Hey Miles, a picture of the walkout basement area would help a lot, resized pictures down to the size of 45kb uploads to the internet quickly, it would help if you could indicate on your picture where you expect to place your
RMH & related chimney.
Without a picture, I might simply run the vertical length of chimney on the outside of the building, thereby avoiding any troubles caused by open doors or windows or whatever. I like the idea of your walkout basement location, supporting heat for the plumbing, and possibly support a large dry storage area for
firewood. Generally an outdoor or indoor straight vertical chimney that rises above the roof by 3' or so, will draft your RMH quite well, the idea is to capture as much heat within the mass, and then dump the remainder via the chimney. You might think about the flow of natural air currents over your roof, and as those currents wash along the roofline, avoid placing the chimney where the exhaust, washed from the chimney might flow into your doorway.
james beam