Need help calculating R-value

[tutu_sue]

Hey all,

With the hope that someone will find this useful - I found on on the net showing how to make wall shields and floor protectors for UL listed stoves from Durock cement board: http://literature.usg.com/pdf/CB198.pdf.

It says that Durock has a thermal conductivity of k <= 0.84 Btu in./(ft.2 h °F) in the minimum dimensions specified by the room heater/stove manufacturer. I was trying to figure out the R-value using formula R= 1/k x T from my Jotual manual. With T being thickness in inches, I calculate an R-value of .60 for the 1/2" inch thick board. Can anyone tell me if .60 is correct?

 

[thechimneysweep]

According to a chart we got from one of our manufacturers, 1/2" of Durorock has an R value of 0.200. You can view the whole chart online at http://www.chimneysweeponline.com/horvalue.htm

 

[Gooserider]

According to a chart we got from one of our manufacturers, 1/2" of Durorock has an R value of 0.200. You can view the whole chart online at http://www.chimneysweeponline.com/horvalue.htm

Thanks for the neat chart Tom, I think it will be very helpful.

Let me check my understanding if I may... We have a raised hearth (about 3") that is under our current side load only, pre-EPA smoke monster. The current stove is about 24" front to back, and there is about 12" in front of the stove to the edge of the hearth.

As I understand the code, If I replace the current stove with a more modern stove of about the same size that has a front door (and it seems like all of them do ) then I will have to extend the hearth some distance further out.

Nothing I've seen says the extension has to be the same height as the original hearth, correct?

What I think would work best in the space is if I can make the extension flush with the main floor, or fairly close to it. As far as I can tell without invasive dismantling, the floor is 2x? joists, with a 3/4" or 1" board planking subfloor (there are gaps betwen the planks, they aren't T&G) covered with 3/4" particle board. The floor is carpeted with a fairly typical grade carpet and pad.

From looking at the chart, It appears to me that if I was to remove an appropriate width strip of carpet and the particle board, I could then put a layer or two of 1/2" ceramic board (Fibrefrax or Micore - any reason to prefer one or the other?) to get the needed R-value and then cover that with any sort of fireproof floor treatment (tile, stone, etc...) and be reasonably close to the level of the rest of the floor. Is this a reasonable approach? Would it be code compliant as best you can tell? (I realize you can't totally judge what you can't see)

Talking with the GF, she seems to like the idea of covering the entire living room floor with the same stuff I used for the hearth extension. If I did that, it would certainly solve the question of being flush with the rest of the floor, but would I need to do anything to mark out the "fireproofed" part of the floor from the rest of it?

(Elk or anyone else with relative expertise feel free to chime in as well...)

Gooserider

 

[thechimneysweep]

You're entitled to install your floor protection extension flush with the existing flooring in front of your raised hearth, as long as you provide the thickness of the material you choose to reach the R factor your stove requires. We call these "step-up" hearths, and often use this technique when the hearth would protrude into a traffic area, for example.

 

[Gooserider]

That sounds great, as it won't be to difficult to do, and won't make the useable space in the room any more difficult.

Gooserider