Air Sealing around cathedral ceiling box

[NBABUCKS1]

I am doing a chimney install and need to air seal around my cathedral ceiling box. Can I use this product? http://www.touch-n-seal.com/gunfoamII.htm

I plan on running double wall pipe (DVL to Double wall chimney) for the span and the my cathedral ceiling is 15 feet above my stove.

The stove will run into the cathedral ceiling box. I want to air seal around the box. What type of external temperatures will the box have?

My main concern is the polyischonerate that is near the box. I am insulating below my rafters with a layer of polyiso. Polyiso is very flamable.

Is there some kind of insulation/firebreak that I can put around the box above the drywall and below the roof deck?

 

[webby3650]

You can put any kind of material around the outside of the box. The box maintains the proper clearance to combustibles, no matter what they are made of. At the roof, it will be more difficult. Can you build a sheet metal chase from the box to the bottom of the roof deck?
Keep in mind that the box itself isn't air tight. You will want to seal all the corners and seams on the box from the inside.

 

[jdp1152]

fire rated caulk, rockwool insulation in the immediate area.

 

[webby3650]

What type of external temperatures will the box have?

100 degrees or less. So, there is no need to do anything special.

 

[Highbeam]

I sealed with regular caulk around mine. That's the point of the box, to maintain clearance to the pipe.

 

[begreen]

Temp should not be an issue but for extra peace of mind maybe use Great Stuff Fire Block?

http://www.homedepot.com/p/GREAT-ST...ng-Foam-Sealant-345372/202023037#.UaTYQlN769E