Mineral Wool/RockWool

[stonecutter]

Re: Mineral Wool/RockWool

Yes, I think the entry is the main problem area, although I'm also sure the porous refractory picks up moisture from the air in very humid weather (for those oven owners in the tropics), especially if the oven is not getting much use at this time of year, even if the oven doesn't get wet. I've seen lots of igloo style ovens, including those commercially available, that do not have any seal between the flue and the outer shell. Any water hitting the flue pipe will simply run down the pipe and into the entry area, then spread throughout the oven via the porous refractory and if any excess, will just settle under the floor. Another problem area in an igloo style oven can be where the outer shell meets the supporting slab, for an igloo style oven. With plenty of use after a couple of years a crack sometimes develops here and water entry at this point can occur. If the oven has not been built with a slight slope downwards on the supporting slab towards the perimeter then water entry here into the under floor insulation can be a problem.

No argument here, brick and stone will absolutely absorb moisture from atmospheric surroundings. If we had tropical conditions here, I would have a removable outer door with a weather seal on it. As far as the chimney, I have idea on how to weather seal that too...it would have to be a double insulated boot.

I think the easiest problem to solve is your cold joint between the outer shell and structural slab. A flexible flashing membrane can be installed over the insulation, lapped at least 3" on the seams and minimum 3" up the side of the oven. Also, the membrane should be inserted into the structural slab by cutting a 1" deep slot around the perimeter, and caulked after tucking in the membrane. When the stucco is applied, it would hide the flashing.

[david s]

Re: Mineral Wool/RockWool

Arizona is far from tropical.

Here in SC we are subtropical, do I know what you mean. What areas of the oven get moisture intrusion? The entry would be the only obvious area, everywhere else should not get much, if it's built properly

Yes, I think the entry is the main problem area, although I'm also sure the porous refractory picks up moisture from the air in very humid weather (for those oven owners in the tropics), especially if the oven is not getting much use at this time of year, even if the oven doesn't get wet. I've seen lots of igloo style ovens, including those commercially available, that do not have any seal between the flue and the outer shell. Any water hitting the flue pipe will simply run down the pipe and into the entry area, then spread throughout the oven via the porous refractory and if any excess, will just settle under the floor. Another problem area in an igloo style oven can be where the outer shell meets the supporting slab, for an igloo style oven. With plenty of use after a couple of years a crack sometimes develops here and water entry at this point can occur. If the oven has not been built with a slight slope downwards on the supporting slab towards the perimeter then water entry here into the under floor insulation can be a problem.

[stonecutter]

Re: Mineral Wool/RockWool

Arizona is far from tropical.

Here in SC we are subtropical, do I know what you mean. What areas of the oven get moisture intrusion? The entry would be the only obvious area, everywhere else should not get much, if it's built properly

[david s]

Re: Mineral Wool/RockWool

True, mineral wool is more prone to water absorption. But if your insulation is absorbing water, then the problem isn't the insulation...you have a weather proofing problem.

In other words, if you dry out, then dry in the oven properly, water absorbtion isn't a factor.

If you live in the tropics, for certain times of the year everyone has a weather proofing problem. Sometimes in really humid weather clothes will go mouldy in the wardrobe.

[stonecutter]

Re: Mineral Wool/RockWool

I've found the main difference is that the rock wool is far more water absorbent than ceramic fibre- a disadvantage. The ceramic fibre cuts and bends better- advantage. You just need to weigh this up with the price difference and availability.

True, mineral wool is more prone to water absorption. But if your insulation is absorbing water, then the problem isn't the insulation...you have a weather proofing problem.

In other words, if you dry out, then dry in the oven properly, water absorbtion isn't a factor.

[azpizzanut]

Re: Mineral Wool/RockWool

Hi All,

Wow, it's been a long time since my last post.

Mineral wool is an alternative to consider for insulating an oven. I have two ovens and one is insulated with mineral wool. Why did I consider mineral wool? It was cheaper than ceramic fiber blankets, available locally, and did a good job. I had no problem cutting and fitting the pieces to fit the shape of the dome. If you have ceramic blanket easily available then by all means use it. I found it expensive.....this fact is not a consideration for some. I don't begrudge them their financial status or ability to obtain the finest and latest state of art products for their oven project. Consider though, the products that insulate ancient ovens...successful ovens, of the past. Mineral wool works and so does other types of insulation including wood ash, perlite, vermiculite and others.

The important thing is to insulate your oven well. Both of my ovens have 4 inches of either perlite or vermiculate over the dome. The dome is covered with mineral wool on one and ceramic fiber on the other. Imagine a box with an internal dome (covered with mineral wool or ceramic fiber) and that is covered with loose fill of perlite or vermiculite. That's my ovens. With all of that, does it really matter what I used to cover the brick dome (ceramic blanket or mineral wool)? Some will say maybe it does, but my ovens will still be hot three days later if I cover the door opening (mineral wool or hi-tech ceramic) be darned. Use what is available and what you can afford. Be confident that what you use is adequate and make changes later on your second oven, or third, or other. Golly, you should see what passes for a pizza oven around here and they all seem to cook adequate pizza. Dont' stress over it.

Cheers,

Bob

[david s]

Re: Mineral Wool/RockWool

I've found the main difference is that the rock wool is far more water absorbent than ceramic fibre- a disadvantage. The ceramic fibre cuts and bends better- advantage. You just need to weigh this up with the price difference and availability.

[stonecutter]

Re: Mineral Wool/RockWool

I do. It's not on par in for inch with ceramic, but it does a great job, is easy to find and is very cheap. In tandem with loose fill insulation like perlite or vermiculite I see zero difference between the ovens I insulated with mineral wool vs the ceramic.

[Jimney]

Re: Mineral Wool/RockWool

Are people using this in place of the ceramic fiber blankets right on the brick dome?

[Lburou]

Re: Mineral Wool/RockWool

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.

[SCChris]

Re: Mineral Wool/RockWool

The binders are the reason fiberglass insulation is a no-no, I personally have a hard time seeing that the actual glass would melt at the temps that we get on the outside of the dome but the binders used in fiberglass won’t add to love of the oven.

I don't know if stone wool ever has binders added, but I checked to verify that what I was getting didn't have them before I purchased and installed my boards. I haven't experienced any disappointment with the stone wool boards other than their limited flexibility.

I wrapped the boards into place and stuffed little bits into gaps and in the end I poured vermiculite into the enclosure and around the stone wool covering the dome and thus providing even more insulation.

As I have said elsewhere, the ceramic blanket is far superior when compared to the stone wool boards when tailoring the materials to the dome shape, but with just a bit of care the stone wool will do a very fine job of insulating. Stone wool is likley to be more available in many locations than is the ceramic blanket.

Chris

[dmun]

Re: Mineral Wool/RockWool

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.

[Lburou]

Re: Mineral Wool/RockWool

I was looking around and found that the R-Values of the fiberglass and the Rock Wool are about the same, with the Fiberglass being a bit higher per inch. 0.5 at most

The main difference between the two is the melting point with fiberglass melting at a considerably lower temp and ceramic having a much higher melting point.

Material Temperature
Glass wool 230 - 250 ?C (445-480 F)
Stone wool 700 - 850 ?C (1290-1560 F)
Ceramic fibre wool 1200 ?C (2190 F)

Important and timely information Storm Runner! Thanks for the leg work on this.

With a one inch ceramic layer over the dome, the rock wool would make a good filler instead of vermiculite then, right?

[azpizzanut]

Re: Mineral Wool/RockWool

Hello All,

The mineral wool I got was in batts 4" thick. It was somewhat flexible but firm. I was able to split it into layers when I needed thin "sheets" and then saw full sized batts with a regular crosscut hand saw for odd shapes. One manufacturer packaged it in a bundle of four and another in a bundle of five. It is often used as fire block in buildings so it is sized for placement between studs. It is also used as a sound dampener.

Cheers,

Bob

[C5dad]

Re: Mineral Wool/RockWool

I have nto seen it in the loose form, though if you get ahold of the company mining and processing it, I bet you could get it as loose fill!