Some homeowners think if they just keep adding vents, it’s going to keep the roof cooler and healthier. But if you start mixing different styles of ventilation, it can actually short circuit the system and work against you.

Case and point: I was recently working with a client who needs a new roof. He just installed a power fan on his roof and loves it. He thinks it’s the cat’s meow. He thinks it’s really working to get all the heat out of his attic.

The problem is that he also has can vents on his roof. They let all the heat of out of your attic in the summer, and the moisture out during the winter. Every time you turn on a power fan, it pulls air from the path of least resistance. In this client’s case, it’s pulling air from the two can vents right next to it.

What’s the hottest part of the roof? The very top. So every time his power fan turns on, it’s sucking hot air back inside the exhaust vents. They aren’t designed for that. He may be helping the attic out a little bit, but he’s short-circuiting his system.

You only want to do one type of ventilation on a roof. Pick a ridge cap, power fan, or can vents. Don’t mix and match.

If your roof is really big, you may have to use two power fans, and you want to make sure they are connected to each other so they turn on at the same time. You don’t want one to kick on and turn the other into an intake. They have to be wired together.

At Roof Life of Oregon, we prefer a ridge vent system. They don’t work on every roof, but if your roof has enough lineal feet, we highly recommend it. There are no dead air spots with a ridge vent, because they go all the way across the entire ridge line. It’s less cutting on the roof, less protrusions and it functions great.

We go to Air Vent Incorporated’s ventilation training every year to stay updated on best practices. I highly recommend going to their website to learn more about ventilation and what may be best for your roof.

If you have specific questions about the ventilation on your roof, just give us a call and we’d be happy to help.


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