HOW TO INSULATE WALL THIMBLE BETWEEN CONCRET BLOCK

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Jabbers

Member
Hearth Supporter
Oct 15, 2008
98
NE OHIO
I was wondering what insulation to use in the open cavity between my thimble. I could tell last winter that cold air was getting in from there. Any suggestions?
 
My vent kit had a white fiberglass-type insulation with a aluminized barrier on one side. This stuff should be available at a good stove dealer.
 
How big a gap are we talking? Are you talking about the gap in your CAK? I used high temp silicone; yes, I know I probably didn't need to do that. I also wrapped the CAK tubing in duct insulation and finished with Frost King tape.

Hope that helps
 
Depending on your situation and the size of the opening or gap you are trying to insulate. Here are some ideas that I did for my thimble:

1. I took some flashing metal and created a secondary outer shield and ran the thimble sleve through it.
2. Then I used "Fire Block" spray insulation to seal the openings and gaps.
 
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