Close quarters attic - chimney installation

[canuseemenow00]

I am installing a Selkirk chimney installation kit from Lowes. The Jotul F-100 Nordic is going to be near the outside wall on a 6/12 hip roof about four feet from the corner. There is little room between the ceiling joists and roof decking. Would it be OK to install the included insulation shield so that it protrudes the roof slightly under the flashing and if so is it acceptable for the side of the insulation shield to touch the roof joist?
In addition I am trying to confirm the hearth and wall protection. Is manufactured cement stone on 1/2" Durock on OSB acceptable hearth protection? The walls will also have the manufactured stone on 1/2" Durock attached to wood studs. The stove is spaced the minimum requirement of 10" from the stove corner to the studs. Will I need to be concerned with conductivity from the cement products to the wood studs and kraft backed insulation?
I've done general remodeling for myself and for hire as well as field service in technical and mechanical fields. I usually adapt to a new procedure quickly. I just need some help with the details, especially when the installation is not textbook.
Thanks in advance for your expert opinions.

 

[edthedawg]

Checking the manual ((broken link removed to http://www.jotul.us/FileArchive/Technical) Documentation/Wood Stoves/Jøtul F 100 Nordic QT/Manual_F_100_USA_P03_090608.pdf), it looks like you don't have a min R-value req't for a non-alcove installation. Alcoves require min R=2.0. You would do well to know your R-value in case you sell the house or decide in the future to swap out the stove. For that reason, you might want to shoot for the 2.0ish min value, but that's just my opinion.

Your hearth sounds like it adds up like this:
Cement product of undetermined thickness - R=~0.1 / inch thickness
1/2" Durock - R=0.2

So you're really not insulating much there - probably in the 0.3 - 0.4 range? Maybe you want to re-think it, but it doesn't appear to be mandatory.

Your manual also states you can run any non-combustible material w/ the bottom heat shield. Are you installing that? Otherwise, without the shield, it seems to indicate you need a UL-listed hearth board, which you could place on top of your concrete product. Your noncombustible material or hearth pad must extend the full distance out front, back, and sides. I would strongly recommend using the Canada standard (18" from the front panel) as I recall a posting here stating the US was adopting this standard. Plus it's just a really good idea to have a nice big hearth (over mins, esp near the loading door). Stoves can really spit out some sparks and embers!

As for your walls, they sound like they qualify as "unprotected" insofar as you are not adding air-spaces. To avoid an issue w/ your inspector, I would push for the furthest corner protrusion of the stove to be a full 10" off the surface of the wall, not subtracting the thickness of the noncombustibles, as you appear to be doing. Not saying your way isn't potentially safe, but the manual (the best I can interpret on page 13) is drawn showing dimension "L" to the surface of the unprotected wall - not to the nearest combustible material within it.

Can't help you w/ your Selkirk installation.

Hope you find this useful and welcome to the Hearth!

 

[canuseemenow00]

Thank you for your response. After reviewing my installation instructions, it looks as though the F100 comes equipped with a bottom heat shield allowing for the use of any noncombustible material under the stove. It looks like it only requires a UL listed hearth pad if the heat shield is removed. As far as the walls, I'll have to give some additional thought to it. I understand what you are saying, but if it is unnecessary to move the stove away from the wall, I'd rather not, because moving it further from the wall would require me to move it further into the middle of the room due to the hip roof. I appreciate your input and look forward to any additional input from you or any others in the field about this or the installation shield.

 

[edthedawg]

If I read the manual and understand NFPA-211-compliant wall protection properly, you could add the necessary protectors and get even closer to the wall. The min requirement drops from 10" to 7" to the wall surface behind the protector.

And with 1" spacers and 3/4" protection, you'd wind up down around 5" min. off that protection surface.

Good luck!

 

[DAKSY]

Would it be OK to install the included insulation shield so that it protrudes the roof slightly under the flashing and if so is it acceptable for the side of the insulation shield to touch the roof joist?

If your insulation shield is the same dimension as your ceiling support box,
it can be in contact with rafters, trusses or joists, as the required clearance is built in.
As far as protruding thru the roof under the flashing, I don't see a problem, but the
attic shield can be cut with snips to match the roof pitch, & that's how we install em...
The MAIN thing is to keep insulation away from your class A chimney...
HTH

 

[canuseemenow00]

Thanks for all the great info. I also contacted the dealer where the stove was purchased for his input. My plan is to install the insulation shield peeking through the roof as long as there is no conflict with the flashing. I will be keeping my stove to wall spacing as is to avoid a major relocation. I'll also have to fore-go the space-out of the noncombustible wall since the aesthetics of the knotty pine scribed into the irregular stone would certainly be compromised. This is a small cabin type structure 150- 200 feet from the house. The stove won't likely get any long term burns. But if necessary I have an idea of using a small freestanding heat shield to compensate. In fact if something like that is available I wouldn't mind being pointed in that direction. I was also thinking I might want to embed a sensor in the wall to monitor the amount of heat getting in there if anyone has any ideas on that item.

 

[edthedawg]

I wouldn't bury anything in the wall. just get a cheap 0-1000F IR thermometer and periodically check the wall surface temp. keep it under Bad Numbers. ISTR 180F is a bad number.