Replacing A Gas Zero Clearance Fireplace with Pellet or Wood

I have a majestic ZC fireplace in my 14x22 family room that has 18' ceilings. it's flush to the middle of the 14' wall and there is a bump out 2'x5-6' x about 30' tall full chimney chase that houses gas b-vent for both the ZC and my gas furnace. It has a matching mantel with what looks like granite glued to front of unit and on floor (wood for the rest). Its pretty.. but is USELESS from a heating standpoint and it uses lots of gas with a pilot light that is bigger than my smallest stove burner!

I have been dying for years to get a pellet or wood burning stove in its place. I figure pellet might be the easiest from a chimney standpoint. I want to either use the existing chase or direct vent a pellet with a slight vertical rise. I dont want a full wood stove chimney bolted on outside of chase. So this is as challenging project, but I can't be the first person to have this issue. I started to remove the ZC a few years ago, but got too busy so stopped at just some trim removal an frustration over the granite heavy glued to the front of the unit.

This leads to some ongoing questions. Is there a legal way to line B-vent to work with pellet so that I have no exposed new pipes? What units and mfg would work well for my requirements? my house is 2600 sq foot..but I am realistic and can live with first floor and great room equivalent of about 1500 sq ft.

Any and all comments and advice are welcomed. I have not started the rip out yet.

It's definitely ZC gas into b-vent I agree that rip out gives best options. I considered the alcove, but the top clearance might have the opening higher than I would like. I did find 3 insert type units that would work there: a kozi, an enviro and a rika. Went to local stove store to see if they had done this type of retrofit before and they did a few last year. They like to try to save the front granite in place which means the stove behind it is cut out in pieces to which I chuckled, but not sure what the resale market is for a zc gas unit that gives off zippo for heat. I have them coming next week to look at the space and give a proposal. Talk is cheap.

The rika integra II was running at the store. That is some stove. Built solid and gives off lots of heat, but pricey at $5K. The other 2 units are in the $3K range, will do the job, but are not the stove the rika is. Dealer said he could reuse the gas b-vent in place. I said, my research said no as it will handle the heat, but the cooling at the upper end of the 30 foot chase could corrode the pipe. I would love to do that as I have a neighbor 20 feet away and did not want to blow exhaust gases on them. But I think I am settling on a direct vent with a vertical rise. Location will meet NFPA if centered in the chase.

I chatted with my insurance agent for a spell and never did get a clear answer on the potential increase for pellet. Last I investigated pellet was not as hazardous as wood burning and was more peer to the zc gas I have now so no additional premium was required.

Ok I have an update. ZC gas unit has been removed. It took about 3 hours total and that includes removal granite slaps and mantel surround, plus reassembly of fireplace once removed (doors, logs...etc). There was minimal damage, all recoverable, to surrounding sheet rock where granite panels were glued. Mantel surround was not holding by much other than its legs and a caulk beed at top. Nails shot into it where not hitting any wood behind the sheetrock. A section of b-vent (lower 5 feet thankfullly) was not properly twist locked and dropped on removal. That has been fixed, capped and a brace placed under it so nothing can move. The outside air intake was not properly sealed to the unit. The wall outlet for that has been capped for the time being.

I am leaning towards the Quadrafire Mt Veron AE Insert or Free standing. Both will fit and meet proper clearances to combustibles and can be vented out the back. I am going to prep the area and let the dealer do the stove install most likely. But this does lead to some questions.

For insert: I left the granite in front of the fireplace glued to floor. It will meet the needed 6" in front clearance to combustibles. However, nowhere in the manual does it specify any clearances or materials needed under the back 2/3 of the unit. I'll run same question by the dealer. I have 1.5 inches to fill above the OSB chase floor to meet the level of granite (granite and hardwood floor make that 1.5 " total). What material should I use? Also since the insert is 400+ pounds...with maybe 5" service clearance on each side when I am done, how the heck do you get behind it for service or to hook up L-vent and air intake? Next question for insert. Insert space is just studs and insulation and b-vent from furnace, but i really want to cover it and put a top roof on it to cut air infiltration. (first firestop is to almost first floor level 8' up) What material should I use? Durarock? Fireproof Sheet rock? Mind you all required clearances will be met with .5 inch of combustible material over the studs, but the back of the unit must give off some heat and I just want to add extra safety?

And FYI, since I have no bends you could easily "sleeve" the straight b-vent with L-vent provided that you went outside to top of chminey and secured the L-vent in center of b-vent About 35' in the air so not my first choice! Although I do worry about our homes being about 22' or so apart and the downhill neighbor complaining about the direct vent smoke on start or any smells from burning. So I have options to raise outside flue up a tad or worst case sleeve the B-vent.

That's it for now... I will be proceeding slowly and leaving options open.... won't order specific stove until I get the area prepped. All thoughts and guidance are welcomed!!

There already is a "false ceiling" made of OSB at the ceiling height level inside the chase. Both b-vents passthru in in square holes with a sheet metal device that is designed to keep the pipe an inch or so away from the OSB. There is no insulation above or below the OSB and no caulk seal. The active b-vent for the furnace does get pretty warm to the touch when the furnace is on. NFPA 211 says b-vent can have combustibles no closer than one inch, but my real question is: Should I box this active b-vent in leaving the one inch needed or just leave it as is? Also where the b-vents pass true the sheet metal spacer at the false ceiling, should I use hitemp sealant there? Do I need to add insulation to the false ceiling? (would need to be some sort of rigid board insulation as I can't really get above it at this point.

I am definitely trying to avoid the drafts of the old setup. I will either sandwich the existing false ceiling from below with insulation or even place a second false ceiling lower in the chase. Is the removing the mantel and placing fireproofing board under its location really necessary or just personal choice safety or stove design dependent or required by local code? The Mt. Vernon manual does not indicate the need. The real question is , how much heat does the Mt. Vernon give off in the section that sits behind the living space sheet rock wall ? My wood mantel is removed and I had planned on putting it back. The lower end of the mantel at the shelf would only need to be modified on the bottom if I went with an alcove and full stove to meet the needed 43" alcove height. That would actually be a tad high since some of the stove would be sitting in front of the alcove.

I would feel better about sleeving the B-vent with L-vent on straight runs (which mine is) if they made adapters that would insure the l-vent was centered in the b-vent for the entire run. This should give you at least another consistent 1" air gap between the 2 pipes. Theoretically this should be fine. But yes it should be tested and covered by NFPA 211. The codes and methods are slow to evolve especially in the pellet stove l-vent retrofit design area. Hence conversations, all good, like this one.

On the project front... I am still looking at my opening and designing in my head. Once you gut the ZC gas unit, the design possibilities are endless. Including making shelves where the fireplace was for the flat screen TV that will go above it! Makes wiring and theater speaker placement easy. The pellet stove would then go in the corner to the left where the TV is now. This option leaves the chase to living space properly sealed and not leaking air with little or no access to seal it up. It also makes the stove install easier, faster, cheaper and gives you good access to maintain and keep the openings at air intake and flue sealed properly. Still thinking out loud here. I am going to box in the furnace b-vent (with proper clearances.. as it does get warm to hot touch), put in new lower false ceiling sheet rock and seal entire area. Have to decide on and raise chase floor 1.5 inches. All of this has to be done no matter what direction I go.

Looks like I found a winter project. Question is: when the heck will I be burning pellets??