How to thermally insulate above a chimney insert

[sophiedog]

I installed (myself) a small Drolet (non-cat)wood insert into my equally small early '70s hearth. Also, an insulation wrapped 15 foot round, flexible, stainless steel liner was installed from the top of the chimney to the insert. The metal damper plate has always been missing and I am wondering how to thermally insulate around the liner just above the insert so that I don't lose a lot of room heat and don't set the place on fire.
Are rockwool boards the answer along with some kind of caulk or spray?

 

[EbS-P]

I stuffed Rockwool up in the smoke chamber as much as I could then made a blockoff plate to seal the damper area and added another couple pieces ontop of the block off plate.

 

[sophiedog]

Hi Ebs-P, thank you for responding . What did you use to make the block off plate? I have looking around and thinking of using a ceramic blanket material like Kaowool that I can buy through Amazon to stuff up the chamber ( higher temp rating but more expensive) rather than Rockwool

 

[sophiedog]

Ebs-P : dumb question I just asked about the blockoff plate. A little research and I see what a fireplace blockoff plate is and that its made of metal fabrcated on site. "now I see" said the blind man.

 

[EbS-P]

Ebs-P : dumb question I just asked about the blockoff plate. A little research and I see what a fireplace blockoff plate is and that its made of metal fabrcated on site. "now I see" said the blind man.

It’s easier to do before the insert goes in but with a cardboard template one can do a good job. I thought heavy gauge would be better but I was wrong.