Insulation over and over...
I also posted it under article titled "Monitoring Moisture Levels in Double-Stud Walls", but figured some other people may read it here.
I have done quite a bit of reading around the Internet and I am still little confused. I own the house on uninsulated concrete slab (it will stay like this at least for some time, no basement). House had the second floor addition done in 2008, walls should be R15 and attic R30. Studs on both floors are 2x4,16" apart. The problem is the first floor. It is 60 years old, and has poor rock wool insulation inside. Outside it has probably asbestos siding covered with vinyl siding. I do not think there is any rigid foam in between. I am in NY, Long Island, which can be pretty dump in summer time, zone 4A.
I would like to remove sheet rock (walls and ceiling) and insulate the walls, and ceiling\rim joists (only where they “meet” outside wall). I have the following concerns (let’s say that money is not a concern in a sense that I would like to stay frugal, but I am willing to pay more for better and long standing solution\comfort of my house):
1. First, I wanted to fill all stud cavities with closed cell foam. However, I am afraid that I will create vapor barrier, and as far as I understand reading on the Internet I should not do it, as the moisture will transfer to studs and can create mold problems. Is that, correct? Plus it is expensive and supposedly not feasible in economic sense as I would lose its R value do to studs...
2. Second, I was thinking to spray 1” or so of closed cell and fill the rest with open cell. Is that good option? Should I be careful again not to create vapor barrier by closed cell foam, so keep it thin? I also read that closed cell needs to be sprayed in at least 2" layers...
3. Third option I was considering was this:
However, I would space horizontal 2x2 by 24” to further minimize thermal bridging. Can I, alike in #2, spray 1" or 2" closed cell foam first and then fill the rest with open cell foam (I think it would be to thick in this case and act as vapor barrier too), or rather cellulose (as pictured on the website)? My wall would be 2x6 only so I hope moisture problems related to extra thick walls will not apply? Do I need to calculate dew point here?
4. I am afraid of cellulose settling. Is it a big deal nowadays? It somehow makes me resistant to use it. Am I exaggerating? I saw cellulose being recommended here multiple times… so maybe I should just go with 2" of closed cell and then cellulose...
5. In all cases I would NOT add vapor barrier on inside.
6. If none of the above is good solution, what would be the best way to achieve the highest possible R value for given circumstances (also keeping economy in mind)? I would like to avoid removing exterior siding.
I greatly appreciate any help and suggestions!
Posted Sun, 12/29/2013 - 21:58
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