Rock wool as insulator?

[Lburou]

from Wikipedia Mineral wool, mineral fibres or man-made mineral fibres are fibres made from natural or synthetic minerals or metal oxides. The latter term is generally used to refer solely to synthetic materials including fibreglass, ceramic fibres and rock or stone wool. Industrial applications of mineral wool include thermal insulation, filtration, soundproofing, and germination of seedlings.

Rock wool is made from rocks here in Texas, so should be plentiful and cheap. Has anyone used this material to insulate above their dome? I would consider it under a roof above the dome.

[Lburou]

Re: Rock wool as insulator?

see This thread for more

[SCChris]

Re: Rock wool as insulator?

I used 2 inch boards as the insulator directly in contact with the dome. As I have stated in other places, the board product isn't as flexable as I would have liked. I was looking for the bats I used in the 70s, these were more like fiberglass bats. My opinion is that cost wise the ideal would be to find rockwool blankets, if they exist. I'm envious of the ceramic blanket, these look so taylored when in place compaired to the rockwool boards. In an enclosure, I don't know that Ceramic Fiber or Stonewool, rockwool, will really perform very different if care is taken when placing the insulation. I wrapped and tucked scraps in open spaces and outside of the direct contact with the dome I placed Fiberglass in the enclosure corners, for support of the stonewool and for convenience sake. After getting these tight and tidy I poured vermiculite over the top of this and filled out the enclosure. I'm happy with how things turned out. I think I loose more through the floor and slab than through the dome. On top of the 5" inch slab I have 2" inches of rigid ceramic insulation on top and then the 2.5" firebrick and dome laying on this insulation.

Chris

[Lburou]

Re: Rock wool as insulator?

Sounds like you attended to the little details. Can you tell us how long it takes to heat your oven to pizza cooking temperature and how long it stays hot?

[SCChris]

Re: Rock wool as insulator?

Heating an oven is a bit variable, how big was the fire and how fast it got there.
How log it stays hot is a function of how log the burn was and how saturated the oven gets. Most times I go slower in the beginning and build after the first half hour or so, but the dome usually goes white in about 1.5 hours. I can never tell just when company is going to be ready so most burns go for several hours, 3 to 5.

My oven is perceptably above ambient at 5 days. Typically I run about 725 +- on the deck when I close the door. The next day I drop about 150F or so, say 475 - 500, the following day about 350 or so and about 270 or so on the forth night. So cooking goes something like this.

1st night Pizza
2nd - High heat Roast - eg. lamb rib roast, or boneless leg of lamb and roast veggies
3rd - Hash of the previous night
4th day long Sholder Roast of pork -
Once the food is out the next starter load of wood goes in to dry.

Chris

[Lburou]

Re: Rock wool as insulator?

Heating an oven is a bit variable, how big was the fire and how fast it got there.
How log it stays hot is a function of how log the burn was and how saturated the oven gets. Most times I go slower in the beginning and build after the first half hour or so, but the dome usually goes white in about 1.5 hours. I can never tell just when company is going to be ready so most burns go for several hours, 3 to 5.

My oven is perceptably above ambient at 5 days. Typically I run about 725 +- on the deck when I close the door. The next day I drop about 150F or so, say 475 - 500, the following day about 350 or so and about 270 or so on the forth night. So cooking goes something like this.

1st night Pizza
2nd - High heat Roast - eg. lamb chops or boneless leg of lamb and roast veggies
3rd - Hash of the previous night
4th day long Sholder Roast of pork -
Once the food is out the next starter load of wood goes in to dry.

Chris

Thanks Chris for a simple explanation describing your heating curve....Very useful for this newbie

[SCChris]

Re: Rock wool as insulator?

Somehow I got lamb chops down where I meant to say "lamb rib roast". A lamb loin roast is also a great choice for night 2. heat a cast iron skillet in the oven, season the little beasty and drop it in the skillet. My choice is rare to medium rare.

Chris

[Lburou]

Re: Rock wool as insulator?

Somehow I got lamb chops down where I meant to say "lamb rib roast". A lamb loin roast is also a great choice for night 2. heat a cast iron skillet in the oven, season the little beasty and drop it in the skillet. My choice is rare to medium rare.

Chris

Even so, your post has as much information in it as an announcer reading the small print at the end of a commercial, thanks for taking the time

I'd like to know more about the details of your oven....Did you build extra mass to keepthe heat that long? What kind of floor and floor insulation did you use?

[SCChris]

Re: Rock wool as insulator?

Lburou,
I didn't add any additional mass to my oven than is indicated in the standard FB plans. The insulation on the other hand, I did take a bit more care.

I used 2" inches of Ceramic Fiber board under the oven and used an enclosure around the dome that I filled with insulation. I think I have 8 to 10 inches of insulation directly over the oven, most of this is stone wool. At the base of the oven is about 4 inches and in the corner of the enclosure is fiberglass attic insulation.

The Fiberglass insulation was convienent and available at lowes but the cost was about what I would have paid for stone wool. The door is made from some of the remaining rigid ceramic board insulation, this could be improved with some "oven door gasket" and I intend to do this at some point.


Chris

[Lburou]

Re: Rock wool as insulator?

Lburou,
I didn't add any additional mass to my oven than is indicated in the standard FB plans. The insulation on the other hand, I did take a bit more care.

I used 2" inches of Ceramic Fiber board under the oven and used an enclosure around the dome that I filled with insulation. I think I have 8 to 10 inches of insulation directly over the oven, most of this is stone wool. At the base of the oven is about 4 inches and in the corner of the enclosure is fiberglass attic insulation.

The Fiberglass insulation was convienent and available at lowes but the cost was about what I would have paid for stone wool. The door is made from some of the remaining rigid ceramic board insulation, this could be improved with some "oven door gasket" and I intend to do this at some point.


Chris

Thank you Chris! Do I assume correctly that you put the firebrick on the oven floor (larger side down for 2.5 inch thicck floor) and half-bricks for the dome? The extended baking time must be the result of the more than adequate insulating job you have done with the rock wool, yes?

[SCChris]

Re: Rock wool as insulator?

Lburou, you are correct with regard to how the floor is set.

I have done a bit of tweaking in the landing area. Initially I built to the exact FB plans; next I replaced the entry with a single slab of soapstone and I found that what I created was a conduit for the heat to flow into the entry, not good. I tweaked things by pulling the entry soapstone forward and adding back a 2” bit of firebrick, things got better. I found that the heat retention returned to what it had been before the entry change. Next I added a profiled slice, a heat break, of rigid ceramic fiber board between the oven floor and the stone in the entry, the soapstone was replaced with granite. The results of this change are that the heat retention was even better.

The transition from the oven into the entry and from the oven into the flue, are most often not insulated and therefore an area that caries heat from the oven. Some here are working on or have built a material break into these areas to retain more heat in the oven. I feel that you can choose to bleed off heat when you need to, so I’d rather have more insulation than less around the oven.

As far as materials; a feature of the soapstone is heat conductivity. This is great for something’s and not so good for others. A good example is pizza stone or the oven floor in a pizza oven. A warning here, the bread baking community using Alan Scott designed ovens, don't feel that soapstone is idea for bread. These ovens have roughly twice the thermal mass than the FB style ovens, my guess.

I feel the the FB design is more flexable with regard to usage. I have though about increasing the thickness of the floor to bring up the thermal mass, but this is more about my curiosity about how the heat curve of the oven will change than a real expectation that this change would benifit my cooking. If I were more dedicated to large bouts of bread baking, then the additional mass would matter. As it is, my 43 inch oven would like to have something like 16 lbs of bread baked at once. The additional mass would come into play on the second and later batches of bread. That's a whole bunch of bread to makeup.. The other aspect of mass is that it will take more time to heat up and so also take more wood.

The firebrick is less conductive than the soapstone and the rigid board insulation is almost a factor of 10 less conductive than the brick.

The advantage of the single surface in the entry area is cleanups are a snap. Inside the oven the firebrick is self cleaning but in the entry spills become a part of the firebrick because of the porous nature of the brick. It also allowed me to make the entry area consistent with the outside work surfaces.

Chris

[Lburou]

Re: Rock wool as insulator?

Again Chris, you have aided my understanding of this complicated process..Thank you a thousand times for taking the time to share your experience with a newbie

I have moderated several forums on a very busy message board for ten years, and I know that through the years I've grown calloused to the needs of newbies (look for Leeburough -Turbobuick.com forums). I'll have to go back to helping those new people find/discover the same information and processes over and over again, thanks for renewing my commitment to helping the newbies

[Lburou]

Re: Rock wool as insulator?

Mineral wool is the name in Europe for what we call fiberglass insulation, and it has the same problem: organic binders that burn and stink. Make sure what you buy is meant for refractory applications and will withstand 1000f temperatures.

Chris, note the quote above. Its a caution by dmun from another thread about 'mineral wool' not rock wool. Nevertheless, did you notice any of these issues when you fired up your oven with a major amount of rock wool supplementing the ceramic insulation?

[SCChris]

Re: Rock wool as insulator?

I didn't have any negative experience with regard to rock wool/mineral wool, smell or otherwise. Wikipedia indicates that mineral wool is the correct term.

Mineral wool - Wikipedia, the free encyclopedia

This article does indicate "Mineral wool may contain a binder, often food grade starch, and an oil to reduce dusting."


Chris

[Lburou]

Re: Rock wool as insulator?

Found this quote in another thread, but its pertinant here:

tfasz,

My oven is reasonably small and is not an igloo - it's enclosed. But my insulation worked out significantly cheaper than that:

- A 25 sq ft roll of insulation easily covered my dome/arch once, with enough to cover the top twice.
- Insulation is "Tombo" brand rockwool, made in Indonesia. It has an operating temp of 650c (1200F)
- 2" thick roll, so my dome top has 4 inches over it

The whole roll cost me about $50 from an industrial insulation guy - not sure if it's available where you are, but it works really well and was a great price.