Closing Up Unused Chimney

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Old 01-04-15, 11:03 AM
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Closing Up Unused Chimney

I have a fireplace in my basement that is an eyesore, and is not used. I want to simply drywall over the entire fireplace and close up the chimney. I have read some competing suggestions as to how to do this. Some say that I should simply cap off the flue on the roof with a piece of sheet metal siliconed to the top and then placing some insulation in at the bottom in the fireplace. Others seem to suggest that I need some kind of airflow to continue through the chimney to prevent condensation issues.

Can anyone advise as to the best way to handle this?
 
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Old 01-04-15, 05:35 PM
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I'd use something a lot more substantial than just silicone to fasten the cap in place. I'd probably use a minimum of 12 gauge steel, painted (or better, galvanized) to reduce rusting, bent to fit over the chimney and help in place with a couple of Tapcon screws.
 
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Old 01-05-15, 11:33 AM
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Any need to keep some sort of airflow through the chimney, or can I just close off the top and add some insulation at the bottom?
 
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Old 01-05-15, 04:03 PM
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No need to have airflow through an unused chimney. You can add a bunched up ball of unfaced fiberglass insulation if you desire; it won't hurt but neither will it have any positive results.

I would probably frame around the existing fireplace in a manner that would allow a future owner to resurrect the fireplace. I don't particularly like fireplaces for several reasons but a majority of people DO like them. Being able to put one back in service at a later date may be a selling factor.

OR, if you are absolutely sure you don't want it and don't care about any future owner you could stuff a ball of rags, insulation or whatever in the flue at the top of the chimney down about two to four inches and then add concrete or mortar to completely seal the flue.
 
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Old 04-03-16, 08:35 PM
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Wow, I can't believe I asked this a year ago - I got to work on installing a bathroom in this basement and neglected the fireplace. I have framed a stud wall in front of the fireplace and will simply go with drywalling right over the existing fireplace. This will leave the fireplace to be used if some future owner desires.

I wont bother with insulation as it has no benefits - do I need to cap the flue even then? It almost seems like there is nothing I need to do? I just want to check again now that I am working on this project now.
 
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Old 04-04-16, 12:18 AM
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I think a removable cap is wise to keep out the rain and any critters that might otherwise enter. Heavy sheet metal bent to fit and secured by tapcons on the side to allow removal at some future date. I wouldn't go crazy trying to make it an airtight seal.

OR, you could install a top damper that has the control cable down to the fireplace. Then the only work necessary to re-use the fireplace is at the fireplace itself.

One brand, picked at random from a Google search but similar to the one I installed at my previous house. Seal Tight Chimney Top Damper | WoodlandDirect.com: Chimney Top Dampers & Accessories, Sealtight
 
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Old 04-04-16, 02:08 PM
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Could I bother you one more time to ask why adding insulation at the bottom to the fireplace, will not add any benefits?
 
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Old 04-04-16, 02:56 PM
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You're not bothering me, I do this to avoid doing what I really should be doing.

What benefit do you think adding insulation would give? I can't see it hurting anything but neither can I see any particular benefit. Now if you mean adding some insulation behind the wall you have proposed in front of the fireplace, then yes and I would use a rigid batt such as Roxul.
 
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Old 04-04-16, 03:08 PM
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Thanks again.

I guess what I mean is would the addition of some insulation in the fireplace at the bottom not at least cut off the draft that would come in through the chimney?
 
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