[jordanb]

Closed cell foam will trap moisture underneath it. When sprayed on wood which is naturally moist that water will have nowhere to go. Any delaminations of the foam from the substrate will form pockets where wet will concentrate, and as the foam breaks down it becomes acidic.

If I were to sprayfoam something I would only consider using open cell foam. If I were to use other impervious zero-perm insulation materials like rockwool I'd only do so with dimple board to allow air underneath. The small loss of efficiency is a necessary tradeoff for giving the moisture which will always be there a path to escape.

[sbradford26]

Spray foam doesn't remove the need for a designing a proper insulation and moisture barrier system for the building. If you spray foam an interior wall with closed cell foam you most likely will add something to allow the other side of the wood to breath.

Choosing where your moisture barrier line lies is typically easy in new construction but does get tricky with retrofit situations. It sounds like the biggest issue from the article is that they are taking what were vented attics and converting them to non-vented attics with spray foam. The issue isn't really the spray foam, the issue is converting an attic without proper understanding of venting and moisture barriers.