Attic Fan Intake Air

According to the national roofing contractors association nrca a power vent with an airflow rate of 1 0 cubic foot per minute per square foot of attic space measured at the attic floor is generally considered to be equivalent.

Attic fan intake air.

If two different types of exhaust vents are combined for example a ridge vent and a gable louver the primary path of air becomes the distance between the two types of exhaust vents. Intake vents located at the lowest part of the roof under the eaves allow cool air to enter the attic. Not having enough intake air could lead to negative pressure. Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge.

A minimum of 70 linear feet or 700 sq in. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. Similar to the static method adequate amounts of intake air into the attic space should be provided. That path is supposed to be from low in the attic intake vents to the highest possible exit point in the attic exhaust vents.

See figure 2.