HUUM HIVE FlowWood Burning Sauna Stove, 9. 8kW The HUUM HIVE Flow Sauna Stove has an innovative design, ensuring that 75% of the heat from the firewood directly heats your sauna rather than escaping through the chimney. It stands out as one of the most efficient and environmentally sustainable heaters for sauna rooms from 282 to 635 cubic feet (CF). Features Wood burning Unique design Economical wood use Low environmental impact Mild and long lasting steam