It may be moot. The product is probably called Tyvek. Its patent belongs to Dupont, Inc..
You can contact Dupont, and when you do, let them know where you live and what's 'behind' the unwrapped area in question. Let them know if it's heated or not, let them know if it's livable space or not.
If you have a Real Estate Attorney handling your contract w/the Builder (you do have one, no?), then ask him/her what your options are. Perhaps hiring a New Home Inspector of your OWN choosing is a good idea too. Just don't sign ANYTHING until you get your answer.