Update - Mar 30, 2014
I attached the polyiso rigid foam on all exterior wall surfaces. It took longer than it would for most people, largely because I am more of a perfectionist, even for something like this. At first, I applied the glue (PL375) in globs to the back of the foam itself:
It needed to be in rather large globs since the wall was so bumpy and this increased the chances that more of the glue will make contact with both surfaces. As is, quite a few of those globs still never touched, so I didn't do it like that the entire time. It went through a lot more glue than I originally thought, too. See, I originally bought the standard 10oz cans and I assumed I'd be able to glue up three 4x8 pieces per can. I eventually got a 28oz caulk gun and so I returned those and got only a couple of 28oz cans of the glue. It turns out that I drastically underestimated how much glue I'd go through, as the 28oz can (three times larger than my original 10oz cans) only handled 4 pieces. That meant that I would have gone through an entire can for each piece of foam, originally!
Handily, though, I was able to use normal construction adhesive and not the "foam board" crap. That's the blue stuff. I used that some time back and it was absolutely useless. It's needed for EPS or XPS foam, though, as normal construction adhesive will "melt" the foam. Polyiso has an aluminum foil backing which prevents that and so I could use a variant that actually worked.
I pressed each piece against the wall and then put weight on the top of the foam using a 2x6 and the bottom using a piece of slump block:
Yeah, that's a laser level. My wife was incredulous that I'd use a laser level on a piece that will never be seen after the walls go up. Who cares if it's perfectly plumb, she asks? Well... I don't have an answer for that other than I
care and the reason it needs to be plumb is "just because it does."
Note, too, the shims under the bottom. My original plan was to put the foam on a 2x4, so it was 1-1/2" up and level with the top plate. It turns out that the walls aren't exactly the same height all the way around and so the foam sheets wouldn't be flush with the top plate in all cases. I decided, instead, to consistently shim the foam up 1/4" on the bottom and to leave a gap of an inch or so on the top. I would then spray expanding foam on the bottom and the top to fill in the bottom and even off the top.
There was one outstanding area that I wasn't sure how I'd handle until I got to it and that's where the wires snaked down the wall for the exterior coach light, door bell, and outlet box:
I ended up just gluing a panel right over them. I figured that they were hidden behind a wall before and so they would be hidden behind a wall again. After
the glue had cured, my wife brought up the point that maybe the difference is that now the wires are glued in place and before they were free in the stud bay. The latter case would be easier if we ever need to replace the wire. Maybe. On the other hand, the wire is cemented into the wall and so it wouldn't have been trivial to pull it up no matter what.
After the first day (and first can of glue), I decided to start applying the glue directly to the wall. That way, I'd know to hit the high spots and guarantee better coverage. Since it's not hit-or-miss, I also ended up using less glue:
In this case, the laser line actually came in handy for letting me know where to apply the glue. You may or may not notice that my shims are slightly different. I switched to using a length of 1/4" plywood and then inserted normal shims as needed to get the pieces plumb. The 1/4" plywood lengths will later be used when doing the drywall/OSB layers.
At this point, getting all of the necessary 2x6s into position to keep pressure on the foam was becoming increasingly tricky. Each piece is 12' long, so moving them around all of the existing pieces was extremely tricky. It was a veritable forest of 2x6s:
After all of the foam was up, I started on the gaps using Great Stuff expanding foam. I had purposefully left a 1/2" or so gap between the foam in the corners because there was no way of getting those to be tight. I filled in those gaps with foam:
I don't know if you can see it in the picture but there are some areas there where the foam didn't expand very much and left gaps. Those gaps have been a constant problem for me as long as I've used Great Stuff (which is a decent bit). Sometimes it works like a charm and sometimes it barely expands at all. I have never been able to figure out what the difference is.
Well, a few minutes ago, I saw some videos by Dow that might have shed some light on this. They claim that Great Stuff requires at least 50% relative humidity in order to cure properly, or else it will shrink. This is Phoenix AZ we're talking about, and 50% humidity just ain't happening! So next time I'm going to spritz it with some water and see if that helps or not.
I also finished up a can by spraying underneath the panels to fill the 1" x 1/4" gap. That seemed to work fine. I actually have a "pro" gun for Great Stuff which is a lot more precise, but since I have a couple cans of the normal stuff, I figured I'd use them first. I do still need to do the next half of the room.
I likely won't apply the foam to the top of the panels until I build the walls... for reasons.
Oh, I also taped all of the seams with house wrap tape, to prevent air gaps:
When all's said and done, it looks like so:
I still have one full sheet of foam that I don't know what to do with, plus a bit of left over. We'll see.
Next week, I'm going to finish off applying the expanding foam where it could use it. I'll also look into replacing all of the newish white fiberglass with the old pink stuff, since the new stuff will likely fit better in my upcoming interior wall. While I'm at it, I'm going to attach some leftover pieces of drywall to one of the common walls, just to give them more mass (and why not, because it's all scrap drywall that would otherwise go in the trash). At some point SOON, I'm going to need to paint those windows. That needs to be done before it gets too hot.