I'm not looking for a hyper efficient system. Just something that can help take the edge off the colder nights. The park I live in doesn't allow wood stoves but pellet stoves are fine. I want to be as safe and smart about it as possible. I intend on buying a 30 to 55g sized barrel. I have a few questions tho concerning the build. I currently have a pellet stove stove pipe system going through the wall. 3in pipe I believe. Does the exhaust pipe out have to be the same size as the pipe going in? The barrel I intend to stack brick around the inside walls. Does the exhaust going out of the stove need to be higher then the feed tube? I kinda want to build a 3in system for now and over the summer work on making a larger and more efficient system. Right now I dont need pretty, just functional. Any thoughts and ideas and plans are welcome. I eventually want to build my own heat riser with local clay as well. Sorry, 500 questions come to mind. I just want a design that works and go from there.