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keyser soze 03-02-2008 12:23 PM

New Ventless Gas logs in an old chimney. Now how to block the chimney?
I have a "real" fireplace and "real" chimney circa 1912. The chimney is in pretty bad shape so I had some ventless logs installed. Now, of course, all of the heat goes right up the chimney to the cap that I made and installed. I want to divert that heat out into the room but I'm not sure if I have the best plan or not.

My first thought is to put some sort of insulation up there (is fiberglass with no paper okay?) then make a sheet metal (aluminum?) piece that will go at the top of the FP opening to seal off the fireplace from the chimney. That should keep a lot of the heat off of the insulation. I was thinking something like JB weld to attach the new shield to the fireplace since it has some metal trim pieces up there. It can handle the heat but I'm not sure Liquid Nails or something similar can.

Is this a horrible idea? If so, what do other people do? Thanks a lot in advance all. :thumbsup:

Sammy 03-02-2008 03:45 PM

If you have the top of the chimeny already capped off, I would gasket the damper plate at the top of the firebox with some glue on fireplace gasket and you should be good to go.

Check for a cleanout door at the bottom of the fireplace leading to the outside. That may need sealing up also.

keyser soze 03-02-2008 05:13 PM

Thanks a lot for the response Sammy. :thumbsup:

The damper idea would be great if I had one. There is nothing but air between my new logs and the cap. There's a good sized pipe coming out of the bottom of the pedestal in the basement but it doesn't seem to be leaking anything from the fireplace. I guess my chimney was made before they started using dampers?

I'm going to the local stove and chimney shop tomorrow to ask about installing a damper. I can't think of any other way to seal it off correctly other than my sheet metal and insulation idea. Since I posted this I've been told that fiberglass insulation wouldn't be recommended for this purpose anyway.

Bummer. :censored:

AtlanticWBConst. 03-02-2008 05:37 PM

Roxul fire-proof insulation:

keyser soze 03-02-2008 06:07 PM

Very cool. Thanks a lot Atlantic. I'll track some of that down once I get the final plan worked out.

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