I’m helping a friend with his new convention center. The building has cement walls. The city came through and forced him to put two inch rigid insulation on the cement. So the insulation is both glued on and nailed on. Would it be ok to put drywall on the insulation? So it would be cement-insulation-drywall, no wood at all. We would glue the drywall on to the insulation. Walls are 80 feet long, 24 feet high. Any thoughts and or ideas would be much appreciated. Thanks in advance.