"Millboard" - The Truth!

[jtp10181]

While working with an R & D guy this week we accidentally found a reference to the "millboard" that is so mysterious in the Quadrafire stove manuals. This is from the newest UL 1618 in regards to "Ember Protectors 2".

"The subcommittee has chosen R=0.45 as the minimum thermal resistance required. This value comes from the long accepted benchmark of 3/8" of asbestos millboard with a k-value of 0.84."

 

[begreen]

We talked about this a little while ago. Here are some current manufacturers of non-asbestos millboard. If you go to their site you can find currently available specs.

https://www.hearth.com/econtent/index.php/forums/viewthread/8374/

 

[nshif]

But Quadrafire says 3/8" with metal clad so what R value is that? I gave up trying to figure it out for my 4300 and put down 1/2 " cement board with 2x4 metal studs on top with 2 more layers of cement board over that capped ( soon ) with 2+ " of ceramic rock. It better be enough cause I aint tearing it out!

 

[begreen]

The metal cladding doesn't add to the Rvalue, it protects the millboard with a non-combustible surface. You did well and are ready to go, even if you switch to a stove with a hotter bottom.

 

[nshif]

Thanks BG I needed that vote of confidence, as long as the inspector sees it the same way.

 

[jtp10181]

We talked about this a little while ago. Here are some current manufacturers of non-asbestos millboard. If you go to their site you can find currently available specs.

https://www.hearth.com/econtent/index.php/forums/viewthread/8374/

I knew we talked about it before, and no one (not even me or other Quad dealers) really knew what they were talking about. I also posted not too long ago that someone at Quad told me anything non-combustible at least 3/8 thick would suffice which is not really true. I just wanted to clear the air.

 

[hearthtools]

All the travis manuals just say 3/8 Non combustable