Hearth R-Value

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Fire_Eye

Fire_Eye

New Member
Sep 21, 2007
11
River Grove, Il
I have an older model hearthstone heritage. It is model number 8020. The newer one is model 8021. I read both manuals. The manual for the 8021 stipulates that the hearth protection from combustible surfaces must be 1.2. The manual for my Heritage 8020 only requires the hearth to be a noncombustible material. Am I worrying too much about this? Should I build a hearth that fulfills the requirements for the 8021 or should I just do what my 8020 manual requests? My plan is 1/2 slate_3/8 thinset_1/2 Hardebacker board over the 3/4 plywood sub-floor. aprox 0.3 r-value.
 
How do you plan to get 3/8" thinset? Not really very thin. After the notch trowel and proper setting of the slate I would anticipate 1/8" thickness max of that "thin"set.

If the 8020 is EPA and has clearance requirements other than the generic fire code then I would use that manual and use the non-combustible surface. The non-generic clearance requirements may indicate that the stove was tested and that the hearth requirements are minimal.
 
I believe thinset can be built up to about 1/4" after burning in your first layer. But, it's not always easy to build up that much and keep everything level and not oozing out the cracks (from my limited experience). If you need more than 1/4" you're supposed to move up to a medium based mortar as opposed to using thinset.
 
Hardy backer is made of cellulose; I called James Hardie technical support 1-888-JHARDIE about the lack of R value off their ½ inch hardybacker product. They told me ½ inch hardybacker has no Rated R value, “it conducts heat”. Hardy backer is not the stuff you want behind your stove or under it. WonderBoard or Durock cement boards are R rated and UL Listed for that application. I’ve only used Durock brand board because it is 100% cement with a fiberglass backing.

# note
1/4” hardi backer board is r0.13 per for specs check out this web limk to conform fire resistande and r-value

http://www.jameshardie.com/homeowner/products_backerboard_halfInch.shtml

If it is model number 8020 then follow the model number 8020 manual and Contact Hearthstone about installing your stove. And call you building inspector about installing it before you go to far as some old stoves can not be legally installed now (EDA rules).

[email protected]

http://www.hearthstonestoves.com/

That said More is better build all the r into your hearth you can. Your next stove may need a r-valve you could get NOW by using r rated materials now at little or no extra cost.
 
Thanks for your fast replies. You all are certainly faster than Hearthstone ( I emailed them last week).

How do you plan to get 3/8” thinset?
Click to expand...
I am putting in 24x24 tile and will be using a 3/4" x 9/16" x 3/8" U notched trowel or 1/2 square notched.

If the 8020 is EPA and has clearance requirements other than the generic fire code then I would use that manual and use the non-combustible surface. The non-generic clearance requirements may indicate that the stove was tested and that the hearth requirements are minimal.
Click to expand...

The manual on the 8020 only requires the floor protecting to be noncombustible. The stove is EPA and built Nov 2001. With all the discussion here about r-value floor protecting I was concerned. The only thing otherwise would be in the future if or when I get another stove the hearth would need to be beefed up to meet the requirements. I really wouldn't want to do that now if I don't have to because the 18" in front would eat into my traffic path out the back sliding door to the deck.


What are the generic r-value requirements for the hearth? I am thinking they my be found in the vogelzang manual.

Does anyone know of any other modern EPA stoves with slim to none r-value protection requirements and hearths that only be noncombustible?

Hardy backer is made of cellulose; I called James Hardie technical support 1-888-JHARDIE about the lack of R value off their ½ inch hardybacker product. They told me ½ inch hardybacker has no Rated R value, “it conducts heat”.
Click to expand...

I will take that Hardie "conducts heat" into consideration. If I could get the durock for the comparable price I will use it. Considering my room is wide open and I wouldn't be cutting much of it anyhow. The advantage of Hardie is weight, ease of cutting, and installation (nailing it down). My stove is EPA II built in Nov 2001. I hope the inspector doesn't have a problem with it. If so than I will be burring all my fire wood in the outdoor pit.
 
Hearthstone 8020 is a modern Stove EPA Rating: 2.3 grams per hour and cleaner than the 8021 by .25 grams per hour. Hook that stove up stop looking, just do it.

A stoves installation manual instruction trumps all other requirements. You can build you a hearth above those requirements as you like. Last time I was in Home Dept hardy and durock were close to the same price.

Hearthstone 8020 Specifications
Heating Capacity: up to 1,800 square feet
Burn Time: Up to 8 hours
Heat Life: Up to 12 hours
BTU: Up to 50,000
EPA Rating: 2.3 grams per hour
Maximum Log Length: 20.5"

Hearthstone 8021 Specifications
Heats up to: 1,900 sq. ft.
Burn Time: Up to 8 hours
Heat Life: Up to 12 hours
Size: 55,000 BTUs
EPA Rating: 2.77 grams per hour
Maximum Log Length: 21"
 
If you have room for the height, I'd over build the hearth. Maybe you will want to change stoves in the future and the new stove may require more insulation.

Matt
 
That said More is better build all the r into your hearth you can. Your next stove may need a r-valve you could get NOW by using r rated materials now at little or no extra cost.
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Drift, if just keeping the stove on the contiguous slate floor of the great room is achievable trough meeting the stoves requirements than that is what I will do for the sakes of mobility out the sliding door. To address the future, if the next stove requires more hearth than I will add over the slate some concrete or durock sandwiched micore board. Also getting a heat shield and moving the stove closer to the wall would remove the hearth from near the doorway.

To be clear, my concern was whether the old manual (2001) was printed in a time when r-value hearth protection wasn't considered important resulting in fires and changes in present day requirements. Or maybe in the past Hearthstone did test and discover all the hearth needed was to be noncombustible for the Heritage 8020. Safety is important but I am not going to waste money, time, and living space needlessly.

This job is going to be properly engineered.
 
A stoves installation manual instruction trumps all other requirements. They are tested for safety and certified or failed UL. After that point the instruction manual rules. They can be recalled contact Hearthstone ,you have a great stove.
 
I will take that Hardie “conducts heat” into consideration.
Click to expand...

Just so you know....

HardieBacker is rated as a non-combustible surface. In your case this only will matter if you can achieve your R-value through other means, and wanted to use HB as a good surface to set tile on. I have no experience with Durock and other products, but the HB was super easy to work with (it was like cutting a sheet of peg board - in that after you score it, it simply bends/breaks along the score line). Maybe Durock does the same thing, but after seeing how it was falling apart on the shelves at Home Depot, I couldn't imagine working with it.

However, in my case, all I needed in terms of a hearth for my insert was .026" non-combustible surface. The slate tile I used met this requirement, so the HB for me was just used as a tile set surface for the portion of my hearth that was built up over my sub-floor/plywood.
 
A stoves installation manual instruction trumps all other requirements. They are tested for safety and certified or failed UL. After that point the instruction manual rules. They can be recalled contact Hearthstone ,you have a great stove.
Click to expand...

I appreciate everyone who voiced in on this. I understand the manual trumps all. Next I have to talk to the inspector (haven't applied for the permit) and we will be on our way here.

I emailed hearthstone but did not get a response. Do they have a number I can call?
 
I exchanged an email with Jim the tech man on October 9th. He responded within hours. Do you have the right address? I really want to see this stove lit to see how the cement does.
 
I also was advised AGAINST using Hardiebacker in the hearth protector under the stove by Hardie technical support people. (They did say Hardiebacker was fine for use in NFPA clearance reduction walls) DUROCK which I found worked very easily, is specifically reccomended by the manufacturer for use in floor protectors. My local HD didn't carry Durock, but Lowes did, as well as the only other lumberyard I called.

Note that the 18" hearth clearance in front of your loading door is contoversial, some inspectors will insist on it, even if the manual lists 16" (and the inspector does NOT have to accept the manual reccomendations if Code has stricter requirements....) If you can make your hearth with a higher R-value than required, it may save you effort if you ever want to upgrade to a different stove later, but all you HAVE to meet is either whatever the stove manual says or whatever the inspector requires.

Gooserider
 
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