Need help fire caulking stove chimney to pass inspection

[ben5243]

Quick introduction - had installers replace an old wood stove with a new (Hearthstone Phoenix) and an ICC Excel chimney.

The chimney goes up from the first floor through the support box then offsets and up through the attic and roof. It goes up through a corner of the master bedroom closet which was never enclosed but I'm now remodeling the entire master suite (moving the closet and bathroom walls around) and the chimney will be enclosed.



I just had the inspector come for framing inspection which is the last thing I need before sealing up the walls and he didn't pass me because there's gaps around the chimney that need to be "fire stopped". I tried to ask what would be the proper way to do that but he basically said whatever the manufacturer says is supposed to be used.

I'm having trouble figuring out how to properly do this. The stove has been installed for over a year and when I have a good fire going the upstairs chimney gets too hot to keep my hand on. I read through the ICC Excel instructions but there's nothing about draft blocking or fire stopping. It does say you can frame up to the support box so I do need to fill in the gaps at the floor with subfloor which is easy, I just don't know about the ceiling.

I'm also worried that when the chimney chase is completely enclosed and air sealed it will get absurdly hot inside. All the ICC Excel instructions have is this:


(Page 9) (broken link removed to http://icc-chimney.com/c/icc/file_db/docs_document.file_en/XLUSA-II_2012-01.pdf)

The only thing in the instructions is:

Do not fill the air space around the chimney with insulation or anyother material. Do not fill the factory built supports or radiation shields with insulation. Insulation placed in this area could cause adjacent combustibles to overheat.​

It seems like that would apply to the gap between the chimney and radiation shield in my picture below.

Here are the two areas that need to be "fire stopped":



Any recommendations or products to search for would be much appreciated. Thanks!

 

[begreen]

Call Excel support and request written verification. Then submit this with the factory documentation.

Yes, the interior of the chase will get warm, but it should not be dangerously so if clearances are properly honored. You could add a top an bottom vent for convective cooling of the chase.

 

[ben5243]

I sent them an email to hopefully get something in writing and I printed out everything I can find for instructions but I will call monday morning when they're open.

How would the vents work?

The inspector basically said if a fire started inside the chase where would it go? Up... so the space between the chase and attic has to be air sealed to prevent a fire from spreading.

I assumed the small gap of space around the shield allowed enough air to escape up to prevent extreme temperatures inside an enclosed space which is why I don't want to caulk that sealed.

 

[begreen]

It looks like you have the proper Excel firestop in place. Is there an attic insulation shield above it with the storm collar as shown? If so, that is the flame containment.

The chase is normally not vented. The pipe will get up to about 130ºF normally. That is a bit too hot to hold one's hand on, but safe for the drywall. If you want to vent it you could put a 4x10 grille at the bottom and top of the chase to let heat convect out into the room, but that probably would not contribute to the room heat if it is in a closet.

 

[webby3650]

Sounds like they are wanting you to seal the gap where the pipe goes through the fire stop and support box. Typically that’s not necessary and on some products it actually says NOT to use any sealant in this location to allow air flow.
If you do seal it, 100% silicone will hold up just fine. The inspector might want you to use the red high temp though.

 

[ben5243]

Thanks all, I really appreciate it.

The attic space the chimney passes through is actually only about 12" high before the roof penetration. The radiation shield (ICC 6ERS) sticks up into the roof flashing so there's no actually space for a storm collar and the installers didn't put one in. The only thing I could maybe do is trim the radiation shield down and add a storm collar

Here is what the radiation shield up above the ceiling looks like.


The inspector was right to call out the gaps around the support box in the floor but I think he was just overall unimpressed with the look of the radiation shield and beat up and patched drywall and was trying to dig deeper.

I laid new subfloor around the support box so the gap is at most 1/4" all the way around

I'll run a bead of the red firecaulk stuff around the exterior of the support box but I'll wait to see what ICC says about the radiation shield at the ceiling.

I pulled down the radiation shield and patched up the drywall a bit nicer and reinstalled it flush with the drywall instead of having the drywall around it like before. Overall it's much more pleasant to look at and I probably should have done this before inspection.

 

[webby3650]

I don’t see a problem with the gap. Caulking certainly won’t hurt anything. Don’t do anything with the radiation shield, the only purpose of the storm collar is to prevent insulation from being blown into the shield. Since it terminates in the flashing, I see no problem with it.

 

[ben5243]

Got a response back from ICC:

Thank you for your e-mail, there is no material approved by ICC to seal the gap between the outside of the chimney pipe and the radiation, as you mentioned our instructions specifically say :

This includes high temperature silicone, the gap(airspace) needs to remain free of any sealant, insulation, etc.

Hope this help!​

I'll call for a re-inspection tomorrow and have this printed out. Thanks everyone!

 

[Dobish]

the issue that he has is that there is a requirement for any hole that goes between levels to be properly sealed, to prevent fire from spreading. I'm guessing he was happier with what you did, since it could be considered sealed now?

he just didn't like the big gap in the drywall.

 

[ben5243]

That's basically what he said- his only concern was "fire blocking between floors" and said if a fire started it could pass through that gap and go into the attic.

Once he came back and I told him a typical installation has a storm collar at the top of the radiation shield and in my case the radiation shield goes up and above the roof sheathing. Also showed him the manufacturer doesn't approve anything to fill the gaps there and he said it was okay since the radiation shield goes all the way up.

His concern was about the gap around the chimney pipe but the unfinished drywall seams probably drew more attention to it than it would have otherwise. Anyway, he passed me so I can seal it up.

I did measure the surface of the chimney pipe to the nearest framing stud and it's about 3.5" (although had I put a stud directly in line with the bottom section it would have been 2")
I'll probably be pretty nervous the next couple fires in the fall and put a temperature probe through the drywall and see how hot it gets inside the chase but everyone I've talked to says it will be fine.

Anyway, thanks everyone!

 

[kennyp2339]

I have a very similar setup chimney wise and have not had an issue with heat at all. My stove is in the basement and I went strait up with it, ceiling support box in the floor of the dinning room, class A pipe straight up, once through the ceiling into the attic I have a fire stop shield (same thing with the small gaps) then into the attic space and out through the roof.
IMO the fire stop shields are kind of a joke to me, they really don't stop anything if there's really a fire, all its going to do is buy you time (an extra minute can save a life) How the shield works is it stands the pipe off within the shield (almost like a air cooled wall shield) so if there's a chimney fire there's a buffer on the class a to any potentially close combustibles allowing that pinch point to be air cooled and hopefully not catch anything in the pass through of spaces on fire (sheet rock, ceiling joists, insulation).