This was really fun to build. We really stretched the limit with six drums in the
underground bell (stratification chamber). If I did it again I would cut it down to 5 barrels so there is more heat left in the chimney at the end. The chimney going up through the vertical barrel and being heated really makes a difference in pulling that big plug of cold air out of the bell. I envision this being used in a
greenhouse embedded in the floor or in a pebble mass bench so you can
water seedlings on it. That doesn't work with a
cob bench.
I have built a similar one in a cob bench in a
straw bale schoolhouse near Cleveland Ohio and a smaller one in my house. The bell provides a nice even heat and costs a lot less time, money and hassle to build than the pipe in the cob bench thermal mass.--Uncle Mud