When I installed my Stove pipe in my 300 sq. ft room in Arizona. I did 90s and put it threw the wall under the roof eave.
I wrapped a 2 inch thick Ceramic Insulation around the pipe and I am going to wrap another 2 inch thick piece of Ceramic Insulation around that giving me 4 inches of fire Proof Insulation around my Stove Pipe.
I have a Neighbor friend that is a retired upper end Fireman and he told me that he had never seen anything like what I did.
He also told me that there would be no way that my stove pipe could start my place on fire the way I insulated the pipe.
I took the Insulation out 12 inches on ether side of the wall and contained it with a piece of light Gage sheet metal . I will do the same when I wrap the second layer around the pipe
You can take a Lit up Oxy/Acet. Rose bud torch to that Ceramic Blanket Insulation and hold your hand on the other side for quite some time before you can feel any heat getting threw that Blanket.
