Baffles needed in every rafter bay?


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Old 09-12-11, 10:42 AM
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Baffles needed in every rafter bay?

I want to ask a question. I am getting ready to blow insulation into my attic. Do I need the soffet insulation vent installed between every joist rafter or just where the soffet vents are?
 
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Old 09-12-11, 10:48 AM
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I moved your post to its own thread....

No...they don't need to be installed in every bay IF you have adequate ventilation and won't need to add more later.

Seems I've heard that you still don't want it touching the roof out at the edges.....not positive of that.
 
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Old 09-13-11, 03:51 AM
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I would install them in each bay, although there may be a consensus not to do so. My reasoning is any air that is coming in from your soffit vents can actually go laterally as well as up into the baffles. I would rather have a good circulation of air across the board than to restrict it in one area. Besides, if you did decide to reinsulate at a later date, blowing insulation into the un baffled areas would stop this lateral flow.
 
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Old 09-13-11, 05:41 AM
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No question, every bay, especially if you have limited area venting into the soffits. Natural ventilation is poor/slow at best with the motivating force originating from the cold air pushing its way into those soffits through whatever vents you have. Warm air that may accumulate in unvented bays does not rise and exit by itself, it must be pushed out by invading cooler air, thus the need to vent every bay.

In addition, if you can add a block at the end of every bay to prevent incoming air from "wind washing" the exposed end of your insulation it will reduce your heat loss.

The key points are to not fill your soffits with insulation, vent every bay, and protect the insulation from incoming air.

Bud
 
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Old 09-13-11, 05:53 AM
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Guess I was wrong.

Though I'm not sure how the air will move laterally? Maybe I've been living here long enough that I've forgotten how the majority of houses are built. No soffits on 90% of 'em out here.
 
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Old 09-13-11, 06:21 AM
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GG I'm assuming he has vented soffits of some sort and that is where the air will be able to move sideways and then up into each bay. I do agree that there are many homes where venting options defy traditional thinking. Lacking soffit vents then edge venting would be an option.

Bud
 
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Old 09-13-11, 07:08 AM
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I would do every bay if only to allow for the future - what if you want to put in aluminum soffit and ridge vent down the road?
 
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Old 09-20-11, 11:57 AM
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do open attic windows count as ventilation? just curious as i basically have 1/2 a permanently open window in the attic (used to be a fan there and it was filled in very sloppily) and my 2 other windows are open about an inch or 2 for various reasons.
 
 

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