Today's question is a revision of yesterday's liner insulation?

[elkimmeg]

Dead air space, in itself is a form of insulationm, an r-value of .97 per inch. I did a little research last night and so far have not found an r- value for liner wrap. I find clearance to combustiables 1" for 14" wrap and zerro clearance for 1/2" wrap
but no rvalue. The same un wraped insulation is sold but no UL labeling wire mesh can hold in place either Insulation.
Part of the insulating properties is the fibers create an air space
For simplicity take the examlpe of a 6" liner in a 12/12 clay flue and inside demention od 11/11" Centered in that flue would
and blocked of on both ends would create a 2.5" dead air space all around the flue. That dead air space would have an r-value close to 2.5. Is not pouring theromix vermiculite the same a material with insulating properties creating dead air space? and no foil wrap.
Yet some brands carry a UL labeling Even codes mention a lined chimney having 2" clearances b what about 2.5 '' in this case.
Percard has me thinking and looking for answers and explanations. I see how the reflective value of the wrap will help hold heat in but but Insulation also does this and dead air space is insulation Guestion is , Is a centered liner with sealed dead air space enough insulation in a 12/12

We all know manufactures spect other products thay sell. Some make it into code like roofing paper under shingles.

To me that is a blatent code or use to sell additional products. From a practical point of view, if some one screws up the shingling, then the tarpaper is not the answer. There are 350 nail penetrations in the tarpaper for every 100 sq ft of shingling. If the shingles leak, the the water will find the nail and weap into the home tarpaper or not

 

[NFreiermuth]

Elk,

Nice info. It does pose a good question and I can see the search is on for answers.

BTW, I always though the the felt (Tarpaper) was for easy removal of the shingles so they didn't bond to the roof decking material. Do folks actually think it's another weather barrier???

As for Commercial uses, the 15# and 30# felt (tarpaper) is for the either 4 or 6 ply built up hot roofing.

 

[recppd]

Let me ask this question about liner insulation...

I wrapped my liner with 1/2" foil-backed insulation that came with the "insulation kit" I bought. Granted the kit came with the stainless mesh, wrapping wire and hose clamps, but it also cost $250. I found an online dealer who sells 1/4" and 1/2" thick rolls of 2300 degree ceramic blanket for cheap money. They come 24" wide by 25' long and sell for approx. $30-50, respectfully. They are NOT foil-backed, however. Does this matter, or does code require foil backing on insulation when it goes on a liner? If not, you could easily make up your own kit for probably half the price.

 

[DriftWood]

In a class A masonry chimney inspected and passed as such. With inside liner clearances and clearance to combustibles all AOK I see your point.

In a 0 " clearance to combustibles masonry chimney or a masonry chimney that does not pass for other reasons, liner insulation instructions rule. Liners for these were UL tested passed as per instructions, with foil rap-insulation and wire covering. I would not leave it off.

 

[Todd]

Good question Elk. Both hearth shops I talked to in my area said they don't use insulation, it's a waste of money.The draft is fine without an insulation wrap. Even for colder outside chimneys such as mine.

Would the insulation wrap help retain a chimney fire better than without?

 

[elkimmeg]

I will probably touch of a firestorm here but I believe insulation was substituted when thiner gage metal was used for liners. You can get a cheaper liner but now it required insulation for UL listings. There is quite a difference between 316ti and 304 ss liners all 304 require insulation to meet ul code. In the hampton manual of 300i inserts they require only liners but no insulation if an exterior chimney. The problem is the manufactures are testing liners with insulation which the supply and sell Code wise there is no language requiring insulation, only that one must follow the manufacture's listing. odd that no mention of r-value is listed

there is language concerning equalvancy. What if the dead air space equal or exceeded the r-value of the insulation would that not be equalvancy?