Rockwool and Class A chimneys

[Klunker]

Building a new house.

Have Masonry heater that needs a chimney thru attic area.

The heater has a 8" outlet chimney stove pipe that stands 8" above the top of the masonry heater.
The top of the heater is 13 1/8" from the ceiling.
I'm putting a Class A chimney adapter over this 8" stove pipe.
So from the top of the heater I'm going right to my class A chimney (Duravent Duratech double wall).
I'm using a radiation shield thru the ceiling and ceiling joists and am keeping the 2" clearance from combustibles from the class a chimney. The radiation shield is extra protection over and above the needed 2".
This runs well above the ceiling joists.

My problem is the center line of the Chimney/stove pipe is 1 1/8 from the edge of the trusses (ceiling joists and rafters). I have to jog my chimney pipe with the 30 degree offset pipes so I don't hit the trusses/rafter joist that is under the roof sheathing. Also the house is having a standing seam metal roof. The chimney has to exit between the standing seams so that the chimney can be flashed on the flat area of the roof and not the standing seam.
I don't have enough space from where the first 30 degree jog is to keep it above the insulation (20" of insulation).
Because of this I can't put a metal insulation guard around it.
My thought is to use Mineral wool insulation above the top of the radiation shield all the way up to well above where the cellulose insulation will be blown. I can cut a hole in the mineral wool blankets to allow the angled chimney pipe to go thru and stack however many blankets I need to get the height I need. Mineral wool being much easier to fit around the chimney vs the steel tube of a insulation shield.

Now I understand that class A chimneys are to have 2" clearance from all combustibles. However mineral wool is not combustible. So I think I'm good to go. This is the point of all the above. Can Mineral wool be wrapped around class a chimneys?

Does all this make sense to everybody?
Thanks in advance.

[rjwoelk]

I would be checking with the guys that make the rockwool insulation, then check also with your fire insurance folks.  DO NOT GET THAT CELULOSE  any were near that chimney, it will smolder  for days and end up burnning the house down.Just saying.

[Klunker]

Thats what I'm trying to avoid by using the rockwool around the chimney.
Rockwool does not burn, withstands temps of 2150F.

My sticking point is this 2" to combustibles in code.

Rockwool is not a combustible, so it should be OK. But I have been told that I can't wrap it around the chimney pipe.
I can't seem to get an answer if it is not combustible why can't it be closer than 2"?
Was hoping there was someone out there that was wise to all this.

[Hilltop366]

To be extra cautious I would avoid putting anything directly against the chimney.

I'm thinking that there is a lot of heat generated at the stove pipe / chimney connection area that requires a air space for cooling.

Would it be possible to put some rabbit pen wire mesh around the chimney to hold the rock wool back from it, thinking that the wire mesh could be put up in pieces and wire tied together if required.  It might need some pieces of metal to hold the mesh off the chimney as well.  I would check with my insurance people as well. 

[thecfarm]

I have no idea. BUT I would follow ANY and ALL manufacturing installations instructions. Them insurance claim people can be mighty picky when it comes to a claim.  :(

[hedgerow]

Before the final design is put in I would run every thing by your insurance company and get them to sign off on it. My insurance company doesn't like wood burning applinces in houses and they don't even like my Garn in my out building. You don't want to have a fire and find out you don't have any insurance because the install didn't get meet there specs.

[Klunker]

Well for posterity I'll add this post.
I called Duravent and talk to a very nice informative man named Nick.
We talked for about 1/2 hour.
His first suggestion was to use a insulation guard and modify it for the angled pipe.
Then only fill the insulation up to the top of the Guard.
This leaves a depression of lack of insulation around the chimney area.
Not a very pleasing solution.
After alot of back and forth his final suggestion to me was call building inspector.
They are the final say as to right/wrong.
So I made the call.
Hes an nice intelligent guy. He agrees that in the real world code is not always able to be to the letter of the code.
Sometimes you need to try and achieve the intent.
Not sure what I'm going to do yet.
But I know that I won't be wrapping the chimney in rockwool.
I'm going to do some fab work and try to get something that is acceptable to my inspector.

[21incher]

Once you make any changes to the manufacturers installation the UL rating is usually lost so it should all come down to your insurance companys approval to have coverage should a problem arise later. Insurance companies can be picky about wood stove installations.