Time to insulate my ss liner

[Rougement]

Here's what I'm thinking: I'm gonna go with vermiculite because it's cheap and readily available around here. I'm also going to need some kind of block off plate to stop the vermiculite flowing into the fireplace. My metalworking skills are non existent so I thought of modifying a top plate to fit just inside the clay flue tile and seal it in with some hi temp adhesive.

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.

Any thoughts are very much appreciated.

 

[DAKSY]

Just jam the the rockwool or Kaowool or unfaced fiberglass (yes, I said that) around the liner in the damper area...
You don't hafta reach as far up as you can, unless you're trying to save money on the vermiculite...
Thermix might be a better choice, unless you plan on removing the liner at some point in the future...
Thermix will set up like a rock...

 

[Rougement]

I'm doing this so I can get it all inspected and insured, are you sure fiberglass is going to meet code? I'd hate to do this, have an inspector fail it, pull out the fiberglass and get showered in vermiculite. I doubt my wife would be too pleased either.

 

[daryl]

Use koawool.

 

[pellet9999]

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

 

[branchburner]

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.

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.

 

[jkupcha]

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

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

 

[Rougement]

The vermiculite I looked at had a warning to not breathe the dust but seeing as I'll just be hauling some bags onto the roof and emptying thownsown the flue (whilst wearing a mask) I don't see a problem in this. I did hear that perlite is also a better insulator too. If I can pick up the stuff locally, I will use it. I guess I'll put in a call to the inspector too, see what the official line is.

 

[branchburner]

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

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

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.

 

[ohio woodburner]

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

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

 

[Green Energy]

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.

 

[brokeburner]

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

 

[crazy_dan]

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.

 

[branchburner]

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.

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.

 

[DAKSY]

Do NOT use fiberglass (not just for code reasons - if it melts/contracts you will be shoveling out the hearth)

Fiberglass does NOT melt. It does NOT burn. It is SAFE to use in Terra Cotta flues around SS liners.
It has been tested to ASTM E 84 - Standard Test Method for Surface Burning Characteristics of Building Materials,
& as long as you remove the paper, nothing will burn or melt or outgas...

 

[Rougement]

Thanks for all your help guys. I've seen a few posts in various threads about the suitability of regular fiberglass - some pro, some anti. Is there such a thing as a definitive word on this? I don't recall seeing any commercial product using fiberglass around a ss liner fwiw.

 

[branchburner]

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.

 

[sugarloafer]

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: (broken link removed to 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.

 

[woodgeek]

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

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.