I considered Icynene Insulation, but found something better that fits the same application.
From my understanding, Icynene is an open-celled foam. It can absorb moisture and slowly pass moisture.
I used a sprayed-in, expanding, Closed-cell, high density urathane insulation for my house here in MN. The attractions of the higher density, closed-cell urathane were:
1. Highest R-value of any system per inch. About R6 per inch. I put 3.5+ inches in all the walls and rim joist areas for a total of over R-20.
2. Complete moisture seal. With a stucco exterior, I didn't want to worry about moisture from the warm moist interior of the house condensing behind the stucco and causing rot and mold.
3. Complete wind seal. No wind intrusion from the exterior.
4. The closed cell foam provides no surface area for mold to grow on if it does get wet from either interior condensation or exterior intrusion.
5. Being sprayed-in, the moisture barrier is more complete than any piece-meal system of stapled-up poly. The inspectors required poly on the inside surface of the wall anyway.
6. Adds strength and stiffness to the structure. I removed a portion of a wall that had the dense, closed-cell insulation. The foam/wall assembly had to be sawed out in integral chucks. The foam was completely adhered to the studs and the sheathing, and was very dense. All that foam between all those studs made the wall very resistant to any racking or vibration.
7. Best sound blocking. One side of my house is somewhat close to a busy highway. We only hear the road noise if the windows were open.
The negatives of using this technology:
1. Fumes - during installation, the fumes were pretty strong. Nobody else could really work in the house while they were spraying. One installer wore breathing equipment. The assistant appeared to have already lost too many brain cells to care about wearing a protective mask.
2. Re-work of anything in the wall after the foam is installed is a pain in the ****. The foam has to be sawn out with a sawzall or ripped out with the claw end of a framing hammer.
3. The foam, in a fire, can emit more toxic fumes than fiberglass. Also, the foam has to be covered with sheetrock to pass firecode. It can't be left un-finished in a basement, for example.
4. The cost is higher than one would like.
