Insulation to plug flue after liner install

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Borgia

Member
Jan 14, 2016
7
Patterson, ny
Recently I installed an insulated 6 inch chimney liner in my flue. There is still a lot of room around the liner in the flue that heat would escape up. I was thinking of plugging the room in the flue around the liner with rockwool insulation. Is this safe? Recommended? If not what would be alternatives? The insulation would be about 18 inches above wood stove insert and directly touch the liner
 
Search this forum under “block off plate”. Basically it’s sheet metal fit to the opening you’re describing. Rockwool insulation sits above the sheet metal. Rockwool is safe for that application. You will get better insulating quality from this than the Rockwool alone. That, and you won’t have to deal with the bits of Rockwool dust that will shed over time.
 
Info on making a block-off plate is also here: