I live in a large barn-style house with a garage on the first floor in the land of ice and snow. Heated with wood, oil backup for years. Always burned 10 to 12 full cords per year along with 300 gallons of fuel oil (big place, leaky garage doors). Then I found a lightly used Madawaska brand gassifier boiler (circa 1980). I bought it, brought it home and rebuilt it, made a storage tank to store lots of water and fired it up. Wood consumption dropped to 7 full cords, with no oil usage at all. Paid for itself the first year. I must clean the boiler thoroughly every two weeks because it needs to breathe. Never have had to clean the chimney, even burning off-the-stump green wood, since I started gassifying 4 years ago. After it gets up to temperature (2000 degrees) it burns all of the secondary wood gasses and gets heat from them. Mostly water vapor and co2 left to go up the chimney. Definitely not for everyone, and probably not even for me when I get older, but for now it works.