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My house does not have soffit vents. The overhang at the eaves is too small. The ceiling leaks were sealed up by an HVAC company about 10 years ago. They also blew in insulation to an R30 level in the attic. There are gable vents (22” rounds) on both ends. A roofing company just put a new roof on and added a ridge vent. Am I ok to leave it alone? Do I need to put in a gable fan for air intake?

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    Unfortunately, continuous ridge vent and gable vents aren't an ideal combination when using a fan--one short-circuits the other. Are you finding that attic temps are unreasonable? That's the key--not what some yahoos on the internet think.
    – isherwood
    Aug 19 '20 at 16:05
  • Attic temps are not really all that hot. So, if I just leave it as is with the two gable vents and the ridge vent, will I be ok? Or will I have big problems in the future with this setup?
    – ERASERGIB
    Aug 19 '20 at 19:17
  • I was just wondering if I would end up with moisture problems in the future due to my current setup
    – ERASERGIB
    Aug 19 '20 at 22:17
  • That's unlikely, but I don't know where you are or what your climate is. I'm in Minnesota where it's quite humid and can be very rainy and we don't really have attic moisture problems where there's as much ventilation as you describe. I'd expect that you're ok. You should keep an eye on it, though. Every situation is different and I can't say.
    – isherwood
    Aug 20 '20 at 0:18
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I live in Oregon and gable vents work fine here if you needed more flow I would suggest a solar exhaust fan in the middle of the house to create more flow but if you don’t have excess heat your system is working fine. I have added exhaust fans to my homes as it reduces my cooling costs.

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  • You downvoted me so I’ll downvote you because your answer is speculation not mechanical engineering, like in the code.
    – Lee Sam
    Feb 17 at 5:01
  • Thanks for letting me know, I leave comments when I down vote But now your down vote count is 2 so it was not me to start with , so you have your explanation @lee sam
    – Ed Beal
    Feb 17 at 14:05
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The Code requires Attic Ventilation to be “cross ventilation “ and shall be 1/150th the area that is to be vented. (See ICC R806 Vents.)

However, there is one exception: The attic ventilation can be reduced to 1/300th the area to be vented provided one of the following items are met:

  1. a Class I or II vapor retarder is installed on the “warm-in-winter” side of the ceiling, or

  2. not less than 40% and not more than 50% of the ventilation is located in the upper portion of the attic. The upper portion is defined as: “Upper ventilation shall not be lower than 3’ below the ridge or highest point of the roof. “ (See ICC R806.1.2.)

So, if your attic is 20’ x 40’ then the area is 800 square feet. So with ridge vents you need 1/300th the area, or 800 / 300 = 2.67 square feet of vents. You can calculate how many square feet of vent you have and know if your venting meets the Code minimum. If so you should be ok.

So, you can see there is clearly a benefit to having ridge vents, gable vents, etc.

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  • Sorry but this is a really bad answer that implies that the more vents the better. Code cited isn't helping, it is actually producing a good system while staying in code - which any good system will meet code. The last sentence is a disaster. Gable vents would reroute air and make the ridge vent less effective. I don't think anyone from a roofing or "green" company has ever prescribed both for one of my homes (and they sure would to make extra $$$). A bad answer is wrong, a dangerous answer costs the owner money while making their home worse. You should delete this.
    – DMoore
    Feb 17 at 4:32
  • @DMoore You downvoted my answer because I cited requirements cited in the Code. Btw, this is the same code you use in Oregon, I know because most of my work is in Oregon. You say things that you can’t substantiate, like “any good system will meet code”. What do you mean...and what is your definition of a “good system”? The Code defines it and sets exact measurements for you to meet. Then you say it’s a “bad answer”. How can it be a bad answer if it’s citing the code. I suggest you re-read and study my answer.
    – Lee Sam
    Feb 17 at 4:54
  • You are having problems reading. I downvoted because it is blatantly wrong - you should not have ridge and gable vents. Quoting code doesn't qualify for a right answer.
    – DMoore
    Feb 17 at 6:14
  • @DMoore You’re not understanding the code. The code outlines how and what proportions to use ridge and gable vents. If you don’t understand, let me know and I’ll walk you through it.
    – Lee Sam
    Feb 17 at 6:53
  • Well thanks Lee. Afterwards I will go through some 6th grade level reading comprehension. Your answer is so wrong that I actually said something in comments. It is really that black and white.
    – DMoore
    Feb 17 at 7:28

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