Cozy Heat OG Thru-Wall Sauna StoveWood Burning Sauna Stove, Up to 18kW The Cozy Heat OG TW is an authentic wood burning sauna stove hand made in Estonia with through the wall design, so the firebox can be filled from outside your sauna. Wood fired sauna stoves create a mild and long lasting heat. Designed for pouring water over hot stones for an intense steam and a more satisfying sauna experience. 12kW for saunas from 210 to 423 cu. ft. 18kW for saunas from 317 to 635 cu. ft. Cozy