Wood is vigorously burned in a compact refractory firebox in a short time, cleanly and efficiently. The fluegasses are baffled to pass over a large stone mass before exiting the chimney (counterflow principle). After the fire the damper is closed and most of the thermal energy is retained in the soapstone mass, which continuous to radiate the heat evenly and steadily over a period of time long after the fire has gone out. This reduces wood consumption as well as emissions. This in contrast with the typical open fireplace in the Irish and English tradition. Since the opening is large, the flue must also be large and the heat – often more than is produced by the fire – is lost up the chimney.