Here's my situation which I hope someone has a solution for. My house is built on a full basement. Half of the basement will be an uninsulated garage. The floor above the garage will be insulated with roll fiberglass. Since the house floor sheathing is down I can't put the insulation in from the top so that the vapor barrier is facing the warm side of the house. How do I handle the vapor barrier situation? Thanks.
One option, albeit time consuming, would be to purchase a vapor barrier such as felt paper, and install it between the joists from below. Using an unfaced insulation below the vapor barrier should then solve your problem. To hang, look into getting insulation hangers.