Block off plate option....

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matlocc

Member
Jan 22, 2015
28
michigan
I have an insert with a pipe running up the existing chimney. The clearance to attach the pipe is very small. I currently have run it for 2 seasons without a block off plate.
My pipe terminates at thetop of the old chimney. There is no plate around it,just over the top.
Will putting a block off plate at the top help? I can't really get back in to put one on just above the insert.
 

begreen

Mooderator
Staff member
Nov 18, 2005
94,654
South Puget Sound, WA
Is this an exterior chimney? If so, yes, a block-off plate can make a notable improvement in heat output. If there is space behind the insert then adding a layer of roxul insulation behind it will also help. The insert would need to be temporarily removed in order to install the block off plate.

Is there a cap over the flue exit at the top of the chimney? What is supporting the liner up there?
 

matlocc

Member
Jan 22, 2015
28
michigan
It is a clay chimmney liner, the pipe is just held in the center by wires in an x shape. Just a square cap over the chimmney top. I can see down to the insert from the top. It is only 13 ft tall.
 

matlocc

Member
Jan 22, 2015
28
michigan
The pipe is held in the center by a wire x. There is a square cap over it. I can see down to the insert(with a light) It is only 13ft chimmney. I also have a surround cover around the insert.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
29,218
central pa
The pipe is held in the center by a wire x. There is a square cap over it. I can see down to the insert(with a light) It is only 13ft chimmney. I also have a surround cover around the insert.
You are wasting a large ammout of heat up and out the chimney around the pipe. You want a plate top and bottom. And insulation around the pipe and ontop of the bottom plate
 

EbS-P

Minister of Fire
Jan 19, 2019
3,038
SE North Carolina
Yes you want a well sealed and insulated if possible (don’t use fiberglass it’s not allowed use mineral wool) The difference in the frost melt on the roof(it doesn’t snow where I’m from) is very noticeable and the temp of the wall behind the chimney(interior chimney. Was 15 degrees cooler at the ceiling. All that heat was radiating in to the attic too.