Pete:
Any type of finish only slows the migration of moisture, so the owner needs to maintain the average moisture content of the room below that which would support growth of mold etc. The designer of the mechanical system should be able to accomplish effective humidity control. Put a disclaimer in your contract that states something to that effect. I assume that there will be other non-structural materials in the room that would not fare well at excessive relative humidity. Air leak sealing is also very important in the building envelope.
One frame was salvaged and regraded material with hidden steel reinforcement, others were most often white pine.
