Metal woodstoves are a significant improvement over open fireplaces from the standpoint of producing more usable heat. They limit incoming air, thus avoiding heating air not needed for combustion. Another improvement: they use a lengthened heat exchange pathway to improve heat transfer from the heated combustion gases before they exit the chimney.

Unfortunately, metal woodstoves must operate at low, inefficient, and polluting combustion temperatures. Why? Because wood combustion requires high temperatures to be clean and efficient. Wood burns starts to burn cleanly at around 1200 degrees Fahrenheit, with continuous improvement up to about 2000 degrees. Cast iron begins to glow red and fail at about 1200 degrees. See the problem?

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