The Compost Heater Silo is the central part of an inhouse compost heater. The composting process is run in an airtight silo, placed in an appropriate part of the building. The produced heat can be distributed by a heating circuit, whereas a simple model of such a compost heater silo does not require a water circulation, radiating the heat directly to the interiors of the house. In autumn the silo is filled up with fresh biomass, after which the silo delivers comfortable heat all winter long.