If you can vent exhaust to the outside
and use outside air taken in for combustion as our Monitor K-1 heater does in our insulated garage workshop (the heater has been discontinued) there is NO condensation. No tools have rusted in the 12 years we have heated a boat workshop with it with temps below zero outside.
I am glad these units last forever as they are no longer made. You might find them secondhand…they were not cheap new…some one grand.