Added insulation to the liner and a block off plate...

I don't understand this too well. If the chimney is closed at the top why do you need a block off plate? If you install a block of plate and insulation you are wasting all the heat emitted by the SS liner. I can't see what energy you are saving around the insert because the cast iron box is inside a sheet metal shell that doesn't get hot once the fan cuts in. So, my question is, how does one "reclaim" the heat emitted by the liner?

I'm not so keen on being up on a second story roof...let alone wrestling with nearly 30 ft of liner while I'm up there. I watched the installer do it and was totally amazed - and very glad that I hired a professional. So I think I'll have to defer to the professionals for the insulation job too. And due to budgetary constraints, it'll probably have to wait until next year. I just hate having to re-do things. I'm all about doing it right the first time. So this will probably bug me for a while. :grrr: I just wish I had known to ask up front. Live and learn, I suppose.

I just took my 25ft liner out this weekend and insulated it, it was a tight fit before I insulated it and boy was it even more tight with the insulation. I got my insulation kit from http://www.chimneylinerinc.com/insulation_kits.htm and I bought a pulling cone as well. Without that pulling cone I would have been screwed with my install. I insulated mine due to draft issues, had smoke coming back into the house. Its not a hard install, you will need atleast 1 other person helping you. Check out this install video on youtube, it will let you know what your in for: http://www.youtube.com/watch?v=RRauuzjI-H4 .

That's my question too. I must admit i don't understand the physics here. Why adding insulation will improve the heating efficiency? To me, the liner gets heated because the heat/smoke emitted by the stove. so the heat will be emitted anyway,
without insulation, it will be partly emitted by the liner. With insulation, most of them will be out through the openning of the liner.

It's not like adding the insulation will reclaim the heat. But i do agree add insulation will increase safety.

Block-off plate is another story. I belive it will improve the heating efficiency. For an external chimney, adding insulation to improve heating efficiency doesn't make too much sense to me.

bokehman said:

I don't understand this too well. If the chimney is closed at the top why do you need a block off plate? If you install a block of plate and insulation you are wasting all the heat emitted by the SS liner. I can't see what energy you are saving around the insert because the cast iron box is inside a sheet metal shell that doesn't get hot once the fan cuts in. So, my question is, how does one "reclaim" the heat emitted by the liner?

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Mellow - thanks for the links, I'll take a look.

I too am still not sold on the physics of it all. I'd prefer the heat in the liner to be absorbed into the masonry chimney and radiate (however little that might be) back into the house. Right now, I seem to have really good draft and it hasn't been terribly cold, so I think that should improve as Winter rolls on. However, once Winter does kick in, without the insulation, I suppose there's more chance of the gases cooling as they rise through the liner and the potential for creosote increases.

On the other hand, with colder temps I should get even better draft which should mean hotter fires, which should mean less chance for creosote build-up, right?

Again, this is my first year with the insert. I'll see how things go and how the liner looks when it's time to be cleaned. If I'm happy with the insert's performance and there's no issue with creosote, I'll play it by ear and decide what to do at that point.

There's so much good info here and insights. I love this place!

Creosote buildup was another reason I insulated my liner. Uninsulated will always have more creosote due to being colder at the top, no matter how hot you run your stove it won't be able to keep a 25-30 ft liner warm at the top. Better draft and less creosote are the main reasons for insulation, well that and being safer if you have cracked tiles in your chimney.

My installer and I discussed this - my ~40 ft, 3-flue, center-of-the-house chimney has a stainless flex liner down the center flue for the wood stove. We opted not to insulate it, but in discussions, he was talking about a vermiculite product - kinda powdery, which would be brought up to the top of the chimney, he'd open up the top plate (whether it's sheetmetal, masonry, or a combo of the two up there I don't honestly recall), and pour it down in and around the liner to pack it in there. He estimated "about 12 bags of it" based on his experience. With the turn our chimney takes, I couldn't conceive of putting any kind of insulation sleeve around the liner - it was all he could do to feed the flex liner down the twisting flue. Are we talking about something completely out in left field??

Edit - attached a very old photo of the chimney, showing the twist it takes between the attic floor and the roof ridgeline - long before we insulated and finished the attic space. Yes it breaks thru the roof at a 45 to the ridge. Roofer LOVED flashing it. ;-P

Center of the house chimneys tend to stay warmer than an external chimney so sometimes its not worth insulating. Vermiculite is just another type of insulation that can be used, same principles involved.

For y'all trying to insulate the back of the fireplace.... If you have the room then maybe going with bricks is more cost efficient. I'm not sure because I dont have the room behind my insert. Here's a link to some ceramic bricks... http://cgi.ebay.com/2300-Degree-Pro...photoQQcmdZViewItemQQ_trksidZp1713.m153.l1262

I just ordered some blanket from this guy because he offers it by the foot and I only need 2 feet. What I think some people are forgetting when wondering about a blockoff plate is this.... Sure your chimney heats the space and it would be ok to retrieve some of that heat, but when you dont have the blockoff plate then you are constantly trying to heat the brick chimney. Hot air rises and so you are letting your hot air go up to the top of the chimney to be leached out by the bricks. You may from time to time get some heat back if you didn't have the plate, but most of the time your living space and insert top will be trying to heat the top of the brick chimney and succeeding.

drdoct said:

Hot air rises and so you are letting your hot air go up to the top of the chimney to be leached out by the bricks.

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I've got a vent further up the chimney chase that brings that hot air back into the living space.

Here's the ebay info.. Seller still has some up for sale..
Ceramic Fiber Blanket - 8# dens. - 1”x24”x25’ – 50sqft Item number: 300270992374
Seller: ohyouwantthis( 84Feedback score is 50 to 99)
Feedback: 100 % Positive

so i put my 26ga galv block off plate in this past weekend. i think there might have been a slight increase in heat radiated out. my install is not textbook, but i think it did help. since the stove is in the firebox alcove, i made (2) cardboard templates that overlap around the flue collar / liner. i did not seal them together, nor to the masonry firebox walls since it would be near impossible without removing the stove. i figure the block off plate(s) deflect a lot of heat away from the chimney damper and limit the hot pocket above the stove since the plates are just above the masonry lintel. any thoughts ?

I have an exterior chimney - not enough room to insulate - can I use this cerablanket on both sides of the 6" liner in the 7x12 flue (clay tile is 6.5 inches inside diameter - just stuff it in on both sides that are wider)?

That sounds like alot of blanket which = $$$$ depending on how tall your chimney is you might be better off using the vermiculite.

mellow said:

That sounds like alot of blanket which = $$$$ depending on how tall your chimney is you might be better off using the vermiculite.

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My chimney is about 15 feet.

zhukpavlo said:

I have an exterior chimney - not enough room to insulate - can I use this cerablanket on both sides of the 6" liner in the 7x12 flue (clay tile is 6.5 inches inside diameter - just stuff it in on both sides that are wider)?

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I have the same question.
Would it be worth trying to stuff some rockwool or kaowool down the top of the chimney around the liner after everything is in place and before the top plate gets sealed?

is rockwool dangerous, wouldnt it give of little fibers in the air

burntime said:

I insulated the liner and stuffed rockwool around the top 12 inchs before I capped it and have a rock wool layer over the block off plate. Anything will help. Now with the block off plate there is no insulation around the suround which is 1 more place heat comes out from.

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Do you think it would be worth stuffing rockwool or kaowool w/out insulation on the liner? I don't have room for insulation to wrap around the liner.

tkuhe said:

burntime said:

I insulated the liner and stuffed rockwool around the top 12 inchs before I capped it and have a rock wool layer over the block off plate. Anything will help. Now with the block off plate there is no insulation around the suround which is 1 more place heat comes out from.

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Do you think it would be worth stuffing rockwool or kaowool w/out insulation on the liner? I don't have room for insulation to wrap around the liner.

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That's what I did - maybe top 24 inches - and it keeps the liner in place. No room to insulate external chimney.