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Is it possible to insulate an exterior wall masonry chimney with Roxul?

I'm considering buying a small house which has an exterior masonry chimney. Would it be possible to insulate the chimney from the exterior with Roxul to reduce the tremendous thermal bridging through the uninsulated stone? I'm not particularly worried about the aesthetic downsides.

Asked by Elliot Firestone
Posted Jun 7, 2014 12:05 AM ET


2 Answers

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There are several potential problems with this type of work. The problems relate to fire safety and code issues. For more information, see Providing Outdoor Combustion Air for a Wood Stove. I suggest that you not only read the article, but also read Dana Dorsett's comments and the resulting dialogue.

Answered by Martin Holladay, GBA Advisor
Posted Jun 7, 2014 6:44 AM ET


Thank you, that is almost exactly the discussion I was fruitlessly searching for! Exactly the sort of extremely valuable information that makes me an avid reader of this site.

I neglected to mention that the chimney currently contains a gas fireplace insert. I assume that a gas fireplace with an insulated vent would not raise concerns over the temperature of surrounding wood or require a combustion air supply in the same way a woodstove does. I would be considering a sealed combustion gas fireplace for efficiency and lack of depressurization, but would want the assembly around the chimney to be safe for future homeowners who might use a different fireplace insert.

Thanks again for pointing me to the right place!

Answered by Elliot Firestone
Posted Jun 7, 2014 10:57 AM ET

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