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Podcast: Why Is Roof Ventilation So Tricky (and So Important)?

Posted August 23, 2017 by Daniel White

In this episode, Daniel talks about ventilation- or how your roof breaths. It might seem beneficial to install multiple vent styles to increase the ventilation of your roof. This can end up backfiring big time. Daniel explains why.

Podcast Transcription: RoofLifeB025-185

Shayla: You are listening to the Roof Life of Oregon podcast and I’m talking with Daniel today. Daniel, let’s talk a little bit about mixed ventilation. Is it a good thing? Is it a bad thing? Talk about that a little bit today.

Daniel: That’s a really good subject. You think, if I just keep adding vents, add as much as I can, it’s going to make the roof cooler, it’s going to make the roof healthier, just keep adding stuff to the top of the roof. It can actually work to your detriment, because it can actually short circuit the system. You don’t want to mix multiple different styles on top of the roof. They’ll work against each other.

Case and point, I went to a re-roofing client. He needs a new roof. And just recently he had a power fan installed on the roof and he loves this thing. He thinks this thing is just the cat’s meow. This thing is just going to get all that heat out of the attic and do a great job. He can hear it kick on, okay, it’s kicking on, I can hear the motor running, it’s working. The problem is, he has can vents on his roof. So those little turtle vents, you’ve probably seen them on a million roofs. Can vents that go across the very top of the roof. They let all the heat out of your attic in the summer and they let the moisture out of your attic in the winter. The problem is is when he put that power fan on, every time it turns on, it’s going to pull air  from the path of least resistance. So you’re roof is built in, let’s say, basically, an a-frame. You have a top. You have a bottom.
The cool, dry air we want to pull in comes from underneath the eave. So if you walked out the front door and looked up and looked underneath the eave, you’ll see a little vent under there. That vent is designed to pull the cool, dry air from the outside, into the attic space. It goes up into the attic, mixes with the warm, moist air and it goes out the top of the roof. That’s what the power fan is supposed to do. So if you have can vents, only can vents. If you have power fans, only power fans, because when that thing turns on, again, we want it pulling from the bottom.
The problem with this roof is, he has two can vents right next to that power fan. So when it turns on, it’s not pulling from the bottom. It’s pulling from the two can vents on the roof right next to it. So where’s the hottest part of your roof? The top. So now when it turns on, it’s sucking hot air back inside exhaust vents. So those exhaust vents have now become intake vents. They’re not designed for that. We’re sucking hot air back in the can vents and recycling. He’s probably helping the attic a little bit. He’s sucking some of the hot air out of there, but a fraction of what it could because it’s short circuiting the system. So you want to do one type of vent on the roof, and that’s it. Pick either a ridge cap, pick either power fans, or pick can vents. Only one style, that’s it, don’t mix and match.

If you’re going to have a power fan and the roof is too big, you can’t mix with other things, you may have to have two power fans. Those have to be connected to each other so that they turn on at the same time. So you don’t want one to kick on and make the other one turn into an intake. They need to be wired together. And the biggest mistake you see is homeowner’s go to a big box store, they buy a power fan, they put it in and they go, “This is great!” It’s only a thermostat. We’re a high humidity area here. You need to have not just a thermostat, but a humidistat also. In the winter, we want to get the moisture out. That’s a big one that you’ll see contractors do. They’ll only put the one type of power fan. So that’s the right thing to do with ventilation.

I’m going to put a plug in here for Air Vent, Inc. Fantastic company. We go to their training every single year. We go through it and make sure we keep ourselves updated. They’ve got fantastic videos on their website. You can go there, you’ll see Paul, you’ll love him. He talks about ventilation and the right way to do it. So go to Air Vent, Inc. Go to their website. They’ll talk about everything we just talked about.

Shayla: When it comes to ventilation, you mentioned ridge vent, can vent, power fan. Do you have a preference, or does it just depend on the environment of the home?

Daniel: We do have a preference, when possible. Every roof is different. We can’t just say, we’re going to do this on every roof. That doesn’t work. If you can, ridge vent is by far the best, if the roof will take it. You have to have enough lineal feet on the top of the roof to put that on. Some roofs, we just don’t have the room. We’ll have to go to a power fan or a hip vent, or some other kind of vent. But if you have a choice, and you’re able to, ridge vent is by far the best thing you do.

Shayla: What makes the ridge vent preferable to you guys?

Daniel: There’s no dead air spots. So it vents all the way across the entire ridge line. Can vents, there’s dead air in between, they look ugly. Ridge vent is almost invisible. So there’s no dead air. It gets the entire area. It’s less cutting on the roof, less protrusions on the roof. It’s just the best thing. The builder actually put a ridge vent on my home sixteen years ago, and it functions great. I love it.
Shayla: Touching back a little bit on the homeowner you were talking about first, what do you guys do for him? Do you replace, or remove the can vents? How does that work?

Daniel: We are still under discussions. He is still sold on those power fans. So I’m trying to convenience otherwise. His roof is perfect for a ridge vent. It is one long run. It is absolutely perfect. So we are still in discussions with him. What we would want to do is close off all those holes completely, just block them completely off, new plywood, they also make plugs designed for that. Plug them all up, cut the ridge vent whole, put a ridge vent on top. That’s what we want to do.

Shayla: So if you are interested in hearing more about what Daniel talked about today, if you have mixed ventilation in your roof now, it may be a really great idea to give Roof Life of Oregon a call to make sure that your roof is actually operating properly. If you have any more questions, reach out to the team today. Thanks, Daniel.



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