spray in air seal?


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Old 04-07-13, 01:31 PM
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spray in air seal?

While working in room in my 113 year old home in MD, I found a room without insulation. It is small closet and I just decided to remove drywall and insulate it and put up new drywall (only 3 sheets). but the sheathing is actually 1x boards of various widths-average about 3". So trying to get air seal (they are not tongue and groove), is very hard. using caulk would talk a long time and would really use a lot. I wanted to get something to spray in just for air seal and then use batts for insulation. any ideas? what i have found is very expensive $700. I have insulation company coming to give me price for spray in foam for walls in crawlspace so will get them to give estimate for this as well, but wanted to see other options for this small area.
 
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Old 04-07-13, 02:45 PM
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If the SPF company is already going to be there for the crawl and attic, that additional space should be relatively cheap.

You could also cut and cobble rigid foam into that space and seal the rigid to the interior stud wall.
 
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Old 04-07-13, 09:45 PM
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the sheathing is actually 1x boards of various widths-average about 3". So trying to get air seal (they are not tongue and groove), is very hard.
The exterior sheathing should not be air sealed.
 
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Old 04-08-13, 07:13 AM
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Nash, the exterior sheathing can be an air barrier, but it needs to be permeable to allow drying to the outside. Plywood is a good example of an air barrier that is not a vapor barrier.

If they flask that area with foam there is a risk of the foam expanding out through those same gaps. Another approach would be to line the cavities with a house wrap and then fill them with Roxul. The Roxul is very dense and with the house wrap it will prevent any air infiltration, yet still allow drying to the outside.

Bud
 
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Old 04-08-13, 07:29 AM
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the exterior sheathing can be an air barrier, but it needs to be permeable to allow drying to the outside.
Yes, of course. That's what house wrap does! I confused the two. Sorry 'bout that.

Hammer, how many of the walls in this closet are exterior walls? Those are the only ones that need either a permeable air barrier or insulation. And what are you doing in or above the closet ceiling?
 
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Old 04-08-13, 08:19 AM
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2 walls are exterior. the ceiling has insulation, although when all done with addition I am going to blow in some more in attic. I have used the roxul safe and sound for sound insulation so I am familiar with the rock wool. It was expensive and hard to get-lowes had to special order it. I will discuss with insulation company about possibility of foam getting out cracks and expanding against siding. see if they have very low expanding variety. thanks for your input. Hilti used to have spray foam at home depot but they don't anymore.
 
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Old 04-08-13, 11:51 AM
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I would forget the foam and install housewrap against the exterior sheathing, wrapping is from one stud bay to the next.

the ceiling has insulation, although when all done with addition I am going to blow in some more in attic.
How's the ventilation in your attic? Do you have a plan for keeping the loose insulation from blocking your intake vents?
 
 

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