Time to insulate my ss liner

Use koawool.

vermiculite is flat out known carcinogen.... why not use ceramic fiber? Its cheap and available ,
try HI Temp Refractories in Missouri... many others too.

Rougement said:

Then I got another idea, how about just stuffing kaowool or rockwool up around the ss liner as far as I can go and then pouring vermiculite down on top of that? I can't see a downside but you never know! is it OK to mix two different insulation systems, even though they're both hi temp ones?

I could even sandwich the vermiculite with more kaowool just under the top plate but I'm not sure this would have any benefit.

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I had the same idea - and that is exactly how I insulated my liner. (I used perlite - it's supposed to have less expansion potential than vermiculite.) It was a last-minute decision and, unlike you, I forged ahead without asking any advice.
I still don't see a downside other than this: there is no way any liner manufacturer is going to give a UL listing where the product is approved for a mix of different insulation systems.

So that's not to say there is a safety or functionality issue. But there may be a code/inspection/insurance issue. All the reasons I've since heard that suggest not to do it this way (uneven/incomplete contact between liner and insulation, potential for insulation to be thinner in certain spots, etc.) don't concern me too much. But they might concern your building inspector and insurance agent. So get it approved before you do it.

Do NOT use fiberglass (not just for code reasons - if it melts/contracts you will be shoveling out the hearth). If you stuff the rock wool up as far as you can that will help ensure no perlite sifts down, but will also make it more obviously a hybrid system (as opposed to just having rock wool tightly stuffed in the block-off area and perlite for the remaining length of the liner).

I would not consider this method unless your chimney/clay tile is perfectly sound and the liner would be considered a safe install without insulation.

pellet9999 said:

vermiculite is flat out known carcinogen.... why not use ceramic fiber? Its cheap and available ,
try HI Temp Refractories in Missouri... many others too.

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Is it really? I've heard any newer verm has no asbestos in it. Only the much older verm.

Pilot Joe said:

pellet9999 said:

vermiculite is flat out known carcinogen.... why not use ceramic fiber? Its cheap and available ,
try HI Temp Refractories in Missouri... many others too.

Click to expand...

Is it really? I've heard any newer verm has no asbestos in it. Only the much older verm.

Click to expand...

That is correct. There was a brand called zonolite containing asbestos. They stupidly did not retire the brand name so now generic (safe) vermiculite is sometimes referred to as zonolite.

pellet9999 said:

vermiculite is flat out known carcinogen.... why not use ceramic fiber? Its cheap and available ,
try HI Temp Refractories in Missouri... many others too.

Click to expand...

Give it ten years and so will ceramic fiber :ahhh:

I used a kit to wrap the liner using rockwool. If the liner is not installed yet, this is the way to go. Fiber glass is not rated for high temps. Also, I made a two part block off plate, a larger frame type and then a smaller two halves the fit around the liner.

I did not have much experience with sheet metal either. Just purchased a sheet metal disc for my circular saw, about $3-4, for the longer straight cuts, and some snips for the tight curved cuts. Bought 24 gauge sheet metal from the local HVAC supply house. I was suprised at how easy it is. I also made a rear heat shield for the back of my fire place which I insulated behind it. Also, I was surprised at how hot it gets in the fireplace behind my stove, 200 to 300 F as read by a infrared digital thermometer.

Pellet99 Who said ceramic fiber was cheap. I dont know where your buyin yours but that stuff aint cheap

It is not hard to make a back-off plate you can even do it as a 2 piece plate. get you a piece bigger than you need. cut it to the rough shape you will need leaving 1 measurement long cut the piece in to 2 pieces where the cut will be roughly the middle of the flue. cut a "C" shape in tho the metal where the flue will be. Just slide one over the other with the "C"s like this ( ) to make the hole where the liner goes. Just remember it doesn't have to be real pretty as it will not be seen.

crazy_dan said:

It is not hard to make a back-off plate you can even do it as a 2 piece plate. get you a piece bigger than you need. cut it to the rough shape you will need leaving 1 measurement long cut the piece in to 2 pieces where the cut will be roughly the middle of the flue. cut a "C" shape in tho the metal where the flue will be. Just slide one over the other with the "C"s like this ( ) to make the hole where the liner goes. Just remember it doesn't have to be real pretty as it will not be seen.

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The only catch is in using loose perlite, even the smallest seam or crack or hole will let the stuff sift down. Even if the block-off is perfect to start with, it could be slightly displaced when moving the stove or cleaning the liner. That was what I realized when I put my stove in - taking the tee off the flue collar was going to put some lateral pressure on the liner and the plate.

It is my understanding that some fiberglass insulation is not pure fiberglass but may contain resin and/or dye that could potentially outgas when exposed to heat. Or that moisture could cause it to degrade. So I guess "melting" is not possible, but in this application just a small change in the insulation could be a problem. (For a more typical application it wouldn't be.) Not saying it would happen, but not certain it wouldn't.
Rock wool may have potential problems that I don't know about, but that's where I would (did) put my money.

I am in a similar boat, in that I will be insulating my SS liner. Weather permitting I'll install the liner next weekend. I've decided to go with an insulating wrap instead of a Thermix pour. The appeal of the Thermix is cost; almost half that of a wrap (4-5 bags x $40-ish for Thermix vs. $250-$285 for a wrap kit).

The only thing holding me up from pulling the trigger on a $250+ wrap kit is trying to figure out what's the difference between the foil-faced wrap insulation and a wrap with no foil, such as koawool or another ceramic blanket (ex: http://www.fornobravo.com/store/FB-Blanket-50-p-16286.html). The plain blanket's are much less than the foil wrapped solutions, but are they OK for this application?

I'm kinda hi-jacking (I'll call it piggy backing) Rougement's thread, but any insights into this would be really welcome.

pellet9999 said:

vermiculite is flat out known carcinogen.... why not use ceramic fiber? Its cheap and available ,
try HI Temp Refractories in Missouri... many others too.

Click to expand...

Dude--you referring to the vermiculite sold in the 70's from that asbestos mine? My folks loaded up our attic with that stuff when I was a kid during the "energy crisis".

My understanding is that all vermiculite sold today is batch inspected to be asbestos free.