How to get the Homestead's R-6.6

[rsiros]

Hearthstone Homestead has a R-6.6 requirement for the model with 4" legs. What's the thinnest and easiet way to obtain a hefty R-6.6? The manual states that 1/8" air space is equal to .92 but how do you maintain that consistent space under the stove and how narrow (or wide?) can the 1/8" air space be? Can a bottom heat shield be used instead of a thick hearth and how to fabricate one? Sorry for so many questions but I'm trying to find the best way to do this.

 

[bcnu]

I put in a Homestead this summer. One option was the R6.6 with short legs. I went with the 6" legs and R2.5. Our hearth was still a challenge because of the mantle surround my wife already had. The stove comes with a bottom heat shield, so are you asking about something in addition to that? Micore is a good option to help get the needed R value. You can search this site as there have been numerous posts on using air space to build a hearth. My Homestead is up to 400 degrees at 11 pm and I'm going to fill it for the night. 74 degrees inside and 39 out, and we'll still be pretty toasty tomorrow morning. Sat. night will be our coldest so far - around 27 so perhaps the real heating season is about to begin.

 

[Lignums]

The dealer who sold me my Homestead sold me a hearth pad. It still had to have the 6" legs, because it is located on a combustible floor, and a heat shield, though I think the heat shield was optional, I put it on anyway. Even when the stove is hot enough to make you stand away from it, the underneath is a fuzz more than warm, but not hot to the touch.

 

[Vic99]

I ran into the same issue with my Homestead planning. I too opted for the 6 inch legs with bottom and surround heat shields for my Hearth mount set-up. This brought my floor requirement down to R 2.5.

Also bought a hearth pad from the dealer that gave me an R of 3.1. Looks slick. I got the Cumberland Sky option from Yoder with the thinnest thermashield. Total height of the pad is 2.75 inches.

The thermashield fits under the standard pad and fits together in a way that gives about 1 inch of air between them.

http://www.hearthclassics.com/hearth_pads/index.html

Good luck.

 

[Lignums]

That was the exact same one I have. It is pretty durable, I found that you can drop allot of stuff on it without damaging or marring the surface. A little soapy rag and it comes clean real easy. The only thing I found that chips is the very edge where the top stops and rounds over to the floor. My son over the past few years has been using it as a ramp for his matchbox cars when the stove is not in use. A little black paint covers it up real nice, like brand new.

 

[rsiros]

I talked to an old-timer at a stove shop today and he said that putting a piece of sheet metal under the stove with some "feet" on it (to raise it an inch or so) would do the trick. I'm quite skeptical of this easy fix but what do you all think? I am probably going to have to tear the old hearth out and re-build with r-6.6 in mind... not really what I had in mind. Any ideas for a low-profile r-6.6 hearth?

 

[Highbeam]

The old timers can really steer you wrong when it comes to R value of hearth construction. Back in "the day" you could get away with a lot more. Meeting these requirements is critical to passing inspectino and meeting the requirements is not as simple as being good enough. Your 6.6 is especially challenging.

 

[bcnu]

RSIROS - I found low profile and R6.6 to be quite a challenge. I have quite a large fireplace opening and almost built a small pedestal, around 7" tall, for the stove to sit on(like a mini raised hearth) Fine for the r value but put our mantle surround that much higher. So we nixed that one. Look for Micore. Can't remember now if the 160 or 300 gives higher r value, but you can google Micore and see for yourself. I tore out the 12" raised hearth to make one almost flush with floor. My knees and I are kinda wondering why we didn't keep the higher hearth :-/

 

[Gooserider]

In essence, I haven't been able to find any information on how to get a compliant 1/8" airspace that meets the requirements to get that 0.97 R-value on a "home build DIY basis". A thick stack of Micore, topped with a layer of Durock is about the best I've been able to see that a home-brew pad can get. The down side is that about a 2" thickness of Micore is needed to get to R-6.6, or so the overall floor to stove top height is about the same whether you have the 4" leg R-6.6 version or the 6" leg R-2.5 version....

IOW, you can't really save any space by going to the shorter legs, as you will lose the savings in the thicker hearth pad requirement.

I feel the best approach is to use the 6" legs, unless you are installing on a solid masonry hearth, or other non-combustible setup that will let you not worry about R-values. It is then possible to build an R-2.5 pad that is flush with the floor or at least close to it. (Remove flooring to joists, fill with sisters and blocks to keep floor strength, build back up with 2 layers of Micore, 1 or 2 layers of Durock and tile...)

Gooserider

 

[rsiros]

Two questions... 1. Why/where sister joists (inside or oustside)?
2. Why not fiberglass? There was another thread on here that I saw where a guy used metal studs and fiberglass. He had lots of pictures to follow his progress. I'll have to dig that one up.

 

[Gooserider]

Two questions... 1. Why/where sister joists (inside or oustside)?

If you look at the hearth construction article in the Wiki, it goes into more detail, but essentially the decking on the joists is "structural" and also serves as a fire barrier, and if you remove it, you need to do something to restore the integrity of the floor. Per Elk, who was a veteran home builder as well as an inspector, the best way to do this would be to use a 2x4 sistered to each side of each exposed joist, and recessed down an appropriate distance, to act as a nailing ledge, then cut short 2x?'s to fit between the joists and rest on the sisters,then nail in place. This would give a restored sub floor with the same structural integrity and stifness (vital to your tile job) as you had with the removed decking, but with no added thickness - depending on the original flooring, you now have about 1.5" worth of space to build back up in with non-combustibles. This is enough to let you build a non-combustible hearth pad that meets the requirements of most any stove while still being flush to the rest of the floor.

2. Why not fiberglass? There was another thread on here that I saw where a guy used metal studs and fiberglass. He had lots of pictures to follow his progress. I'll have to dig that one up.

Fiberglass works, but only when it isn't compressed, so you have to have metal studs creating the space that it fills, topped with at least two or three layers of Durock to give a top surface with enough strength and thickness - so you end up with a pad that is 5-6" thick minimum - the OP wanted something "low profile," and the studs and glass approach ain't it...

Gooserider

 

[rsiros]

Thanks Goose. I can picture the sistering now... using them as a ledge and nailer makes sense. I was picturing them being used flush with the tops and couldn't make sense of it. I found someone local who has 1.5" ; 2'x4' mineral wool sheets. Have to buy by the "bundle"- 8 sheets for $26. Does that seem reasonable? He said that it's r-value is somewhere around 4.2/inch, so that should do the trick. Still waiting to hear back from Hearthstone.

 

[Gooserider]

Thanks Goose. I can picture the sistering now... using them as a ledge and nailer makes sense. I was picturing them being used flush with the tops and couldn't make sense of it. I found someone local who has 1.5" ; 2'x4' mineral wool sheets. Have to buy by the "bundle"- 8 sheets for $26. Does that seem reasonable? He said that it's r-value is somewhere around 4.2/inch, so that should do the trick. Still waiting to hear back from Hearthstone.

Can't really help on the prices - I've never shopped for the stuff so I don't know what it should cost. Doesn't sound unreasonable at any rate - sometimes a price is at the point where you aren't going to save enough shopping around to make it worth while - this might be in that category. Having to buy the bundle stinks, but I can see why they want to sell it that way, broken bundles are hard to keep in saleable shape... OTOH, you may get a real bargain if you ask whether they have any broken bundles you could get a deal on...

I'f you are doing the studs and mineral wool approach, I'd guess you'll need two layers, that should give you around R-10 or R-12, plus what you get from the Durock. Remember you will probably want to put the studs on 8" centers or thereabouts - Durock really isn't intended to handle a load when it isn't supported, so it's important to increase the stud spacing and do more layers to get back the needed stiffness and strength.

Gooserider

 

[rsiros]

Using a 4.2/inch r-value, I should get a 6.3 r-value by using 1.5" material alone. With a sheet or two of Durock and some sheet metal, I should be good... right?

 

[Gooserider]

Using a 4.2/inch r-value, I should get a 6.3 r-value by using 1.5" material alone. With a sheet or two of Durock and some sheet metal, I should be good... right?

Probably, but I was thinking in terms of filling the stud spaces. One layer meets requirements, but I like to fill the cavities.

Gooserider