jar: no vapor barrier of any kind in basements. you WANT your house airtight, but vapor open. air seal like a maniac. water proof and cement board around the tub/shower area. leave the fiberglass crap at the store, and see if you can find some rock (mineral) wool, cotton, or wool batts. spend some time reading on buildingscience.com if you care to, too. (btw: if you have poly against kraft paper it will not count as a "double vb" because they are against each other. one inside and one outside is the killer situation, but don't use any poly; air seal instead).