Trying to figure out if a liner is required to be run up the entire length. The pellet stove is in the basement and from where it is to the top of the chimney is 28 feet. It is a large brick chimney with the clay 10" liner that is in good shape. I took out the wood stove that was down stairs and i have 18 feet of three inch flex liner to install into the excisting chimney. My question is do you have to install the liner all the way to the top cap? What would be the negative affects of not taking the liner all the way up to the top?