Why Your Gable Vents and Ridge Vent Are FIGHTING Each Other · Crawl Space Ninja Show · Radar

Understanding Attic Ventilation0:28 – 2:21

Michael ChurchHost

0:28

The best driving force in your attic is the stack effect.

Michael ChurchHost

0:31

Warm air rises, it's less dense, so it wants to exit high and pull cool air from below.

Michael ChurchHost

0:38

In most modern homes, your attic works just like a chimney.

Michael ChurchHost

0:42

Cool air in the bottom, warm air out the top, no electricity required.

Michael ChurchHost

0:47

Gable vents don't benefit from the stack effect nearly as well because they're not located at the highest point in the attic.

Michael ChurchHost

0:54

They're on the sides.

Michael ChurchHost

0:56

So what actually moves air through a gable vent most of the time is wind.

Michael ChurchHost

1:00

And I don't know about you, but I don't want my attic depending on whether it's breezy outside.

Michael ChurchHost

1:05

I've measured attics at over 140 degrees on a dead calm afternoon where the gable vents were wide open and doing absolutely nothing.

Michael ChurchHost

1:14

Now, here's the part that most homeowners have never had explained to them.

Michael ChurchHost

1:18

If your attic has gable vents and a ridge vent, they can actually fight against each other.

Michael ChurchHost

1:23

Think of it like putting two straws in the same drink.

Michael ChurchHost

1:26

One of them is stealing from the other.

Michael ChurchHost

1:28

Wind blowing a certain direction, especially straight across the ridge line, can pull air backward through part of your system.

Michael ChurchHost

1:36

Air that's supposed to be leaving through the ridge vent gets pulled in through a gable vent instead, shoots straight across, and exits out the other side without ever touching the corners of your attic.

Michael ChurchHost

1:47

Building scientists call this short-circuiting.

Michael ChurchHost

1:50

I just call it wasted ventilation.

Michael ChurchHost

1:52

I remember crawling into an attic where the homeowner just couldn't understand why his ridge vent wasn't helping at all.

Michael ChurchHost

1:58

About 10 seconds after I got up there, I found the problem.

Michael ChurchHost

2:01

Every soffit vent was buried under blown-in insulation.

Michael ChurchHost

2:04

No baffles were installed, so the insulation had slid right down and choked off the intake completely.

Michael ChurchHost

2:11

That ridge vent had nothing to pull from down low, so it was pulling air sideways from the gable vent instead and short-circuiting the whole system before it ever had a chance to get started.

Understanding Attic Ventilation0:28 – 2:21

Michael ChurchHost

0:28

The best driving force in your attic is the stack effect.

Michael ChurchHost

0:31

Warm air rises, it's less dense, so it wants to exit high and pull cool air from below.

Michael ChurchHost

0:38

In most modern homes, your attic works just like a chimney.

Michael ChurchHost

0:42

Cool air in the bottom, warm air out the top, no electricity required.

Michael ChurchHost

0:47

Gable vents don't benefit from the stack effect nearly as well because they're not located at the highest point in the attic.

Michael ChurchHost

0:54

They're on the sides.

Michael ChurchHost

0:56

So what actually moves air through a gable vent most of the time is wind.

Michael ChurchHost

1:00

And I don't know about you, but I don't want my attic depending on whether it's breezy outside.

Michael ChurchHost

1:05

I've measured attics at over 140 degrees on a dead calm afternoon where the gable vents were wide open and doing absolutely nothing.

Michael ChurchHost

1:14

Now, here's the part that most homeowners have never had explained to them.

Michael ChurchHost

1:18

If your attic has gable vents and a ridge vent, they can actually fight against each other.

Michael ChurchHost

1:23

Think of it like putting two straws in the same drink.

Michael ChurchHost

1:26

One of them is stealing from the other.

Michael ChurchHost

1:28

Wind blowing a certain direction, especially straight across the ridge line, can pull air backward through part of your system.

Michael ChurchHost

1:36

Air that's supposed to be leaving through the ridge vent gets pulled in through a gable vent instead, shoots straight across, and exits out the other side without ever touching the corners of your attic.

Michael ChurchHost

1:47

Building scientists call this short-circuiting.

Michael ChurchHost

1:50

I just call it wasted ventilation.

Michael ChurchHost

1:52

I remember crawling into an attic where the homeowner just couldn't understand why his ridge vent wasn't helping at all.

Michael ChurchHost

1:58

About 10 seconds after I got up there, I found the problem.

Michael ChurchHost

2:01

Every soffit vent was buried under blown-in insulation.

Michael ChurchHost

2:04

No baffles were installed, so the insulation had slid right down and choked off the intake completely.

Michael ChurchHost

2:11

That ridge vent had nothing to pull from down low, so it was pulling air sideways from the gable vent instead and short-circuiting the whole system before it ever had a chance to get started.