firefighterjake said:...I usually agree with you Rick . . . but I have to say my outside exterior stainless steel chimney may perhaps lose some heat, but the Oslo is heating my 1,800 square foot house fine . . . there is very little creosote . . . and as for ease of cleaning . . . it's a pretty simple process to go outside, remove three screws on the cap, run the brush up and then reattach the cap . . . typically I can do this in 10-15 minutes . . . and clean up is pretty simple . . . I only put away my brush and tools and go inside to wash my hand since the little bit of creosote is now on the ground.
No question that there are multiple perfectly acceptable, safe, and effective ways to install a woodstove. Each installation is somewhat unique, and must be tailored to the structure, the code/mfr's requirements, and the desires of the homeowner. I certainly didn't mean to imply that there was anything inherently "wrong" with going out and up with an exterior flue...I know full well that it works perfectly fine for lots and lots of burners. Rick
ETA: The OP's original question about the external flue had to do specifically with whether or not it would decrease the probability of a chimney fire spreading into the structure. Well, if you're planning on having a chimney fire, I'd say that having the flue as far away from the structure as possible is a pretty good idea. Actually, if you're planning on having a chimney fire, you might just want to heat your house with something other than a solid fuel-burning appliance. Regardless of the flue configuration, I think chimney fires are relatively easy to prevent. Said it all before...proper installation, seasoned fuel, thoughtful operation, regular inspection, maintenance, cleaning. A lot of factors need to be considered in the selection and installation of a woodstove, and in most cases overall cost is an important one. If the structure offers the homeowner the choice between going up inside with single or double wall stovepipe, then out the top with Class A to daylight, or out the wall and all the way to daylight up with Class A, choice number one will invariably cost less. That might be an important consideration in some cases.