I am looking to insulate my garage. There are a couple things that are throwing a kink into my plans, however, the second question may answer the first.

My first question is...I know that you're supposed to put a vapor barrier on the heated side of any insulation and that the vapor barrier is supposed to be continuous. How are you supposed to do this in a room that is already finished? I have to insulate from the garage (unheated area), so is there any way to do this using conventional insulation?

The second question, which probably answers the first is...There are also heating ducts in the garage ceiling. What's the best way to make sure that the maximum amount of heat gets to the registers from the furnace?

I think my best bet is going to be a closed cell blown in expanding foam insulation. If this is the case, am I correct in thinking that I don't need a vapor barrier with a closed cell expanding foam insulation?