Old Chimney, New Gas Fireplace

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New Member
Feb 7, 2023
Washington, DC
Hi all! I just got a (very high!) estimate for my chimney project, and I'm trying to figure out if there's an easier way to accomplish the same goal, which is a working, vented gas fireplace. Context: I live in an old rowhouse with an original chimney on an interior wall that was at one point wood-burning. At some point, the previous owner installed a ventless gas fireplace insert (which sets off my carbon monoxide detector every time it gets turned on and has pretty fake looking blue flames). The interior of the chimney and firebox haven't been kept up, but I have no reason to think they're in particularly bad shape. The chimney above the roofline did get dismantled and capped with roofing material (photo attached).

I would like to replace the ventless insert with a vented system, and figured that I could use install some kind of vent pipe in the pre-existing chimney and that would be pretty easy and not wildly expensive. (Like a B-Vent?) But the first chimney company I spoke with told me that I needed to rebuild the entire chimney from firebox to flue cap - to the tune of $22,000.

Can this really be my only option?! I feel like I must be missing something.

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The chimney needs to be inspected before it can be used for any type of venting. It needs to be verified as safe for use. Unless you have the ability to vent a gas unit in another location, this inspection is a must.
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Thank you so much for your reply! And absolutely - safety first! But since taking the roofing material off to have the chimney inspected is a bit of a production, I'm trying to get a general sense of the project's cost before doing that. (Although maybe that just isn't possible.)
Have you even tried to get the vent free unit serviced. Maybe at least get a tech. out to check the CO with a meter to give a good baseline where it is? That 22k might be a couple of hundred dollar service call to take care of the issue. Possibly a new set of vent free logs. I still agree with a chimney inspection at the least though. Technically, most vent free logs say that if installed in a vented appliance the damper should still be open. At least most of the manuals I read say that.
I believe the install manual for the vent free set will tell you the fireplace must be fully functional to even install them into the fireplace. So the stack should be safe and complete.