Originally Posted by just jim
Couple of questions...
If you were using open cell foam throughout your house, how did you end up with closed cell foam in the theater?
If you ended up with 4 - 4.5" of closed cell foam, either they have no idea what they are doing or they sprayed in two passes with time in between. Spraying 4.5" of closed cell generates so much internal heat that it could actually catch fire!
FYI Any wires, gas lines (flexible) or anything that is not absolutely rigid has to be fastened to "something" so that it does not move!!! Especially 2lb foam (closed cell) will push them out and you ain't going to do anything about it later. The 1/2lb (open cell) will need to be trimmed and any wires beyond the face of the studs will get damaged. An experienced sprayer can hold the loose wires in place while he sprays one side of the stud space, by the time he is coming back up the foam is set and will hold the wire in. But don't rely on this happening. Fasten everything!
Closed cell foam is a vapour barrier if it wraps around the back of the stud, completely. If you have exposed wood on the back side of the stud, you need a super 6 mil poly vapour barrier. Wood is considered permeable to moisture. Open cell foam is not a vapour barrier.
Closed cell foam is rigid and transmits sound very well. Open cell foam has more of a deadening effect.
Closed cell foam actually deteriorates over the first few years, as the cells pop, lowering the effective R-value. Open cell foam deteriorates to a much less degree, losing less R-value. After 5 years you would be questioning if the extra dollars were worth it. Don't get me wrong there are times when the closed is the better choice.
Unlike the spray cans of foam, these two-part foams are expanded and set in seconds.
Yes, it was done in at least two passes. I wasn't there for all of it, but I did stop by, before going out of town after they had done just a small part of the room, and I would guess they had done about 1.5"(on average) lift. They were supposed to make another pass and bring it to 3", 3.5" tops.
What happened on the second lift was it was very non-uniform. So, in an given stud bay, half of it might have been close to the 3 - 3.5" mark, but then there were large sections that were out close to the face of the 2x6. Again, since I wasn't there, I'm not sure exactly how they managed to screw that up. Bottom line, once it was set, and they didn't have any tools to remove it from within the stud bays (a pain, but much easier to simply trim back to stud faces), that left us with our problem and not much time to address it.
On choosing closed for the home theater it came down to a few things. Since I was only getting 3 - 3.5" of space to foam, I opted for closed cell, because it has a higher R-value (even aged, based on what I have read) than the open cell. The 3 - 3.5" of closed should roughly equal the 5.5" of open used else where. Now, while you could argue since I was also going to have R13 batts, I could have gone with open and the batts and been the same as the 5.5" of foam elsewhere -- which is true. However, since I already knew this "bonus room" location was going to be a challenge to cool, I wanted extra r-value.
Also, the other advantage I saw to closed cell was that if they got thin in any spots with the open, I might not even have a good air barrier, where closed cell is a vapor barrier at 2.5" or so, so it would definately be a good air barrier.
On the vapor barrier, I don't really need it, since I went with Zip system on my house, so there is a vapor barrier all around the house. That said, based on what I have read on building sciences foundation and other places, they do claim that studs act as a vapor barrier and that when used with closed cell foam, 6 mil polly isn't needed. It's been a while since I read that, so I couldn't point to exact articles, but I did read it in several places.