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Old 01-29-2012, 04:23 PM   #1
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How high should soffit baffles be?


About to blow in cellulose insulation to R-49. Going to be shooting for 15-16" I believe.

Only a small part of the house actually has soffits, which is on the front porch area. The rest of the roof doesn't overhang enough for there to be soffits. I can see cracks of sunlight in those areas, however, which are around where the gutters are. Since this area isn't airtight and not putting baffles in could cause ice damns, I'm baffling the entire attic.

If I'm doing 15-16" insulation, before settling, how high should the baffles go? One baffle seems to be in the 15-16" range, so I'm betting I have to do two of them... (I'll have to measure to be sure.) Which means doubling the cost, so I wanted to make sure first.

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Old 01-29-2012, 06:20 PM   #2
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How high should soffit baffles be?


About 12" above the installed thickness to be safe: http://www.buildingscience.com/docum...n-roof-venting
Notice air-seal is step one in that article. FYI: http://www.google.com/url?sa=t&sourc...wWATQw&cad=rja

Use the good stuff: http://www.rateitgreen.com/company/n...-created-equal

https://docs.google.com/viewer?a=v&q...lUasdguH6vaXKQ

Most baffles cut with a utility knife or snips.... the plastic ones are more durable than the foam, and have a built-in top plate space as the first article sited.

Gary

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Old 01-29-2012, 09:56 PM   #3
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How high should soffit baffles be?


If I am reading this right, you have "cold corners" where the wall meets the ceiling, ie, no insulation at that corner. If so, is there anything you can do to address that? If imagine you are going to have water or ice in that corner otherwise.
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Old 01-29-2012, 10:16 PM   #4
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How high should soffit baffles be?


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Originally Posted by jklingel View Post
If I am reading this right, you have "cold corners" where the wall meets the ceiling, ie, no insulation at that corner. If so, is there anything you can do to address that? If imagine you are going to have water or ice in that corner otherwise.
I appreciate your concern! I had a post a while ago about ventilation, which has a decent description of my attic and a bunch of pictures of the exterior of the house and the inside of the attic. You can see this at this post.

EDIT: After I made that older post, we installed two large rectangular gable vents underneath the existing small triangular gable vents. Those aren't in these pictures. Also, for what it's worth, I used Great Stuff to fill in the small gap between the gypsum board and the top plate.

The second to last picture might be the be most relevant to answering your question. I have 40 spaces that need baffles (2 each space so they're high enough), and I put 3 in tonight just to see how it would go.\

In this picture, the gypsum board is on the bottom, and the roof deck is on the top. Deep in the cavity, you can see the top plate. It blends into the gypsum board decently, but it's the last few inches that are slightly darker. Going behind that, there's a few inch gap. The exterior of the house is brick, so I think this gap is above the brick.

The few baffles that I've put in should allow a bit of insulation over the top plate, but as you can see, it's only going to be a few inches.


Does it look like I'm going to have the problem you're referring to, and what steps could I take to better go forward?

Last edited by darlingm; 01-29-2012 at 10:19 PM.
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Old 01-30-2012, 12:05 AM   #5
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How high should soffit baffles be?


Oh, I think I see now. I thought you were seeing daylight from INSIDE the house, which REALLY concerned me. Proceed.
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Old 01-30-2012, 12:42 AM   #6
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How high should soffit baffles be?


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Oh, I think I see now. I thought you were seeing daylight from INSIDE the house, which REALLY concerned me. Proceed.
Depends on your definition of "inside". I can see daylight from inside the attic, but not in living space.

In some areas in the attic, I can see cracks of light looking out where there would be soffit vents if the roof extended out enough. You might be able to see what I'm talking about in this image (which was also in the post I linked to.)

I'm not sure if the crack of blue along the top of the board in this particular picture is actually daylight or not, but it illustrates where I can see daylight in some areas. I can't make out anything, but if I turn the lights off in the attic, I can see some cracks of light. Not sure if it should be this way. Perhaps someone intentionally made it not extremely airtight, to provide some ventilation since there weren't going to be soffit vents in that area.


Last edited by darlingm; 01-30-2012 at 12:44 AM.
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Old 01-30-2012, 01:30 AM   #7
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How high should soffit baffles be?


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Originally Posted by darlingm View Post
Depends on your definition of "inside". I can see daylight from inside the attic, but not in living space.
That is what I gathered. Cracks in the attic, if they don't let water in and are above the insulation, are just vents (unless you are worried about bugs or skinny mice, neither of which apparently cares for nesting in cellulose treated w/ borates). That won't stop fliers from building nests above, of course.


Last edited by jklingel; 01-30-2012 at 01:31 AM. Reason: removed photo
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