This Greenhouse heater we built in Montana has a number of successful experimental features that make it work well in wet conditions like a greenhouse or outdoors. First there is no cob that can get wet and turn to mush. Second is a horizontal stratification chamber that can be placed in a bench in a greenhouse or in the ground underneath the floor of the greenhouse where it can heat things evenly. Third is additional insulation in the barrel surrounding the heat riser to direct as much of the heat as possible into the stratification chamber down in the mass. Lastly instead of a standalone chimney we brought the exhaust back up through the insulated vertical barrel right next to the heat riser so even when the stratification chamber is filled with a "cold plug" of gasses chilled by frozen ground we can still get the exhaust warm and pulling.