I have an existing barn in Vermont with exterior metal siding and R-19 fiberglass insulation with a plastic sheeting (4mm polyethylene) vapor barrier on inside of 2×6 structural framing.  I want to add 1 1/2″ of rigid insulation on the inside face of the horizontal strapping that is fastened to the poly vapor barrier and finish with 5/8″ plywood on the interior (see attached detail). 
Question: Will I be creating a moisture/condensation issue inside the wall construction by adding the additional rigid insulation on the warm side of the vapor barrier?
Thanks in advance for any/all feedback!