The molecules of air (which expand during the heating of the kiln) do not carry many BTUs. The hottest the air gets at the output of the motor is about 140°F. Moreover the heat quickly disipates as the vented air moves beyond the output of the motor. It is not much more than a dryer vent.
However, the final decision to use an insulated or heat-isolated device through a wall is up to the individual installer and must follow any local codes.