Thermix / insulation question

[gspro]

This is the chimney - interior chimney, 8x13 flue liner, 6" ss liner, 30 ft tall. I posted here about a chimney fire last year, but have not fixed anything yet. Had a stove guy look at the chimney, said he saw some bad tiles, and that I'd need a double wrapped liner. So, given that is correct:
If I were to ovalize the existing liner, I read on this site that it works to use a piece of pvc and roll it down the pipe. How much though? Do you make a frame or channel out of 2x4's or something so you know how much to compress it? I think I'd have to ovalize to get a double wrapped liner down the flue, right?
When I mentioned to the stove shop (that quoted me 2k for a wrapped oval liner installed), I asked about vermiculite or an insulating pour in product, and they told me it wasn't sufficient because you can't know if the liner is centered in the product, or if it's touching the clay tiles. So if I were to get thermix or vermiculite, would I be able to jiggle the liner around enough in the chimney to get it completely surrounded by the pour-in insulation? I'd much rather do this that pull the liner, bend it, wrap it twice, and hope I'm able to get it back down.

 

[ikessky]

Do you have a small piece that you can ovalize, double wrap, and test in the flue? With your previous chimney fire and the bad tiles, I would be more apt to go with the wrap insulation also. That way, you guarantee that the liner is fully insulated and that you are safe.

 

[MountainStoveGuy]

gspro, i just read through your old thread, and wow. thats crazy. I would not put this on insurance, because the liner was not installed with insulation in the first place, which puts it out of code. I would pull the liner, and replace it with a rigid smooth wall liner and insulation. This is going to cost some change, but the integrity of the wood might be compromised. Carbonized wood lights off easy. That fire seems severe, and no way would i want any part of a flexible ovalized liner touching the sides of that thing. I would not sleep well unless i knew for a fact that you had no contact. Double wrapped will give you a very safe installation.

rigid liner would insure that you do not touch the sides. Drop down to a 5.5 if you have to. I would rather reduce the flue size then take a chance with the liner touching the tiles.

 

[Wet1]

Dont they make clips or something that can be attached to the liner to keep it centered and off the tiles? If so, I think I'd go that direction and pour in the insulation.

 

[ikessky]

I also just read your post about your fire. Scary stuff. If it were me, I would not do the Thermix. I would ovalize the liner and double wrap it. Drop down to 5.5" if you need to.

 

[gspro]

Dont they make clips or something that can be attached to the liner to keep it centered and off the tiles? If so, I think I'd go that direction and pour in the insulation.

That would be nice, I'll search around a bit. Seems like a good idea, just make them small enough to meet the minimum clearance requirement, whatever that is!

I also just read your post about your fire. Scary stuff. If it were me, I would not do the Thermix. I would ovalize the liner and double wrap it. Drop down to 5.5" if you need to.

Just curious why would you not use thermix?



I'll try to ovalize a piece that I have to see if it fits; How thick is 2 wraps of insulation? If I reduce it to 4x9, would that be enough?

 

[ikessky]

1/2" wrap should bring your liner to 7.25" (not ovalized of course). I'm not entirely sure why he is saying to double wrap it though. Doesn't the 1/2" single wrap insulated liner bring you back up to code?

The reason that I say I wouldn't do the Thermix in your case is because of your chimney's history. How can you guarantee coverage on your liner when it is probably touching the sides in spots? I would personally feel much better with a wrap, knowing that the entire liner is evenly covered. I'm in no way saying that pourable insulation isn't good, I'm just saying that it might not be the best in this case.

 

[Wet1]

I guess the flip side to that is with the pour in insulation, there's a LOT more insulation within that 8x13" cavity. I wouldn't worry about the liner touching the sides, just wiggle the liner as the insulation is poured in and you'll be fine. Even if the liner did touch someplace, the contact area is minimal at best, and heat transfer should be a non-issue, especially given the amount of poured in insulation around it.

Does anyone know anything about the spacers I mentioned above? I know I read about them somewhere, but I don't recall the details.

 

[oconnor]

Why do you have to keep the tiles at all? If you have them broken out, you will have all the room you need to install a rigid liner with the required blanket insulation, and still meet code requirements.

As for the spacers, or thermix, or blankets for that matter - read the manual for the liner system you will be using. Some say that spacers/thermix can be used, some don't, and it all has to do with how they were installed for the testing process.

Each liner manufacturer will have a specified way to insulate thier liner, and that is the only way that an insurance company, or a code inspector, is guaranteed to find acceptable.

 

[gspro]

Why do you have to keep the tiles at all? If you have them broken out, you will have all the room you need to install a rigid liner with the required blanket insulation, and still meet code requirements.

As for the spacers, or thermix, or blankets for that matter - read the manual for the liner system you will be using. Some say that spacers/thermix can be used, some don't, and it all has to do with how they were installed for the testing process.

Each liner manufacturer will have a specified way to insulate thier liner, and that is the only way that an insurance company, or a code inspector, is guaranteed to find acceptable.

How would I break them out?

 

[MountainStoveGuy]

there are specialized tools to do it. One is a chain whip that goes on the end of a drill.

 

[gspro]

is 'double wrapped' insulation referring to 1/4" double wrapped? A couple manufacturers web sites say that 1/2" is zero clearance. Guess it makes sense that when they say double wrapped that they are referring to 1/4" and that single 1/2" would be ok?

 

[MountainStoveGuy]

Yes. 1/2 is the single wrap that is considered double wrapped 1/4".