Liner insulation install

[Slimdusty]

Today I pulled my liner out of my masonry chimney and wrapped it with insulation. While I have everything opened up I will be adding insulation above my block off plate. Pics to follow and will report back through this burn season to see how noticeable my improvements are. First, a question. Inside my fireplace there is a gap on both sides, between the front brick and rear metal shield, currently stuffed with insulation. See pic. I would like to seal this area off and not have exposed insulation, even though its not visible when my insert is installed. Any ideas on best way to seal it off?

 

[stoveliker]

Is it too thick for silicone?

 

[Slimdusty]

It’s a pretty wide gap for silicone, 1 1/2” wide give or take.

 

[stoveliker]

Then I'd put a metal trim there. Screw it and seal with silicone.

 

[EatenByLimestone]

What type of insulation is it? If it’s non combustible, you can use it to back an application of silicone. Fiberglass insulation isn’t non combustible. Do you have any leftover insulation wrap from your liner? You can use pieces of that, or rock wool to plug the gap, then silicone over the top of it.

 

[Slimdusty]

What type of insulation is it? If it’s non combustible, you can use it to back an application of silicone. Fiberglass insulation isn’t non combustible. Do you have any leftover insulation wrap from your liner? You can use pieces of that, or rock wool to plug the gap, then silicone over the top of it.

It was old nasty fiberglass, so I took that stuff out and stuffed a lesser amount of rock wool into the gap. This actually decreased the gap to span with silicone so I think i will go that route. Will get some silicone this week.

 

[Slimdusty]

This fireplace is a “heatilator” style I believe, the back and sides are shielded in steel. When I installed my liner I needed to cut out a section of steel to facilitate the liner, see pics. This was several years ago. So today, as I am inspecting things I realized there is a large hollow cavity inside the opening I cut. Perfect opportunity to stuff a bunch of rock wool in the cavity, as this in on an exterior wall. I was able to insulate the back and sides pretty well through this opening.

 

[Slimdusty]

Newly insulated liner ready to go back in.