Mixing Two Different Exhaust Vents on Your House Is a Mistake
One of the most potentially troublesome attic ventilation mistakes is having
two different types of exhaust vents on your house—for example, mixing a
ridge vent with a powered fan, a roof louver, a gable louver or a wind turbine.
Technically, this mistake is called short-circuiting the attic ventilation system.
(See illustration on above)
Here’s what can go wrong during short-circuiting: Because air always follows the
path of least resistance and is always looking for the nearest opening, the ridge
vent at the peak of your roof could pull its source of intake air from the powered
fan, or roof louver, or gable louver or wind turbine (each of which happens to
be the closest opening) instead of from the intake vents low at the roof’s edge or
in the soffit/eaves. Exhaust vents are not designed to be intake vents. If air enters
an exhaust vent, along with it could be rain, snow, dirt and debris right into
your attic! Furthermore, the lower portion of the attic is inadequately ventilated.
Therefore, don’t mix any two types of exhaust vents on your house if it’s one
common attic. Always stick with one system.
You can download the Air Vent literature that says this