Attic venting without soffit help!

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  #1  
Old 10-19-16, 04:09 AM
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Attic venting without soffit help!

Im insulating my attic, removing the r11 and replacing it with r30. My concern is the venting. I have a finished room with 2 knee walls on both sides. There are 2 gable vents and a continuous ridge vent. Is that sufficient? My house only has soffit on one side only which is currently not vented.. What are my options in terms of properly venting this house? This has left me stumped! Thank you in advance!
 
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  #2  
Old 10-19-16, 04:34 AM
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Are there soffits along the outer edge of the kneewalls?
 
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Old 10-19-16, 05:03 AM
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Theres soffit only on one knee wall
 
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Old 10-19-16, 05:08 AM
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Measure or estimate the area of your vents. There are simple formulas and online calculators to help determine an appropriate amount of ventilation.
 
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Old 10-19-16, 05:49 AM
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Dgust, you obviously know the basics of the issue or you wouldn't be asking this question. Here's my thoughts on solutions.

If the soffit you mention in your original query can be reached from the attic, there are many products available to add ventilation. They come in numerous shapes and sizes. Just cut the hole and put up the vent. There's nothing to it; check out some videos. The decision on which to use and how many will be based on need. Many calculation tools are available online. Don't completely cover the soffit with insulation; use rafter / baffle vents to allow air movement.

If the soffit is only reached from the kneewall, you'll have to get behind the wall, perhaps from a closet. Use rafter / baffle vents between the kneewall and the attic and follow my comments, above.
 
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Old 10-19-16, 06:18 AM
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Thank you for your replies. I understand the baffles and how to make a soffit vented and all of that. What my concern is having a soffit on only one side. The other side without the soffit will not have any cool air between the insulation and sheathing and possibly leading to moisture problems down the road. Do I put baffles there also or have to create a vent somehow for fresh air to flow in? Or just insulate normally and pray for the best?
 
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Old 10-19-16, 06:23 AM
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You should have a source of fresh air at a low position, then a path for it between the insulation and the bottom of the roof up the slopes. Any picture would help.

Bud
 
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Old 10-19-16, 06:48 AM
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See, soffit on one side of house. What do I do with the right side
 
  #9  
Old 10-19-16, 07:22 AM
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Unless you have an additional problem you haven't mentioned (perhaps icing on the roof), there's no need to do anything on the right side. If your concern is for some sort of horizontal balance, that's nice but not required.

The idea of ventilation is for air to circulate in and out of the attic. The source of the air intake (left, right, or both) is not critical.

Balance is critical when it comes to intake and outflow /exhaust. The intake must at least as much as the outflow.

Assuming you can access behind the knee wall, you can add soffit vents from the left together with baffles between the knee wall and attic as I mentioned earlier.

If you have a specific issue on the right, let us know. One last point, sealing is at least as important as insulating. Given your information, air must be coming into the attic from someplace so make certain you seal properly.
 

Last edited by Tony P.; 10-19-16 at 07:45 AM.
  #10  
Old 10-19-16, 07:50 AM
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One more point, you have two types of exhaust/outflow vents, which many people consider a no-no. The reason is instead of both systems working in concert, one (probably the gable vent) becomes an intake vent. This means weather can come in from outside. Without getting into air dynamics, a proper intake vent avoids this.
 
  #11  
Old 10-19-16, 08:58 AM
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Okay that makes the most sense. I guess as long as there is air flow there will be no reason to have any humidity issues. I will baffle and insulate the left side ad well as add continuous soffit vents. On the right side I will just Insulate between the rafters normally. It's safe to say I should cover up those gable vents ad well?
 
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Old 10-19-16, 09:12 AM
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For the side without soffits they have edge vents that go under the shingles. They also have vents that go behind the fascia board or replace the fascia board.

My thinking differs from Tony's, I'll just list them. I'm not picking on you Tony as much of what you said is normal guidance within the roofing and ventilation industry. Unfortunately, that advice has been wrong for many years. Maybe another thread so we don't drift here.
1. @ Tony: "there's no need to do anything on the right side."
**Moisture is one of the major concerns and ventilating the left side only will do little good for the right side. Not sure of your climate region so not sure what issues you are facing as Tony asked.
2. @ Tony: "The source of the air intake (left, right, or both) is not critical."
**It is important to have air flow on both sides.
3. @ Tony: "Balance is critical when it comes to intake and outflow /exhaust. The intake must at least as much as the outflow."
**Actually it is not critical, merely a target that provides guidance for a wide variety of homes. As varied as 75/25 (or 25/75) will still work.
4. @ Tony: "Balance is critical when it comes to intake and outflow /exhaust. The intake must at least as much as the outflow."
**Correct, but to clarify, that is air sealing between the house and attic. References for that are available.
5. @ Tony: "One more point, you have two types of exhaust/outflow vents, which many people consider a no-no. The reason is instead of both systems working in concert, one (probably the gable vent) becomes an intake vent."
**This is referred to as the "short circuit theory" but in reality, air follows the pressure across those paths, intake and exhaust. There are at times reasons to eliminate the gable vents, like rain and snow, but if that hasn't posed a problem so far, leaving them in place just increase the total ventilation.

Below the kneewall is also an important area to block the cold air. Here is a related link.
Two Ways to Insulate Attic Kneewalls

Bud
 
  #13  
Old 10-19-16, 09:30 AM
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That's what I thought from the beginning and why I was so puzzled with this in the first place.. I live on long Island NY by the way. And I plan on insulating the rafters as the space behind the knee walls will be for storage.

I feel like my 2 options are to leave the vents as is)( 2 gable vents and a continuous ridge vent) and insulate as it was before only with r30 instead of r11. But I'm scared that since it will be properly insulated it could open up a potential humidity and moisture problem (possibly add a fan? ) . Which leads me to option 2, make my non vented soffit vented and add the vent under the shingles and baffle from the soffit up and so on and so forth. That is where I'm stuck.
 

Last edited by Dgust; 10-19-16 at 10:06 AM.
  #14  
Old 10-19-16, 10:48 AM
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You have a couple of details to work out. One, you can't install fiberglass insulation directly against the bottom of a roof. Moisture laden air works its way through to the cold roof with disastrous results. So it comes down to providing an air channel from soffit to ridge or installing sufficient closed cell foam insulation, rigid board or spray-in, so that the inside surface of the foam insulation never gets cold enough to form condensation. I'll add a link on insulating cathedral ceilings.
How to Build an Insulated Cathedral Ceiling | GreenBuildingAdvisor.com

Second would be meeting code requirements, which is difficult without a major renovation. To be complete I had to mention code compliance and won't bug you again.

Third, insulating the rafters, essentially from soffit to upper attic space means you should at least partially heat the kneewall space. If left isolated from the heat even though it would have its own insulation, it will get very cold in there and present a potential condensation issue. Even a closet on an exterior wall that does not have a source of heat can have a mold problem.

In addition, if you want to insulate the bottom of the rafters and choose to ventilate above, you will need ventilation in each rafter bay.

Not sure what the outside looks like where the no-soffit roof terminates above the outside wall, but here is another option, a ventilated fascia board.
GAF | Cobra FasciaFlow Vent (Attic Intake Vent)

Bud
 
  #15  
Old 10-19-16, 01:22 PM
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Thank you! I think I'm going to put the vented facia board along the no soffit side and vent the soffit side properly. I'll then add baffles and insulate accordingly. Now the last question is do I cover up the gable vents?
 
  #16  
Old 10-19-16, 03:26 PM
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No need to cover them, they will act as additional exhaust capacity, how much depends upon the height of the attic, height of the gable vents and the amount of other high and low venting. But the actual vent area needed can vary SO much that basically it comes down to more is better, unless the snow and rain start coming in. But since they will be acting as exhaust vents that would be unusual.

The part I don't like is when the roofing industry or others insist the gable vents be removed and that results in added costs that could have been spent elsewhere.

Your call, but I would leave them as is.

Let us know how that vented fascia works out.

Bud
 
  #17  
Old 10-19-16, 05:48 PM
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Thank you very much for your time and help. I'll keep you posted!!
 
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