Detached garage insulation

[notapro]

I am planning on insulating my detached stud walled garage. The garage as a ridge vent with open truss at this time. A plan on putting up OSB on the walls and ceiling. I will have a vent free NG heater running in there periodically. Tyvek wrap is on the exterior walls under the siding. My plan is as follows:
1. Install baffles and use unfaced fiberglass insulation on top of the OSB hung on the ceiling.

2. Use kraft faced insulation in the wall cavities.

Do I need to be concerned about vapor barriers anywhere? Any suggestions for this type of project?

[suemarkp]

Vent free heater meaning it exhausts into the room it is heating? If so, realize that a lot of water vapor is produced when burning NG or propane. I think you may want to use vapor barrier insulation on the ceiling too, else all that water will be condensing in your roof insulation. If you can't find kraft faced thick enough, use plastic sheeting between the OSB and the insulation as a vapor barrier.

[Fischer]

Use 6 mil poly both on side walls and on ceiling, and have a more efficient envelope. This way you'll protect the space from moisture and keep your heat longer. If moisture is allowed to escape and condenses on the OSB, you're asking for a mold and mildew problem.