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.

Make sure you neutralize the pressure in the room its in by opening a window, if you dont have a pressure problem in the house you may need to extend the chimney. You are on the very cusp of the manufactures minimum rating and you have that longer then average offset..I think thats most of the problem. You extend the chimney buy using a anchor plate and a transition plate. The transition plate would be optional if you have a good way to attach the anchor plate to the current liner. Normally it would be installed like this: Transition plate covers the chimney and the flange for connectiong the liner points down the chimney The anchor plate bolts to the top of the transition plate and provides a connection for the class A chimney,. If it wouldnt look too rediculious i would add 4 more feet. If you have a negative pressure problem in the home, (if cracking the window improved things dramaticly) then you have a complete other set of problems to deal with. go to www.duravent.com and look up the three parts. You will need the transition plate, the anchor plate, and what ever length of pipe you need. This is a whole nother can of worms, but the stove might perform worse in the basement. There are absoluty no guarentees that your basement will provide a better installation then what you currently have. To make a long story short, your house is one large chimney, heat rises in the attic positivly pressurizing the attic, the main level of the home is is a pass through point, and is typically neutral, and the basement is the supply, wich is under pressure because there isnt much air that can get in the basement, making it negative for pressure. That means the new chimney that is way up in the air has a pretty postive pressure at the top, and the stove at the bottem is in a negative room, and becomes the appliance that tries to neutralize the basement. The stove could be thought of as the same effect of opening a window to neautrlize a room. You can imagine the potential draft problems...

This year I purchased my third insert in the past 12 months, so I've done a fair amount of investigation and shopping recently. I put one in the house that I sold and two in the house that I just bought. The main difference between an insert and a simple wood stove is the fan that an insert utilizes. Circulating the hot air into the living space is a huge efficiency advantage over just having a hot stove radiating heat. Believe it or not, the price between a good insert and stove is about the same. Of course, you can pay a little more for the blower and trim kits for the inserts, but it's not a huge difference. Try to get the dealer to include them in the deal and don't let him "nickle and dime" you on those items or the installation. Shop around and be sure to ask if the price that you are getting includes those things. The other issue is that an insert in your fireplace looks more "finished" sitting in the opening as opposed to the wood stove. If you have a standard masonary fireplace, chances are a wood stove would not fit inside the fireplace itself. Then you have the stove sitting out in the room and the fireplace opening left to deal with. My wife wouldn't go for that in her living room! And guests have commented on how nice the big glass doors make the fireplace look. There is a lot of info on the internet so do your homework and shop around.

Wood stoves do burn clean. Yes, they emit CO2, but it's the same amount of CO2 the tree would emit as it decays in the woods. Once the fire is going and the stove is functioning, you can go outside and see nothing coming from the chimney as the new stoves have "clean burn" technology which has smoke reenter the burn chamber, as smoke is unburned gas that would normally go up the chimney. The old stoves were just fire boxes with ways to limit the air to the fire. So when the owner closed off the air, all the fire did was smolder, which caused smoke. Hence the name given them today, "Smoke Dragons". When you look into a stove or insert, bigger is not better! These are appliances and must be sized to the area you plan to heat. Let's say you have a 2,000 SF home. You don't necessarily want a unit that will heat the entire home to 70 degrees, as the bedrooms should be cooler, etc. So do some research before going forward.