vapor barrier necessary?

[mx500]

Hey guys, I just bought a new house with a 30x52 pole barn. The walls are already insulated and finished with osb. The ceiling is done with osb also, but only partially insulated (office area 10x15), and no vapor barrier. Am i limited to using faced fiberglass insulation to insulate the rest of it? This is in michigan where it gets very humid in summer, and will be heating it in the winter with a 65000 btu propane heater.

 

[phbsales]

Any area that is going to be conditioned (heat or cool) is going to need a vapor barrier facing the "warm in winter" side of the area. If you wanted to, you could also use unfaced insulation batts and staple a sheet of 4 mil poly sheeting over it as a vapor barrier.