Heat shield with cement board AND sheet metal?

[Tall Tree]

Hey everyone!

Long time reader first time poster 🤟🏻

I'm building a hearth for a Jotul 602 in a small cabin. I'm meeting all requirements for reduced clearances.

For the heat shield, I'm planning use:

1/4" Hardie board cement board, with a 24 gauge steel sheet metal secured to the back of the hardie board, with the standard 1" air gap to the wall, and then 1/2" Hardie board cement board as wall panelling behind the stove.

I understand a 24ga steel sheet metal is by itself sufficient for a heat shield. I'm adding the 1/4" Hardie board primarily for aesthetic purposes and plan to skim coat with actual cement or microcement all the cement board around the hearth for a unified aesthetic.

So — I'm wondering if securing the 24ga sheet metal to the back of the Hardie board creates any potential problems.

For example, would the hardie board affect heat radiation? Would heat get "built up" between the sheet metal and cement board?

I know I might be splitting hairs but the cabin is essentially a bedroom so I want to be extra double sure on safety.

Any thoughts?

Thanks!
M

 

[Whitenuckler]

Hey everyone!

Long time reader first time poster 🤟🏻

I'm building a hearth for a Jotul 602 in a small cabin. I'm meeting all requirements for reduced clearances.

For the heat shield, I'm planning use:

1/4" Hardie board cement board, with a 24 gauge steel sheet metal secured to the back of the hardie board, with the standard 1" air gap to the wall, and then 1/2" Hardie board cement board as wall panelling behind the stove.

I understand a 24ga steel sheet metal is by itself sufficient for a heat shield. I'm adding the 1/4" Hardie board primarily for aesthetic purposes and plan to skim coat with actual cement or microcement all the cement board around the hearth for a unified aesthetic.

So — I'm wondering if securing the 24ga sheet metal to the back of the Hardie board creates any potential problems.

For example, would the hardie board affect heat radiation? Would heat get "built up" between the sheet metal and cement board?

I know I might be splitting hairs but the cabin is essentially a bedroom so I want to be extra double sure on safety.

Any thoughts?

Thanks!
M

I'm not sure why the metal is required. If you use 2x cement board with metal studs would that not meet the requirement?

 

[Tall Tree]

As I understand it, heat can pass through Hardie board. It's considered non combustible but will not radiate heat away from walls, especially 1/4" board

So Im thinking to use the sheet metal behind the hardie board to radiate heat and the hardie board is basically aesthetic.

Also the studs are wood.
The layers would look like:
-Wood stud framing
-With Rockwool insulation
-Poly/plastic vapor barrier (I'm in Canada)
-1/2" Hardie board wall panelling
-1" air gap
-24ga sheet metal secured to the back of a 1/4" Hardie board for the heat shield
-8" space
-Jotul 602 stove


So I'm basically wondering if I run into any safety concerns with a 24ga sheet metal secured to the back of a 1/4" Hardie board

🤔

 

[begreen]

If the goal is for a skim-coat finish, all that is needed is the 1/2" cement board on 1" spacers with it being at least 1" off the floor and open at the top. The metal is superfluous and will offer little to no gain.

Is this for an original 602 or a modern one with the secondary rack? What is the final clearance that is hoped to be achieved by the wall shield?

 

[Tall Tree]

Thanks,
...it's the Jotul 602 v2 with a secondary burn.

Rear Clearance is: 8" to combustibles with double wall pipe and heat shield.

Manual says:
"The wall protector must be non-combustible, such as a minimum 24 gauge galvanized steel or its equivalent"

I know 1/2" cement board will typically suffice, but I think I'd prefer the reliability and functionality of the sheet metal to protect and radiate heat etc and then use 1/4" cement board on top /in front, for aesthetic purposes and to better substrate support a skim coat.

It's definitely all superfluous 😆 I'd be happy to go with simple but... aesthetics get me every time.

I'm probably starting to answer my own questions but definitely appreciate the advice!

Thanks!

If the goal is for a skim-coat finish, all that is needed is the 1/2" cement board on 1" spacers with it being at least 1" off the floor and open at the top. The metal is superfluous and will offer little to no gain.

Is this for an original 602 or a modern one with the secondary rack? What is the final clearance that is hoped to be achieved by the wall shield?

 

[begreen]

In the case of the Jotuf F 602 v2 the rear heat shield spec is for part number HS50, not a wall shield which only affords an 11" clearance.

4.4 Using a Rear Heat Shield to Reduce Clearance
The Jøtul F 602 V2 optional rear heat shield, PN HS50, may be used only in top-exiting installations to reduce clearance as shown in figures 11,12,13, page 14

The wall shield mentioned in the manual is per NFPA211 spec. A metal shield is one of the options, but not the only one.

NFPA Wall Clearance Reductions

The following table sets forth some of the reductions in wall clearances possible with certain wall construction details. For some further discussion on wall clearances, see: http://www.hearth.com/econtent/index.php/articles/stove_wall_clear

www.hearth.com

 

[Eman85]

https://www.amazon.com/SiliFine-Ins...8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1
I'd think you could sheetrock the studs and use these insulators and just the sheet metal painted black and call it a day.