Hearth pad for Vermont Castings Encore - thin as possible

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My husband and I want to build a permanent (non moveable) hearth pad for a new Vermont Castings non-catalytic wood stove. It's replacing an old wood stove that we have already removed. We have also removed the original pad, which was just standard tile grouted directly to the subfloor!

I've read the articles on the hearth.com web site, including the VERY excellent Hearth Design for Wood, Pellet and Coal Stoves article. In fact, I've been reading this web site for years for all of my firewood and wood stove information. :) But I need a little help with the specifics of our situation, and a little help understanding what the Encore manual says about hearth pad requirements.

We have a 4'x5' space of subfloor ready for the pad, surrounded by 3/4" solid hardwood flooring. We would like to keep the pad as close to flush with the floor as possible. In other words, we would like it as close to 3/4" thick as possible. But thicker than that is acceptable, and as I understand it, is probably necessary.

The stove sits in the middle of our small living room, piped to a brick chimney in the middle of the house. (Pipe and chimney are all ready to go – nothing extra to do there. Clearances are all good – no walls anywhere near where the stove will sit.) So the pad is something we walk over all the time. If it needs to be more than 3/4" thick, we'll put a curved wood molding around it to prevent toe stubbing and make it easier to roll furniture over it.

As I know has been mentioned in other threads here, the current Vermont Castings Encore manual states, "For installation with the heat shield attached, use an approved 1/2” (13 mm) noncombustible hearth pad with k = 0.84 BTU in/ft2 hr °F or an equivalent material with an R-value of at least 0.59."

What confuses me is this part: "approved 1/2" (13mm) noncombustible hearth pad." Is there really something out there that is only 1/2" that satisfies heat resistance requirements? I know they're talking about prefab stuff. But what is it made of, that it satisfies their requirements in such a thin pad?

What we had hoped to do is lay something fairly thin (Durock, etc.) and then lay 1/2" thick slate tile (Home Depot stuff, all prepped and ready to lay) on top of that. But that doesn't achieve the necessary r-value of .59.

I'm reading more threads here and finding some of you recommending avoiding this tile, and Home Depot tile in general. Maybe that's a good thing. We could use thinner ceramic tile instead of the 1/2" tile we've been planning on.

I've read here and elsewhere about Micore 300, but it sounds like it's going to be hard to get where we live and might take significant time to shipped. So unless it's our only hope, we'll probably have to skip that solution. (If anyone happens to know where to get it quickly around here, please let me know. I know there are dealers in Denver, but they're 1-1/2 hours drive from here.)

And I'm just noticing rock wool or fiberglass batts mentioned in the K Values – What does it all mean? article. I don't see much about that anywhere else. Where would one get that in a form that would work for this, and how would it be used in a floor installation?

Any help is greatly appreciated. We'll be picking up the stove next week and we're currently heating with electric baseboard heaters until we get this thing installed. It would be great to be up and running with the new wood stove ASAP – but of course, safely. :)

- Rachel
 
3/4" of an inch is going to be a challenge without an insulation board like Micore. If you can locate it in your area (check with McGuckin Hardware in Boulder), and if the subfloor is well supported and very rigid, then you could make it out of 3/8" micore, 3/8" cement board, then tile. But my preference would be not to compromise stiffness and use instead, 3 layers of 1/2" Durock (R=.52) + then the slate or tile. Trim with a nice matching or contrasting hardwood border.
 
BeGreen said:
3/4" of an inch is going to be a challenge without an insulation board like Micore. If you can locate it in your area (check with McGuckin Hardware in Boulder), and if the subfloor is well supported and very rigid, then you could make it out of 3/8" micore, 3/8" cement board, then tile.

Yes, 3/4" seems impossible. I'm just looking for a solution as thin as possible.

Why do you suggest Micore plus cement board? Wouldn't Micore on its own be enough in terms of R-value? Or is it that Micore isn't rigid enough?

I just had another thought, but I have no idea if it's viable. Could the stove be elevated on a small platform, e.g. brick, to bring it high enough above the surface of the hearth to reduce the bottom heat? Could the hearth pad then be a lower R-value, and thinner?
 
That's correct. Micore is not suitable as a tiling substrate. It is pretty soft stuff.

Yes, the stove could be on an elevated platform, but that might not be too convenient for a top loading stove.
 
BeGreen said:
Yes, the stove could be on an elevated platform, but that might not be too convenient for a top loading stove.

It's only 25" tall, so I'm thinking that's not a problem. Standing here with a measuring tape it feels like I could add several inches in height and still very comfortably load it. But I've never used a top-loading stove, so I'd very much like to hear anyone's input on that. :)

Honestly, I was ignoring the top-loading option, thinking I'd prefer front-loading. But I can see from the manual that this might not be true. So I'd love to hear anyone's experiences on that subject as well.

If loading isn't a problem, elevating the stove itself would certainly make our center of the living room hearth setup a LOT more liveable. So... following up on that idea, how much would it have to be elevated? Is this definitely a good solution in terms of bottom heat and safety?
 
Hi Rachel - I had a VC Encore and I think you'll learn to appreciate top loading. There's no ash spillage to worry about, and that's very compelling. It's also just plain convenient. My feeling is that you won't have any trouble top loading if you elevate the stove a few inches.

So you're thinking you'll have a 4'x5x tiled area (fireproof), and you'll have sufficient R-rating right under the stove to satisfy the .59 requirement? If so, it seems like that should work. Hopefully, one of the installers will respond to confirm that.

I'm on the south edge of Fort Collins, btw. I just replaced a gas fireplace with a new wood stove and I'm so glad I did.

Good luck!

-john
 
johnstra said:
Hi Rachel - I had a VC Encore and I think you'll learn to appreciate top loading. There's no ash spillage to worry about, and that's very compelling. It's also just plain convenient. My feeling is that you won't have any trouble top loading if you elevate the stove a few inches.

That sounds great. And compelling. :)

So you're thinking you'll have a 4'x5x tiled area (fireproof), and you'll have sufficient R-rating right under the stove to satisfy the .59 requirement?

Correct. I did say just brick for the elevated portion, but of course it would also need enough of something with a higher R-value to comply with the requirements. So I guess a few layers of Durock, then something like brick just to lift it further? If that works, I think we've got a beautiful solution.

And in reality we'd lay a sheet of cement board under the tile, too. So maybe 3/8" cement board, thinset, and 1/4" tile? Not a high R-value, but high enough if the stove is elevated on a smaller platform N inches above that surface?
 
With a few layers of durock, there is no need to elevate the stove. Cement board is R-.52/inch of thickness. 3 layers = 1.5" = R-.78
 
BeGreen said:
With a few layers of durock, there is no need to elevate the stove. Cement board is R-.52/inch of thickness. 3 layers = 1.5" = R-.78

Well, yes, I was shooting for overkill in terms of R-value AND elevating the stove some more, since I'm talking about the elevated portion only being a little bigger than the footprint of the stove. I was thinking that more of the hearth area needs either protection from and/or distance from the heat? But maybe not...
 
That's good planning in case the VC doesn't work out. If that's the goal, get a good insulator like 1/2" micore under the durock.
 
pixelmountain said:
BeGreen said:
With a few layers of durock, there is no need to elevate the stove. Cement board is R-.52/inch of thickness. 3 layers = 1.5" = R-.78

Well, yes, I was shooting for overkill in terms of R-value AND elevating the stove some more, since I'm talking about the elevated portion only being a little bigger than the footprint of the stove. I was thinking that more of the hearth area needs either protection from and/or distance from the heat? But maybe not...


I asked a local lumberyard about Micore, the guy hadn't heard about it,made a few calls to check and had some for me in a few days.
 
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