A fireplace "insert" is intended to fit into a pre-existing masonry fireplace. I assume you mean a metal factory built "zero clearance" wood burning fireplace for new construction The wood burning fireplace "duct" you mention is a chimney whether it is masonry or metal. You can add gas to the firebox or put a gas log kit in it but the chimney must still be designed for a wood burning fireplace and sized for the fire box opening (unless you want to pay for it to be tested by UL). You need to either try harder to get the chimney offsets to work or use a metal factory built gas fireplace already tested by UL with a B-vent through the roof. Factory built gas fireplaces are made in two types: Direct vent and B-vent. The Direct Vent unit has a double-walled metal vent pipe that can terminate on an outside wall or through the roof. It is a closed system so the fireplace gets combustion air from outside through the outer wall of the vent and the firebox has a fixed glass enclosures. The B-vent unit has a single-walled vent that can only terminate through the roof. The fireplace takes combustion air from the room so it can be open to the room. Many of the units have folding glass doors. Carefully read the instruction for installing the vent. Consider an optional outside air supply duct to the firebox.

We are also trying to decide between gas insert options, or maybe put in gas logs and doors. The fireplace already has a gas starter, and there is an outlet next to the fireplace (but obviously not in the firebox), so I'm not sure how hard wiring would be. We've looked at Mendota, but have serious sticker shock and don't think we need that much heat (it's primarily for ambiance and to take the chill off on cold evenings). Heat&Glo was recommended by a local dealer, but we haven't seen one in person yet. Lisa, which direction did you go and have you been happy? Mom2SF, are you still happy with your choice after a couple years? Thanks!

qtpi: This is likely to be quite involved and expensive. On the plus side, you apparently already have a chimney designed for solid fuels. Building a wood burning masonry fireplace is a highly skilled art but could no doubt be done utilizing the existing chimney. Keep in mind such a fireplace is extremely heavy and would require a subfloor foundation. A prefab metal fireplace might therefore be much easier. As far as the wood or gas option, I'm not sure this is possible or legal. If it were me, about the last thing I'd want in a place where I'm burning wood is an outlet for flammable gas. Also keep in mind your present wood stove is a far more efficient heater than any fireplace you could build.

That is a really nice set Rebbecamom. I think your concern was wixe because, from the photos, it looks like the cabinets projecting at the side of the fireplace may cross the zone where you shouldn't have combustibles with a wood fire. At least for our wood burning fireplace, the installation instructions say there should be no combustibles in front of a line that goes out from the side of the firebox at 45 degrees for 24" on each side of the fireplace up to some height above the fireplace. I don't know how universal that requirement is, so perhaps your set up would have been okay with your fireplace. We put in a wood burning fireplace for the family room that is sealed so there is no issue with embers or sparks. It heats the family room really well and provides the look of real flames, but one can't hear the crackling of the fire. Also, we don't feel comfortable running it when our little grandchildren are visiting because the glass gets really hot - if we were going to run it with small children around, we would probably want to put a protective fence of some sort around it which would not help ambiance. It uses external air intake which can be adjusted to control how hot the fire burns and to damp down the rate of burn. It is nice to not have to worry about leaving the fire going when we go to bed. For the living room fireplace, we are considering putting in a gas log set - we have never used that fireplace and have no need of running it for heat, but it would be nice to turn it on occasionally for looks when using the room. We don't need two heating fireplaces and I don't want to deal with wood in the living room.