Toby Duebber

Well, my basement is a Berm from the 70's, (built into the side of the hill, with one side open), and it's made of some very thick concrete. About fifteen or twenty feet up is an overhanging deck, and it would be a big pain in the neck to go through it. so i thought maybe a heat sink would allow us to stop at just below deck level.

This might be a dumb question, so bear with me.

My family is considering putting a pellet stove in our basement, but due to how it's constructed the standard chimney would be rather expensive and it would have to go through a deck. That's not exactly ideal.
So i was thinking about alternative ideas, and heat sinks crossed my mind. Would it be possible to put a large heat sink such as a big block of copper or whatever somewhere in the chimney assembly so the chimney can be shorter than it usually has to be?
Or is that just stupid?