A real newbie here, I am sure that during my whole life I burned no more then 10 logs of wood, LOL. Last wee I had a contractor in my house to estimate cost of installing Hearthstone Clydesdale fireplace insert. It turned out that my chimney already has clay liner, roughly 7"x7", square. Also I've been told that MA building code requires full length _CLAY_ or SS liner and my setup allows me to chose between relining full length ( 25' ) with SS or do a partial setup. Most of posts/articles that I've seen were "SS liner versus no liner at all" like this one (http://www.safesidechimney.com/woodstoveold.htm). I'm buying into that part, I need a liner, but how to determine whether I need to reline existing clay liner? The existing one is pretty close to specs in terms of size. Another argument for relining would be much easier to do a sweep, with partial install I imagine I'd have to slide the insert out to do it properly, is it true? Some info about my setup: - 40 years old house; - chimney is inside the house; - insert goes into existing fireplace that doesn't look like it has been used a lot; Later in my conversation with dealer (the guy in this business for more then 20 years) he said a very strange thing, he cautioned me not to reline to prevent OVERDRAFT which can lover efficiency of the insert, he said it is mostly applicable to inserts because you do not have a dumper in this setup. I would love to hear comments on this statement too.