You have moisture issues, and it seems like they may be serious.
If they installed 1/2 pound Icynene foam it works like a sponge if the house has moisture issues, and vapor and air barriers were not installed correctly. Moisture could be from unvented bathrooms, condensation in the basement from having no vapor barriers...not being there the list goes on.
You need a professional building scientist to give you an evaluation NOW.
I hope I am totally wrong in my opinion...but I have seen it many times.
Try a good American Society of Home Inspectors, ASHI
home inspector that deals with these issues, or try Building Science Corporation
for another avenue. Be prepared to spend some $$ on these folks, and make sure you document everything with #s and who you talked to. And lots of pictures as you go. If you have a lawsuit, you will need these down the road.
Hope I am wrong, but good luck.