What Is The Difference Between Active & Passive Ventilation? - Solar Attic Fans

Episode 28

"Active air flow is actually where it's controlled where it come on, say 85 degrees is where the fans come on and it's gonna start actively pulling the air through your soft events and then pulling the heat out of the attic space and reducing the attic temperature."

- Tom, The Attic Fanatic

 

On this episode of The Austin Solar Attic Fans Podcast, Check A Pro Joe talks with Tom The Attic Fanatic about the difference between active and passive ventilation and how the solar attic helps with active ventilation.

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Episode Transcript

(00:00):
On the check.
A pro radio show,
I get this question a lot.
It's about how to control the temperature in the home,
how to be comfortable.
And here in Texas it's really hot,
especially in the summertime.
So most of us if our house was built,
well,
it has ventilation.
I've asked Tom,
the attic fanatic from Austin solar attic fans to join me to ask me the que to answer the question.

(00:24):
What's the difference between passive and active ventilation?
Hey,
Tom.
Hey,
so the difference between passive and active.
So passive airflow is basically kind of think of it like a sailboat on a lake.
You need airflow to make that boat move versus like active would be like a power boat.
You got an engine and a propeller and we push it through the water.

(00:45):
So that's the difference.
So when we have passive would be like a static vents,
ridge vents up on the top of the roof.
Basically,
it's just letting the heat kind of escape,
but it's not actually drawing the heat out.
Active air flow is actually where it's controlled where it come on,
say 85 degrees is where the fans come on and it's gonna start actively pulling the air through your soft events and then pulling the heat out of the attic space and reducing the attic temperature.

(01:09):
So that's the,
the difference.
The calculations that we do is if you have an attic that say,
uh under 15 ft tall,
like,
so it's like a chimney effect.
The taller the attic,
the more passive airflow will start to work.
The lower the,
the attic height,
the harder it is for that air to escape,
it doesn't create like a natural draw.
So there's a lot of things,

(01:30):
I'll just go real quick.
Couple of things that we look at when we look at a house,
how high is the attic from the attic floor to the top of the roof that's gonna create the natural draw for passive airflow.
Active airflow doesn't matter if it's only 2 ft tall.
That's the beauty of active airflow.
It always works.
It's like a powerboat.
It always goes fast.
A sailboat,
it could go fast if we got enough wind.
But if there's no wind,
we're not going anywhere.

(01:50):
Same thing with an attic.
The other thing that we're gonna look at is the,
so we get the height of the attic.
But we're also gonna look is if it is a ridge vent,
is it slotted properly,
is there big enough openings basically to let the heat out of the attic space?
So that's the second thing we look at So we have to look at these different things.
And if we have a ridge vent,
how many feet of ridge vent do we have?

(02:11):
So we need a rule of thumb.
We need 3 ft of ridge vent for every 100 square feet of attic space.
So if we have 1000 square foot attic,
we need 30 ft of running ridge,
2000 square foot home,
a decent size home.
We need 60 ft,
33,000 square feet home.
We need 90 ft of running ridge in.
So what we find is most houses fail in one of these categories,

(02:32):
not enough attic height,
not enough ridge vent on length.
So we may have the height,
but we don't have the length.
We may have the length and the height,
but then maybe the ridge isn't slotted properly.
So in almost every case,
there is a an issue where we can make an argument.
You know what if we add some active airflow,
think of it as a turbocharger for your attic,
it's gonna increase the air volume and lower those attic temperatures.

(02:54):
And that's what's gonna make your house more comfortable and more efficient.
Once again,
Tom,
the attic fanatic from Austin solar attic fans saves the day.
It's very simple.
All of Tom's information is located in the show notes and the real key here because I have one of these on my home that Tom installed himself.

(03:14):
Yeah.
Well,
the real key here is to get a solar attic fan and to get the correct size and we'll talk about that on another program.
Tom.
Thank you so much for joining me today.
Thanks for having me.
I appreciate it.