Required density of fiberboard insulation

[WJW]

Hello All,

Been lurking for a while but this is my first post. The amount of information here is amazing. Hats off to those responsible.

I'm in the process of trying to source local materials and have hung up on the insulation. I'd prefer to use fiber board over vermiculite for performance and compactness. That being said I'm finding the various fiberboard materials to be relatively pricey. Still leaning toward the fiberboard but I'm unclear as to what properties are required. I've come across two inch thick sheets rated to 2300F at densities ranging from 16 to 24 lbs per cubic foot. The prices vary significantly. Any thoughts on what is required? What does increased density get me? Resistance to compression?

Also, do I need board rated to 2300? Is 1800 degrees enough? I'm seeing boards rated to 1800 with a 19lb density which are 47"x39"x2" for $116. Same size and density with a temp rating of 2300 goes for $157. Is the extra temp rating worth the extra money?

Are there other sothern california sources out there anyone is aware of?

I've read that the FB store carries these supplies (and have seen the kits) but I don't see Fiberboard and blanket separately listed???

Bill

[Dino69]

Re: Required density of fiberboard insulation

WJW,

They are in the store under "Installation Accessories." You could probably drive to get them. If I remember correctly the board is $70 per sheet and a roll of blanket is $75. I have shopped around a bunch and James has really good prices.

Good luck.

David...

[WJW]

Re: Required density of fiberboard insulation

Thanks Dave.

I don't know why I couldn't find them previously. It's the proverbial situation of had they been any more obvious they'd have bitten me.

Bill

[GianniFocaccia]

Re: Required density of fiberboard insulation

Bill,

I have never used these guys, but there is a place right down the freeway from you in North Hollywood called McGills Warehouse that carries refractory products. I understand this is a true warehouse (with minimal-to-no customer service) that caters to professionals and has a $50 minimum.

McGills Warehouse Online Department Store,HF102 2" Ceramic Fiber Boards Density: 17.5lb/ft3 or 280kg/m3

John

[WJW]

Re: Required density of fiberboard insulation

Thanks John. I already ordered Insboard 19 from the ANH (Harbison Walker) over in Santa Fe Springs (down your way). I had been planning to go to San Diego for a golf weekend on Friday and was going to stop by there and pick it up from "will call" on my way down. As it turned out with the rain and some other comittments things got pushed back to Saturday. Since ANH isn't open Saturday I had them ship it to me instead. Shipping was $64 and the stuff is going to arrive tomorrow.

I bought two cartons of three inch thick Insboard19. There is fifteen sqaure feet per carton. The sheets are 36 inches by 12 inches, and there are five sheets per carton. For some reason (??) the three inch thick sheets were ten dollars cheaper per carton than the two inch thick sheets! In any event, the three inch thick Insboard was $95.48 per carton. With two cartons (30 square feet) I'm going to have quite a bit left over, but I figure I could make a door, sell some on Craifg's list, or whatever.

I know it's the minority position around here, but I've decided to go with a barrel vault style with interior dimensions measuring roughly 36 inches wide by 42 inches long. I chose that style for ease and speed of build and am going to try to keep thermal mass as low as possible to aid in heating times.

I'm laying the firebricks flat on the floor, on their edge on the side and back, and full thickness in the vault. As such, the floor, sides, and back will be 2.5 inches thick firebrick, and the vault roof will be four and a half inches thick firebrick. I'm going to keep side and roof cladding to no more than two inches. (I'm planning to reinforce the side cladding with copious amounts of chicken wire to take the side-load being stransmitted to the sidewalls from the arch.)

I figure that plan is going to give me thermal mass comparable to a similarly sized pompeii style but with a significantly easier build. With all the insulation I figure I should have a pretty efficient oven, but we'll see.

Since I will have sidewalls which are flat and vertical for about 9 nine inches high, I can use left over Insboard to insulate that portion of the sidewalls as well as the rear wall of the oven.

I also bought two 25 sguare foot rolls of one inch thick Inswool blanket for $124 per blanket. All in, it's about four hundred dollars for all the insulation but I should be able to really well insulate with what I have.

If anyone has any thoughts or critique on the plan or Inswool products, I'm all ears. I'd also like to hear thoughts on the realative efficiency of what I have in mind.

Thanks again for the input.

Bill

[GianniFocaccia]

Re: Required density of fiberboard insulation

Hey Bill,

I have to give a thumbs up for the Insboard 19 since that is what I bought from Frank at ANH in SFS too. Whatever you have left over, please let me know. My brother lives in Camarillo (behind the Von's at Mission Oaks/Woodcreek) and is slowly collecting materials for a 36# pompeii. I'm envious that you're going with 3" (I went with 2" on top of 3.5" of vermicrete).

You won't be unhappy with the barrel vault. If I could recommend just one thing, though, it would be to lay your side/rear bricks flat to get a uniform thickness of 4.5" all the way around. I believe this would not only add to the strength/stability of your oven, it would also contribute to a more even heat sink/distribution. The sideways thrust of your vault on a thin wall (pier) is significant, with a capital S. Given what you've already invested in proper insulation, it would round out your design.

I know it's common to lay barrel vault floor bricks on their side for added floor mass, but unless you plan on doing mutiple batches of bread, I'm not sure it's necessary. You're already ahead by not slipping a layer of concrete between your floor and the support slab, as called for in Alan Scott's design.

If you have any other questions you would like to bounce off me, please feel free. I don't get to visit my brother that often, but if it's convenient, would love to stop by and see how you're progreessing, maybe even help out a few hours since I'm growing impatient waiting for my other brother Darrell (ha) to build me a stainless entryway floor and flue.

Don't forget to take tons of pics.

John

[brickie in oz]

Re: Required density of fiberboard insulation

What John said.
I would/did make the side walls the same as the roof thickness, with plenty of insulation like you suggest and you will have a great oven.

[WJW]

Re: Required density of fiberboard insulation

John and Al:

Thanks for the input.

Anytime you're in town John (you too, Al, but your's is a bit longer trip.), feel free to give me a call. I'd love to have you by to take a look at what I've got going. I'm at the western end of Camarillo in the little hills above Sterling Hills golf course.

Here are some pics of what I have so far.

These are the location in the backyard. Decided to go go to the left of the gazebo. Still relatively close to the pool area but good kitchen access as well.


Here's some progress on the stand









Since the last pic I've finshed the stand and pulled the forms. It's ready for the insulation.

Bill

[flyfisherx]

Re: Required density of fiberboard insulation

I already ordered Insboard 19 from the ANH (Harbison Walker)Bill

I just went out to their web site. I am on the east coast. How did you order the Insboard 19 ? I do not see any way to place an order other than calling them up. Up to now, all suppliers I have contacted do not sell to the general public.

Thanks

[WJW]

Re: Required density of fiberboard insulation

I called them up and placed the order with a credit card. Spoke to the Santa Fe Springs, CA location. To save on shiping you'd obviously want to call a location near you. (One thing to keep in mind is that while the insboard19 seems to be a good deal, the FB blanket you can order here seems to be significantly less expensive. I didn't realize that until after I'd placed the order. )

They asked me what company I was with and I told them I was an individual but if the pricing would be significantly lower I'd have my brother (an airconditioning contractor) give them a call and place the order. She said she'd give me a good price and not to bother.

Gotta love the sporting names around here. We've got a fly fisherman and a sharptail hunter. Two activities near and dear to my heart.

Bill


P.S.: Hey John and Al ...if you're reading...why can't I clad with reinforced concrete to take up those loads? I moved my discussion of this issue over to the "Other Oven Types" board where it probably belongs. Thanks.

[GianniFocaccia]

Re: Required density of fiberboard insulation

Bill,
You can clad with reinforced concrete. It is not recommended because Portland cement breaks down over time from thermal cycling and is not a long-term solution. I also think full firebricks would provide thermal consistency (both heat up and radiation) as well as structural integrity.

Maybe someone else has a different view?

[brickie in oz]

Re: Required density of fiberboard insulation

why can't I clad with reinforced concrete to take up those loads?

If you insulate between the fire brick and concrete I cant see a problem, I wouldnt put the concrete hard up against the fire brick Alan Scott style as it creates too much thermal mass and takes too much fuel and time to heat up.

[david s]

Re: Required density of fiberboard insulation

Bill,
You can clad with 50%portland and 50% lime in the mix. Also for a barrel vault your end walls should be inside the vault not outside.

[WJW]

Re: Required density of fiberboard insulation

Sorry for the newbie questions...

So are you guys suggesting I skip the cladding altogether and just go with the insulation up against the brick. (I'm trying to keep my mass down, but concrete is mass as well. If I can skip the concrete then there's little net increase by using the full thickness firebrick?) If that's the case then I can see why you'd say to use the brick laying on it's flat side.

I also need to apologize for using the wrong terms. When I said "concrete" I really meant that I was going to use a mortar mixture with fireclay added. I was assuming (maybe incorrectly) that I could apply that over a rebar or heavy chicken wire cage and that would work and take up the sheer load. If you guys think I'm wrong on that count please let me know.

Got my insulation...

[azatty]

Re: Required density of fiberboard insulation

McGills carries a few high temperature products, including the ceramic blanket in 1-inch (HF11) and 2-inch (HF-12) thickness. If you're local to them, it's cheaper that FB blanket and has identical specs. Their online ordering system used to be a total mess, but they cleaned it up. But as a walk-in, you'll be fine and won't get your credit card charged six times when the online system won't process it correctly (happened to me). Customer service ain't Forno Bravo style, but they're still ok. Just don't expect them to be as patient with newbie questions and "will this work for me" questions.

Bill,

I have never used these guys, but there is a place right down the freeway from you in North Hollywood called McGills Warehouse that carries refractory products. I understand this is a true warehouse (with minimal-to-no customer service) that caters to professionals and has a $50 minimum.

McGills Warehouse Online Department Store,HF102 2" Ceramic Fiber Boards Density: 17.5lb/ft3 or 280kg/m3

John