Flex install this weekend - not to plan...

[offroadaudio]

I finally got around to relining my chimney with flex for my Hearthstone Shelbourne.
The chimney has 8 x 8 terra cotta tiles that have some visible hair-line cracks, but nothing bigger.
I bought a 5.5" liner and insulation figuring the 6 5/8" diameter would fit in the 7 1/4" ID tiles - NOT!

So, plan B consisted of removing the insulation blanket and putting the liner in naked.
In the heat of the moment I figured I'd come back with a pour-in Thermix latter. But - I gotta wonder if it would be over kill?
Here is how the installation sits now; inside to outside:

1. 5.5" Double wall 316L Flex with smooth wall interior. (the liner is listed to UL1777 and makes no mention of insulation AT ALL in the instructions)
2. 1" air space
3. terra cotta tile
4. 1" air space
5. masonry block chimney
6. 1" air space between block and house

Understanding I'd possibly miss out on improved draft, slightly cleaner burning flue - but from a safety standpoint, I'm pretty comfortable.
Obviously it's my installation and I have to be comfortable with it, but any thoughts about skipping insulation in the outlined scenario?

 

[btj1031]

I'm not a pro on this, but what you listed looks good to me. Its what I plan on doing this summer. I have an internal chimney so not really worried about liner insullation.

 

[pinewoodburner]

Did you have to get an inspection?
What about your insurance?
If they are good with it and you are good, light it up.
I think most liners need the 1/2" insulation to have the UL listing.

 

[gpcollen1]

My liner is not insulated in my 13x13 - outside wall - chimney. Mine stays pretty clean except for the top couple of feet - depending. I would not sweat your install.

 

[offroadaudio]

Thanks - that's kind of where I am with it. I'm pro insulation, but I'm not busting out those terra cotta tiles to get it to fit!
No inspection here.

Be safe.

 

[BrotherBart]

That double wall liner is what bit ya. That stuff is over twice as thick as single wall liner and eats up flue tile space real quick. With the double wall you should be fine. I had it uninsulated in a 21 foot exterior chimney and the thing drafted like gangbusters.

That stuff is a pain in the butt to wrestle down a chimney ain't it?

 

[oconnor]

The UL 1777 statement on your liner depends on the condition of your chimney - it assumes your chimney is in good gondition and fully code complaint including code required air gaps to combustibles (I don't know how to build a chimney that doesn't touch the house, especially on an outside wall, but that is what code demands of a solid fuel flue, up to 2" of air gap).

For code compliance when the brick chimney doesn't meet solid fuel code, like when it was built as an oil flue and you got ride of the fossil burner to allow for wood, you can insulate the liner to reduce the clearances needed, just like shielding reduces stove clearances. That assumes the liner was tested for an install with insulation - not every liner has been tested with insulation, and it's the testing that insurance companies care about. Just 'cause an industrial shop can create a tube of 316 stainless flue, doesn't meen they have the bucks for an expensive lab test to determine optional ways to use the product, so some manufacturers assume that you have a code compliant flue. But if you had a code compliant flue, you likely wouldn't be shoving a liner down it, and so the circular argument proceeds.

In some instances, having the liner in the tile, and space around the tiles inside the brick chimney, can get you the zero clearance needed to combustibles, but again it all depends on how the company paid to have thier liner tested. It's all about reading the instructions. If the liner manufacturer can't tell you how to insulate the liner, that's probably cause they didn't get it tested with insulation.

Given that your liner is inside clay tiles, and a tight fit too, I don't think you will have too many practical issue like draft problems.

It is a gut level call - so says the guy who is waiting for the tech to come and insulate my flue, which needed to be done to meet code the first time he did it.

 

[offroadaudio]

Yeah - the double wall stuff sure is stiff.
If I had my stove pipe for the final connection, I'd probably burn right away - I'm comfortable with it.
But, the stove pipe is on back-order which gives me time to wrestle with it in my mind, so I'll be back in the air this weekend freezing my tail off and dumping some type of magic slurry in there - DAMN!