Q&A Sealing chimney to avoid heat loss

QandA Posted By QandA, Dec 1, 2007 at 6:16 PM

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  1. QandA

    New Member 2.
    Staff Member

    Nov 27, 2012

    I've installed a new wood stove into an existing masonry fireplace and am having problems with the amount of hot air escaping up the chimney. I have installed a plate in the chimney, but the chimney is pretty rough and it is hard to get a good seal. Will it help by running the pipe all the way to the top of the chimney and putting a correct chimney cap on, so only smoke/hot air from the flue can escape? It sounds sensible, but I just want to be sure before I spend the money.


    We usually install a fabricated sheetmetal plate on a level plane approx. 2 inches higher than the fireplace opening. We measure the area and cut the plate one inch larger on all sides. We notch the corners and bend the lip down. The ledge around the outside makes the plate fit tighter. You can use high-temperature silicone caulk to seal the plate to the chimney.

    This type of arrangement works very well whether running a 5 foot flexible tube up the chimney or relining the entire chimney.

    11/2007 Great article about making a blockoff plate.

    Link: Hearth.com article on block off plate fabrication
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