Mass furnace fired periodically one or two times a day, for approx. 1.5-2 hours. Stein mass stores heat and gives the sakte tilbake the next 12-24 timene. All combustion takes place with høy temperature, something which gives minimal pollution. It would be possible to obtain ut approx. 4-5 kw per hour in an oven with a half-steinsvegg firing two times a day. This allows you to take ut as heat from stein mass or also as hot water Gjennom one integrert heat exchanger.