat and moisture inside the attic for year-round ventilation. Use the Home Depot calculator to determine how many individual Wind Turbnes are needed per roof.. Patented Delrin bearings assure long-lasting, quiet operation with no metal parts to squeak. 2-piece base and fits 3/12 to 12/12 roof pitch. Large flashing allows for easy installation. Wind turbines are available in both internally and externally braced styles. 132 sq. in. of net free area airflow each. 14 in. round opening. Maintenance-free top and bottom dual bearing system. Aluminum construction. Part of a balanced attic ventilation system for year-round airflow. Helps to fight heat and moisture buildup inside an attic as well as ice dams in cold climates. Requires intake ventilation for proper performance. Use the Home Depot online calculator to determine how many are needed for each attic. <br /><br /><center><a href="https://www.dataworksinfo.com/AirVent/AirVentCalc_HomeDepot.asp" target="_blank"><br /><br /><center><img src="https://inlinecontent.thdstatic.com/22/AIR VENT INC/ventilation-calculator_Turbines_1.jpg"></center><br /></a></center><br />. <br /><br /><center><img src="https://inlinecontent.thdstatic.com/22/AIR VENT INC/1211390.jpg"></center><br />. Bracing: Externally Braced. Net-Free Area (Sq. In.): 132