Question: Great site at HearthNet! I've got a couple of questions on a Gas Fireplace installation we're planning. We want to put in a gas fireplace in our living room (it's a small room and we want to minimize the space the fireplace unit and it's corresponding chase will take up-so depth is an important consideration), it will replace an existing wood stove that is being vented out through our chimney. There is no fire box cut into the chimney at all (the chimney is not wide enough to accommodate a fire box, so the current wood stove is free-standing with piping connecting it to the flu (8 inch flu). We're looking at the direct vent Gas Fireplace models (we'd want to go with a top venting model so we can position the fireplace right up against the inside chimney wall to save space). <p> I've heard dissenting opinions on doing this, but is it possible utilize the current flu (that had been used by the wood stove) with a Direct Top vent Gas fireplace?-I've heard from my local dealers both, 'yes it's no problem' and 'no it's just not possible w/ direct vent to use an existing chimney flue, instead use a much less efficient B-Vent Gas model', or if that's not confusing enough I've also heard-'maybe' on direct vent in the chimney as long as the chimney is re-lined -but that may cause it to have too small a diameter for the tubing.....???? Can you comment on these opinions? <p>Any clarification would be great on these 'expert' opinions. Answer: You pretty much got it: 1. Use a b-vent which needs one 4" pipe up the chimney 2. Use a direct vent top vent which can take the 6 5/8 OD piping and line the existing chimney with it. 3. Some direct vents (mendota) use two pieces of 3" flex aluminum, which can be used to line the chimney. With any direct vent, check the manual BEFORE you buy, as there are limitations to the height and turns of these pipe runs.