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.

 

[Slimdusty]

Liner reinstalled, block off plate back in place and sealed around the edges. Glad to be done with that!

 

[EatenByLimestone]

Excellent!

 

[Slimdusty]

Flu probe installed and insert back in place. Only thing left to do is put some stove cement at the adapter. That will get done when I have my first fire of the season, which is going to be awhile. Will update this thread during the burn season in case anyone is on the fence with doing something similar. I hope to see a noticeable gain from my improvements.

 

[Slimdusty]

Update - observations and questions.
So I have had a few overnight fires to take the chill off. My draft is noticeably stronger due to the insulated liner. When they say the flu is the engine of the stove, that is easy for me to realize now. As far as my insulation job behind my insert that sits on exterior wall, too early to notice any difference as we need colder temps for an extended period. I have my flu probe close to the top of the insert, about 6”, so I realize I will see higher temps than some of you other. I do question at what temp I should start shutting down my stove on reloads? Still learning but I am finding it hard to keep the temps below 800 peak temps after a reload. That tells me alot of wasted btu’s up the stack, no? Also, when after a reload, I can shut the air down much much sooner than last year with uninsulated liner. However, if I shut the air down like I think I should to slow the burn down, I end up with sooted glass on the lower half of my glass. Secondaries are very robust and keep the top half clean and flu temps high but the lower glass gets dirty. Suggestions please