Double Insulation in a steel building?

[heavytlc]

I am finishing up the office/game room in my steel building. The building is a standard red iron steel framed building. I installed insulation attaching to the z purlins of the metal building. I have r19 in the walls of my building and r25 in the roof. The insulation has a wmp-50 vapor barrier, white reinforced fabric with a foil facing the insulation.
I am not sure how to go about insulating the stud walls.The interior framing is a mix of 2x4 and 2x6 stud walls. It does not sound like a good idea to have a double vapor barrier, so I am not sure kraft faced fiberglass would be right for the stud walls.

What would be the correct way to double up the insulation?

 

[W-Cummins]

Use unfaced rolls that way you will not have 2 vapor barriers. I put unfaced r-25 8" over the wpm-50 stuff.

William...

 

[heavytlc]

I was not sure if I remembered correctly. I was pretty sure that was how your shop was done. What do you think about the insulation in the floor under an attic storage area. It is the ceiling of the kitchen area on the downstairs, up top it is attic storage with no heating/cooling.