--- title: What is the expected CFM airflow per linear foot of ridge vent? How much CFM per linear foot does a ridge vent generate? description: CFM for a non-motorized vent will vary as the wind speed changes. --- [Skip to content](https://help.gibraltarbuildingproducts.com/en/knowledge/what-is-the-expected-cfm-airflow-per-linear-foot-of-ridge-vent#main-content) English Show submenu for translations ![GBAD Full Color.png](https://blog.stealthbond.com/hubfs/GBAD%20Full%20Color.png) Open main navigation Close main navigation - English Show submenu for translations - Go to www.gibraltarbuildingproducts.com Go to www.gibraltarbuildingproducts.com Hello. How can we help you? - There are no suggestions because the search field is empty. 1. [Help Center](https://help.gibraltarbuildingproducts.com/en/knowledge?hsLang=en) 2. [Ventilation](https://help.gibraltarbuildingproducts.com/en/knowledge/ventilation?hsLang=en) 3. [Ridge Vent](https://help.gibraltarbuildingproducts.com/en/knowledge/ventilation?hsLang=en#ridge-vent) # What is the expected CFM airflow per linear foot of ridge vent? How much CFM per linear foot does a ridge vent generate? ## CFM for a non-motorized vent will vary as the wind speed changes. The airflow and velocity is directly related to pressure. Pressure can be affected by a number of variables, but mainly by wind speed (creating low  or negative pressure) over the external baffle on the ridge vent and attic air temperature (creating a positive or high pressure) within the attic space. Humidity will also play a role as the higher the humidity the less dense the attic air and thus reducing the internal air pressure and thus the pressure differential between the ridge vent and the attic. In a University of Illinois test using 4-foot sections of many brands/styles of ridge vents Air Vent's ShingleVent II ridge vent produced 75 CFM per four-foot section at 15 MPH winds. 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