I think we missed something. To hold the loose fill before drywalling, you must have something there. If he said to put plastic up, hang the drywall, then loose fill, it makes a little more sense. I have not seen plastic vapor barriers in Illinois for at least 20 years. If your local code requires it.all you can do is comply. Vapor barriers are only what they imply,to trap moisture so it can deteriorate the cavity and promote mildew,mold and water damage. I would ask for a code book before putting up ANY plastic vapor barrier.