If your in a dry climate like Phoenix it makes sense, wet climate like Houston, not a good idea. Not knowing your climate, those two examples of where you could use the foam may be helpful. Trapping moisture in a wet climate like Houston would not be good for the house.
From: Strat <stratmister@gmail.com>
To: DoIt_Yourself@yahoogroups.com
Sent: Tuesday, January 22, 2013 7:06 PM
Subject: [DIY] Closed Cell foam insulation
To: DoIt_Yourself@yahoogroups.com
Sent: Tuesday, January 22, 2013 7:06 PM
Subject: [DIY] Closed Cell foam insulation
Recently I read a debate in fine home buildiig mag on benefits of retrofitting an old homes exterior with 2-inch closed cell "rigid sheets", y'all can look it up if you're interested in reading it. But the long and short of it is:
My old home which probably has no kind of insulation in the walls and that makes the house hard to heat during winter.
Having researched options, I see basically 4 possible approach to insulating the walls:
1-spray closed cell foam between the studs and button up with new siding.
2-spray open cell foam, which costs less but doesn't have vapor barrier properties of closed cell.
3-fill the cavities with damp cellulose
4-cover over the studs with 2" sheets of rigid foam sheathing, tape the seams, cover with a wrap, then apply the siding.
Its this last approach that's got me fired up.
I don't understand why you would build up the exterior thickness over the studs by 2 and 5/8, that's crazy.
Not only does this pose new problems for re-flashing all the doors & windows, but also I wonder how the heck is the exterior siding going to attach to the studs with 2 and 5/8 space between them!?
It seems 4 inch galvanized screws would be the only option, heck you can't secure the siding to foam!!
My preference is to shoot closed cell foam in the wall cavity every 16 inch. This ensures all the walls, electrical outlets, sills and ceiling transitions are sealed tight with a vapor/moisture barrier which offers better R value per inch than the other options.
You can then wrap that with Tyvek and nail in James Hardi boards with a nail gun, bang bang bang, you're done.
No need to spend a lot of extra money on foam fastners, and 4 inch galvanized screws for securing siding to the studs. Best of all, I preserve the original thickness over the studs and minimize the need for custom flashing around windows.
There is yet another evil which is sizemic movement here in California the ground moves! These foam sheets are not speced to be sheer walls and I would not bet that in a year or two the tape that seals all those seams is going to hold "air-tight", in fact I bet it won't.
In closing I'm no expert, just a home owner, but I honestly don't see the logic in wrapping the house with rigid foam sheets.
My old home which probably has no kind of insulation in the walls and that makes the house hard to heat during winter.
Having researched options, I see basically 4 possible approach to insulating the walls:
1-spray closed cell foam between the studs and button up with new siding.
2-spray open cell foam, which costs less but doesn't have vapor barrier properties of closed cell.
3-fill the cavities with damp cellulose
4-cover over the studs with 2" sheets of rigid foam sheathing, tape the seams, cover with a wrap, then apply the siding.
Its this last approach that's got me fired up.
I don't understand why you would build up the exterior thickness over the studs by 2 and 5/8, that's crazy.
Not only does this pose new problems for re-flashing all the doors & windows, but also I wonder how the heck is the exterior siding going to attach to the studs with 2 and 5/8 space between them!?
It seems 4 inch galvanized screws would be the only option, heck you can't secure the siding to foam!!
My preference is to shoot closed cell foam in the wall cavity every 16 inch. This ensures all the walls, electrical outlets, sills and ceiling transitions are sealed tight with a vapor/moisture barrier which offers better R value per inch than the other options.
You can then wrap that with Tyvek and nail in James Hardi boards with a nail gun, bang bang bang, you're done.
No need to spend a lot of extra money on foam fastners, and 4 inch galvanized screws for securing siding to the studs. Best of all, I preserve the original thickness over the studs and minimize the need for custom flashing around windows.
There is yet another evil which is sizemic movement here in California the ground moves! These foam sheets are not speced to be sheer walls and I would not bet that in a year or two the tape that seals all those seams is going to hold "air-tight", in fact I bet it won't.
In closing I'm no expert, just a home owner, but I honestly don't see the logic in wrapping the house with rigid foam sheets.
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