We have almost completed the cob bench for thermal mass incorporated into our yurt stove. When we truly finish it will be a thing of real beauty but for now, it is there to slowly release heat that would otherwise be lost up the chimney. The flue goes through the cob therefore heating it up prior to going into the chimney proper. Watch this space, by next Summer the yurt will also have photovoltaics for lighting and power and a solar/wood fired shower.