Effective Firebox Insulating

[jatoxico]

With the recent cold (single digits) it has become especially apparent that I am experiencing significant heat loss from the back and sides of my insert (Jotul 550) to my externally positioned masonry chimney.

I notice when temps drop I get darkening of my bricks that I attribute to gases condensing on the cool brick and right along the secondary air passages at the back of the insert firebox. This is most obvious at start up and eventually clears if I am burning multiple loads. It is not much of an issue when temps are warmer so definitely temp dependent but no matter what I'm still not getting all the heat I could.

My question is; Is insulating the firebox with kaowool or other appropriate material effective? What's the minimum amount of material I need to use to make a worthwhile difference?

It's been about three years since the insert was installed so I don't remember the firebox dimensions offhand and will have to pull the surround to see how much room for material I have.

The damper and cap area are well insulated with roxul and I don't have any drafts. I'd like to pull the insert to add a block off plate (although I don't know how much difference that will make considering it's pretty well sealed) but would rather do that in the off season. I could add kaowool to the sides now at least but am I wasting my time?

 

[EatenByLimestone]

The blockoff plate will make a huge difference. Even though the top is sealed, you are heating the entire volume of the chimney! The blockoff plate will do 2 things. It stops the air currents going up the chimney, and it reflects heat back into the fireplace. I don't think you are wasting your time by adding the kaowool, but I think you'll get more bang for the buck with the blockoff plate. Next week starting Sunday will be pretty warm days up here. You may be in the high 40s/low 50s down there. Do it then.

 

[jatoxico]

The blockoff plate will make a huge difference. Even though the top is sealed, you are heating the entire volume of the chimney! The blockoff plate will do 2 things. It stops the air currents going up the chimney, and it reflects heat back into the fireplace. I don't think you are wasting your time by adding the kaowool, but I think you'll get more bang for the buck with the blockoff plate. Next week starting Sunday will be pretty warm days up here. You may be in the high 40s/low 50s down there. Do it then.

Well I'm insulated top and bottom so not convinced the block off will help my issue, maybe it will IDK. I know Lowe's carries sheet metal is kaowool available at HD or Lowe's?

 

[weatherguy]

There's been a few members that have done what you're proposing, I think they used kaewool and some put sheet metal painted black in front so it hid the kaewool. If I had an exterior chimney that's what I would do. I know when I touch the back of my fireplace in the basement workshop its pretty warm so if that was outside I'm sure I'd be losing some heat.

 

[EatenByLimestone]

The only place I've seen kaowool sold is at a local hearth shop. They'll have a roll of it. Be prepared to open your wallet wide. It's expensive.

Even if you have insulation stuffed in the top and bottom you are not stopping convection currents. Put the plate in there and then seal the edges with fireproof caulk. http://www.dap.com/product_details.aspx?BrandID=9&SubcatID=2

Remember that it is reflective too.

This should be available at your local hardware store and can fill the gaps between the pipe and the shield. I wouldn't use the silicone here as I don't think it will handle the temperatures.

http://www.ruralking.com/meeco-blac...&cagpspn=pla&gclid=CIf8mMKQ8bsCFbA7MgodK1kA4Q

 

[JayD]

Hydroponics grow stores have the same thing as kaowool, They call it {Rockwool} you can buy it in 6"x 6"x 6" cubes or slabs that you can cut it with a sharp bread knife. . Pretty cheap too. 100% same stuff

 

[etiger2007]

I have Roxul insulating the back and sides of my insert, approved by SBI. I noticed my coals last alot longer than without the insulation. I didnt sheet metal anything , just cut the insulation to size and place between insert and fireplace walls. I have no issues with the Roxul fibers getting into the house, its obviously behind the surround.

 

[mellow]

Pickup some half inch Durock, that and Roxul will help keep the heat in and you can find it at Lowes.

 

[jatoxico]

Pickup some half inch Durock, that and Roxul will help keep the heat in and you can find it at Lowes.

Thanks for all the replies. Mellow I believe I read your thread about insulating the firebox and thought you concluded it did not make any difference, am I mistaken about that? Just in regard to burn time?

I have Roxul insulating the back and sides of my insert,

Did you run w/o it or was it installed that way? Was there a noticeable difference? Just trying to figure what if anything will work.

I think you'll get more bang for the buck with the blockoff plate

In reading old posts and recommendations people always seem to feel the block off was worthwhile so perhaps if you had to pick one, reflecting with metal is more effective than insulation?? IDK if I even have room for insulation but can always slide a sheet of metal in there.

 

[EatenByLimestone]

In reading old posts and recommendations people always seem to feel the block off was worthwhile so perhaps if you had to pick one, reflecting with metal is more effective than insulation?? IDK if I even have room for insulation but can always slide a sheet of metal in there.

Well I'm insulated top and bottom so not convinced the block off will help my issue, maybe it will IDK. I know Lowe's carries sheet metal is kaowool available at HD or Lowe's?

I think the metal plate will be enough of an addition to the chimney. If you can put a blanket of insulation along the back that can't hurt. If you can only fit a sheet of Durock back there, that will help some as it does have an R value. I'm a big supporter of radiant/reflective barriers in the right applications. If there is space for the heat to be reflected back, they will help. They won't help if there isn't any space to reflect the heat back into.

 

[mellow]

I found that with Roxul alone I was losing heat to the outside brick in the back and top, with the addition of half inch Durock I have stopped that heat loss, I was measuring 60 degree temps on my outside brick on 30 degree days before adding the Durock, now it is the same as the air temperature.

For me personally I would rather mess with concrete board than metal, but each to their own.

 

[jatoxico]

I found that with Roxul alone I was losing heat to the outside brick in the back and top, with the addition of half inch Durock I have stopped that heat loss, I was measuring 60 degree temps on my outside brick on 30 degree days before adding the Durock, now it is the same as the air temperature.

For me personally I would rather mess with concrete board than metal, but each to their own.

Thanks EBL. Hey Mellow how about 80on a 30 day? Measured that about week and half ago or so. I need a clear plan because I can't be taking that thing in and out. I'm not an installer and that's a heavy insert.

 

[mellow]

The 450 is heavy, I can only imagine moving the 550 around. I would definitely have someone there to help if you are going to pull it out. If your game plan is to just toss Roxul all around it then you shouldn't need to pull it out much depending on how tight of a fit it is.

 

[drewberry24]

So to insulate the stove or firebox, you put Roxul and or Durock around the insert inside the masonry fireplace? That sounds pretty easy and nearly hassle free. The first floor part of my chimney backs up to the laundry room, so it is not exposed and it gets comfortably warm in there. The second floor part of the chimney is outside, about 10-15 feet. I do not have a block off plate so I wonder if this is something I should do. After a discussion with Mellow on here yesterday and reading this post I am considering it.

 

[etiger2007]

Thanks for all the replies. Mellow I believe I read your thread about insulating the firebox and thought you concluded it did not make any difference, am I mistaken about that? Just in regard to burn time?



Did you run w/o it or was it installed that way? Was there a noticeable difference? Just trying to figure what if anything will work.



In reading old posts and recommendations people always seem to feel the block off was worthwhile so perhaps if you had to pick one, reflecting with metal is more effective than insulation?? IDK if I even have room for insulation but can always slide a sheet of metal in there.

I started out running with out it, Yes the stove does stay warmer longer, and the coals stick around longer.

 

[jatoxico]

Went to see the dealer about having them fix an issue I have wanted them to resolve for a while. I explained the situation and the owner is supposed to call me back.

My hope is to have the materials I need on site, let them pull the stove and then add the block and do some type of insulating to the firebox. before they reinstall. I'll have to pull the surround to see what my options are.

 

[jatoxico]

Has anyone tried Rock Board (roxul product) as an insulator? Don't have much room in the firebox back and sides for regular 3 1/2" roxul batting.

 

[begreen]

Sounds like it would work.