I was just looking around on ebay and saw a "Masonry Heater" mentioned. I know the spelling is incorrect, but that is the way it was listed. It is made by Heiss Heaters and is said to have secondary combustion. The model shown is not listed as a boiler even though it is and is said to have secondary combustion. You can see it at www.heissheaters.com. I was really surprised by the price as it is less than half of a common gasification unit. They are talking about ceramic masonary which I assume means this unit is made from refractory ceramic. They also claim that due to it's "thermal mass", it has the equivalent of 1000 gallons of storage. I have to say all the numbers sound impressive but I don't know how well this would hold up in the real world. Just wondering if anyone has seen or heard anything about them. It sounds like a good theory, but I don't want to be a guinea pig. Also, I am in no way affiliated with them but just thought the product was an interesting concept.