Hey everyone. I have a jotul 450 kennebec. First off, its a great insert, puts out awesome heat. I have 2 year old seasoned oak and walnut. Its been split and stacked for at least a year. The only things IM suprised about is the amount of ash buildup i get. Once I get good coal buildup and it running smooth I cut the air back to one half. I can get the temps up to around 700-800 temps before cutting it back. Anyways I have been taking about 3 gallons of ash per 24 hr usage. I have been burning alot of walnut lately. Im wondering if that 's what the deal is. It seems when I burn white or red oak I dont have as much buildup. It burns great and starts fires easily. I do have chunks of uncombustible charcoal mixed with my powdery coal. In the morning I have been taking all the good orange coals and raking them to the side so I can scoop the powdery coals out. The way the 450's firebox is designed, its stepped off and slanted down, and once the coal is level with the door it can get messy. So is this a walnut problem, or should the wood be seasoned another year or so. In general Im happy with the unit.