Block-off plate at top of flue liner??

[Mattziv]

Hi, first poster here, I have been lurking for sometime, trying to learn what I can from previous discussions.

I have an older insert, it says "The Blaser" on the front. Rectangular solid door on front that can be swapped for a screen. It seems ok, but I don't have enough insert experience to compare. I'm sure something modern would kick its butt.

It sits just outside a very old Heatilator that is no longer 2 separate chambers because of the way it was cut to fit an insert liner.

When I recently had a liner sweeping done, he said I should close off the top of the chimney with a block-off plate caulked down, with non backed pink insulation stuffed underneath, this would surround the insert right below the cap.

Research has lead to only block-off plates at the bottom of the liner. Also the type of insulation that people use in there is Roxul, not the pink stuff.

Basically, is he right? Because I am not seeing any information about that top block-off modification.

I feel like a block-off on top or bottom would really make this better than it is.

At this point "The Blaser" is separated from the original Heatilator firebox by a thin galvanized plate. Everything else including the Heatilator's firebox, circulation vents and outer heat chamber all the way up are exposed to the outside. Not very efficient!

Thanks for listening!

Matt

 

[dafattkidd]

Hey welcome to the forum. It seems like the chimney sweep used the wrong term or you misunderstood his description. You've come to right place. So there is something called a top plate that looks like this. It is caulked to the top of a clay liner, connects to a stainless steel liner that runs inside the clay liner and connects to the insert, then a cap is placed over the top plate.

 

[dafattkidd]

Can you explain your chimney set up a little more so we have a better idea of what you mean by liner? When you say liner are you referring to a clay (terra-cotta) liner or a stainless steel liner? Do you have a chimney cap of some sort? What exactly is exposed? Maybe post some pics. That would be super helpful.

 

[begreen]

He is in error, fiberglass should not be used, Roxul or mineral wool has a higher temp rating. A top cap is proper if there is a full stainless liner running down to the stove.

 

[Mattziv]

Can you explain your chimney set up a little more so we have a better idea of what you mean by liner? When you say liner are you referring to a clay (terra-cotta) liner or a stainless steel liner? Do you have a chimney cap of some sort? What exactly is exposed? Maybe post some pics. That would be super helpful.

I guess I was referring to both. The insert has a metal tube liner that goes up the original clay liner. The metal tube liner terminates at a metal chimney cap. The original clay liner is exposed from the top down to the old Heatilator fire box and its outer layer heat chamber (which is exposed now because it was cut into)and its connected heat chamber circulation vents.

 

[Mattziv]

He is in error, fiberglass should not be used, Roxul or mineral wool has a higher temp rating. A top cap is proper if there is a full stainless liner running down to the stove.

That's what I thought, I'll have to get something that will stay up there if I go the top block off route. From what I recall Roxul crumbles like bread. There is at least a cap on the steel liner.

 

[kevreh]

For my insert I have a top plate, like the one in the picture, caulked in place (special heat rated caulking). I also put roxul around the liner where it goes into the chimney. I did a feel-test and there's no air movement in the fireplace cavity. Is there any benefit, beyond minimal, to adding a block off plate as well?