I've been working on my garage project and I'm about to the point of
installing insulation on the garage ceiling. The joists between the
living space above and the garage are 22" inches tall and manufactured
from 2x4's. Inside them is the plumbing, electrical and most of the
hvac flex ducts for the room above. I also plan on insulating the
garage walls. I have insulated garage doors on the front and back but
the front one is big, 20x9. The subfloor above is tongued osb.

Does it really matter which way I put the facing on the insulation
between the garage ceiling and the floor above? I know the vapor
barrier is supposed to be against the floor but i's going to be a
whole lot easier to install it with the paper on the garage side as
that will let me staple the paper to the bottom of the joists.
Otherwise I have to figure a way to hold the insulation up while I
install wallboard on the ceiling.