Since the house is locating in a mountainous area, it was already cold enough to use this firewood stove. Usually Japanese old houses are designed to survive summer heat and very cold in winter time. We developped culture enduring cold weather rather than inventing energy comsuming heater that can warm up whole house. I was surprised when I was in Denmark. that once we went inside the buildings or houses, whole building or house was heated up and it was enough if we were wearing like spiring time.