I just cleaned my chimney today, as I do once per year, every year. It's an uninsulated, exterior, masonry chimney, so it's pretty much designed to condense gunk on it. Well, after the first year of operation of the new Oslo, this is the least amount of creosote I've ever had by far. 3.5 cords of wood, and only about a cup of loose powder. As I climbed the ladder, I could see that the mesh on the chimney cap was clean and shiny. This is the most wood we've ever burned in a year (heated the house closer to 100% with wood, compared to other years), and still made the least crud in the process. Nice!