Powered Gable Fans, Why They Almost Never Work

Now let's talk powered gable fans, because I bet a lot of you watching this have that exact setup.

One fan blowing in, one fan blowing out.

Here's what actually goes wrong with these.

Those motors usually burn up from running constantly trying to fight the wrong pressure.

Plus, birds build nests right in the housing and block airflow completely.

The screens get clogged with dirt and debris until they're barely breathing.

Louvers get stuck shut from age or paint or rust.

And when you got two fans, one on each gable end, they can literally overpower each other.

One pulling air while the other is trying to push air out the same space.

And neither usually wins.

Now some of you are probably thinking, I only have one powered gable fan.

It blows air out and the other gable vent allows fresh air to come in.

What's wrong with that? The problem is that the fan is going to pull air from wherever it's easier to get it from.

If your attic has soffit vents and a ridge vent, you've now created competing airflow paths.

Instead of drawing cooler outside air evenly through the soffits and up the underside of the roof deck, the fan may be pulling a lot of its replacement air straight across the attic from the opposite gable vent or from the nearest available opening.

That means large sections of the roof deck may see very little airflow at all.

The air takes the path of least resistance, not necessarily the path that gives you the best ventilation.

The goal isn't just to move air.

is to move air where you want it to go starting at the soffits traveling up the underside of the roof deck and leaving through the highest point in the attic think about trying to cool your house by putting a box fan in one window the room right in front of the fan gets plenty of air But that doesn't mean that every room in the house is getting good circulation.

Attics work in the same way.

You don't just want air moving.

You want it moving through the entire attic, from the soffit all the way to the highest point of the roof.

That's what a balanced ventilation system is designed to do.