# insulation in wall behind wood stove ?



## sullystull (Sep 28, 2008)

I am in the process of remodeling my living room.  I plan to install manufactured stone on the wall behind my wood stove.  Clearance is in issue--I will have the minimum distance required to the nearest combustible material.  I would like to insulate this wall behind the stone but will need an insulation that can't be considered a combustible.  I was going to order some Kaowool.
Or...is there a better product to use?  I will need approximately 40 sq ft.


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## treefrog25 (Sep 28, 2008)

Hi, 

I cant offer much help other than the link below, but I too am trying to get my installation 'up to code', 
just so the insurance company doesnt have an excuse not to pay if there was a fire.  I pay the premium 
every year so I dont want to be throwing $ away just for non-compliance to a standard. 

There is this link where you can read the technical standard on this.  Its called NFPA 211. 
You have to create an account/pwd and its set up so you cant print, only read.  The doc
can be bought for around $35, or you may find it in the library.  Interesting that the online doc 
is dated 2003....maybe its never been changed since then. 

http://www.nfpa.org/freecodes/free_access_document.asp?id=21103


The question which I am looking for an answer to is 'is drywall considered a 'combustible' surface. 

Tim


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## begreen (Sep 29, 2008)

Did you mean you will not have the minimum clearances satisfied? What is the stove?


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## sullystull (Sep 29, 2008)

I have a DW large 2479.  I live in an old coal company house with no insulation.  I have been slowly renovating the house--one room at a time.  As it stands now, I meet the minimum requirements to combustibles (with heat shield on stove pipe and back of stove)--15 inches to the nearest combustible.  To that combustible wall, I will be installing manufactured stone on cement board with a 1" air space behind.  Behind that, I would like to insulate the wall to cut down on draft from the outside.  This insulation will be in front of the combustible wall and therefore fall within the 15" clearance I have.  Therefore, I thought I would need a high temp insulation and not just the standard fiberglass.  Thoughts??


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## begreen (Sep 29, 2008)

Bravo for addressing the lack of insulation. It will make a huge difference in comfort and heating needs. 

In the current situation with the rear exit flue, as long as clearances are already being met, I'd open up the wall, put in fiberglass, then cover in cement board. That way your clearances stay the same. Adding the stone veneer will not change the distance from combustibles (the studs) in this case. 

It sounds like the stove is connected rear-exit. Is top-exit an option? The clearance requirement is 12.5" rear clearance for the stove with the rear + pipe heat shields for top exit. That would give a little more working room. The same chart shows a clearance reduction down to 9.5" with an NFPA 211 wall shield installed, but so far I am not seeing the need for this. 

Just curious, how have you been insulating the rest of the house? Blown in insulation? Tear down to the studs and fiberglass then new sheetrock?


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## sullystull (Sep 29, 2008)

BeGreen said:
			
		

> Bravo for addressing the lack of insulation. It will make a huge difference in comfort and heating needs.
> 
> In the current situation with the rear exit flue, as long as clearances are already being met, I'd open up the wall, put in fiberglass, then cover in cement board. That way your clearances stay the same. Adding the stone veneer will not change the distance from combustibles (the studs) in this case.
> 
> ...



The house is constructed "non-traditionally".  There is no vertical stud framing.  Working from the inside of the house to the outside, it goes as follows: paint, then wallpaper, then sheet rock, then a few more layers of wallpaper, then tongue and groove boards (running vertically).  Behind the tongue and groove boards, running horizontal across the wall are two 2X4's(one at a 1/3rd of the way up and the other 2/3rd of the way up), then another layer of tongue and groove boards.  The 2X4's are sandwiched between the two layers of t&g;.  The outside layer of t&g;is what my siding is nailed to.  Confused...you should be.  I have never seen anything like it...even in other houses around here.  
So, in each room I have torn down all the way to the "outside t&g;" and framed new walls to install adequate insulation.  For the walls where I wasn't so ambitious, I installed blue foam and drywalled over it...better R5 then R zero.

Now, the stove is a top exit, 40" of single wall straight up, then the 90* back through the thimble.  I have the heat shield on the stove and the stove pipe.  Basically, as it stands now in the "gutted" state, I have 15 inches from stove pipe back to the t&g;.  I plan to build off of those boards (once a few structural improvements are made), install insulation, 1" air space, cement board, then stone.


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## begreen (Sep 29, 2008)

Seems like you already have the clearance requirements met. The cement board on the studs as a backerboard for the stone is fine.


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## sullystull (Sep 29, 2008)

here is a pic of the room during construction.  In this picture, I have already ripped down the layer upon layer of wallpaper, drywall, and the inside layer of t&g;(which is now laying in the middle of the room).  The dark lines across the wall (again about a 1/3rd of the way up, and 2/3rds of the way up) is where the 2X4's used to be.  What you are looking at are the t&g;boards that my siding is nailed to.  I will be putting in a header and studs (with insulation).


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## sullystull (Sep 29, 2008)

What do you consider a wall shield...the stone and backer board?
I never thought clearances were too big of an issue--meaning I knew I had just enough.  I just thought if I was going to insulate behind the stone and cement board, I would need a high temp insulation.


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## begreen (Sep 29, 2008)

Yep, that's an odd one. How are you tying the new sill, studs, headers to the other rooms so that there is an integral frame to the house? What ties the exterior sheathing to the new studs?

As far as clearances, considering the state of demolition, I'd build as stated - fiberglass between studs, then cement backerboard and stone veneer. At some point ya got to wonder if an additional few inches is needed, maybe it would be easier to add a short extension between the elbow and the class A? Extending the hearth may be required, but that seems trivial to what you're tackling.


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## begreen (Sep 29, 2008)

sullystull said:
			
		

> What do you consider a wall shield...the stone and backer board?
> I never thought clearances were too big of an issue--meaning I knew I had just enough.  I just thought if I was going to insulate behind the stone and cement board, I would need a high temp insulation.



The clearances to combustibles will be to your new studs. What is the current distance from the exterior sheathing to the back of the stove? If it is greater than 18.5" then I think you are good to go.


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## sullystull (Sep 29, 2008)

It's funny you mention these things.  I like the location of the stove and don't want to move it out any further...causing me to have to rebuild my hearth (I have to draw the line somewhere).  As for tying it all together...well, I'm doing my best and no matter what, I keep saying to myself it's better than it was.  I mean...who puts wall paper on their ceiling


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## sullystull (Sep 29, 2008)

The distance from the t&g;(what you see in the pic) to the back of the stove is the 15".  I will probably not add studs directly behind the stove...just on either side of the windows, with a header across the entire top of the wall.  If you notice in the pic, I also have hot water baseboard heat registers to deal with.  Bringing the wall out (with studs) in conjunction with the thickness of the stone, would interfere with the registers.


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## begreen (Sep 29, 2008)

I saw the hw baseboard heat and assumed it would be moved outward to clear the stud wall, guess not. You could use 1" micore behind the backerboard. That would give you a little insulation there.


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## Highbeam (Sep 29, 2008)

What's the reasoning behind the 1" airspace? It seems to add great complication to your setup and appears to add no function. You're not building to NFPA, you're building to the manufacturer's specs and you've already met them with the stove's location. Your clearance to comustibles is measured from the combustible surface and the cement board is not combustible.


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## sullystull (Sep 29, 2008)

The 1" was just for extra protection.  I can afford to build the wall out an extra inch but not 3 1/2" for the studs.  My plan would be sufficient with out the insulation, i was trying to make it a little more efficient.


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## fjordrr (Oct 2, 2008)

I was looking for a non-combustible insulation too, for an exterior wall behind my new wood stove.  My initial research has turned up "thermafiber" and mineral wool batts.  Not sure where to find them around here, tho - I don't think Home Depot/Lowe's carry that kind of stuff.


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## G-rott (Oct 2, 2008)

sullystull said:
			
		

> I will be installing manufactured stone on cement board with a 1" air space behind.  Behind that, I would like to insulate the wall to cut down on draft from the outside.  This insulation will be in front of the combustible wall and therefore fall within the 15" clearance I have.  Therefore, I thought I would need a high temp insulation and not just the standard fiberglass.  Thoughts??



Mineral Wool insulation will do the trick but that stuff is nasty,  you will want to cover is up and not leave any air space.  
If you need to, steel studs or channel will work in the place of studs to support your cement board.(non-combustible).

Your local Drywall/Gyprock/Wallboard supply house usually stocks Mineral Wool in some form, and it's cheaper than ordering it from stove dealer or online and paying freight.   

Good luck and keep us posted.


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