We just moved in to our new home in July. It has a old 80's era catalytic wood stove. I want to replace it with a pellet stove. The wood stove is piped with 10" chimney pipe. I'm pretty sure its single wall. Do I need to do double wall pipe all the way up through box at the top of the ceiling? I want to do it correct and safe. I have 17' cathedral ceilings in my great room. It would be $$ if I need to do double wall all the way but if that is the answer then I have to. There is a 10" to 8" reducer on top of the stove and I know Duravent sells 8" to 4" reducer. I was told I should use 4" pipe since our elevation here is 4500ft. Any advice would be greatly appreciated. Thank you, Todd