Mineral Wool/RockWool

[azpizzanut]

Hello All,

It was hard to find, but I finally found mineral wool batts in a variety of thicknesses. It is available from an insulation contractor in Phoenix, Arizona. It comes in 4lb and 8lb density. I plan to use the 2" thick batts since it will be easier to form over the igloo dome, I'll use two layers. That should allow me to smooth out lumps before covering with chicken wire mesh. I take it from comments made on the forum that the 8 lb density is the best choice. Correct?

The oven manufacturer recommends a layer of insulating refractory concrete over the precast oven panels. They supplied four bags with the kit. I want to cover the insulating concrete with 4" mineral wool then a layer of vermiculite concrete mix. Then a layer of stucco, then paint as a weatherproof barrier. Is this sequence reasonable? Any recommendations before I begin casting insulating concrete for the hearth firebricks? Construction should go fast after the hearth is laid since the oven panels are precast in sections.

By the way, I contacted the oven manufacturer with questions on finishing the oven beyond the initial layer of insulating refractory concrete and was informed that the company is in the business of casting the parts and wouldn't recommend a finishing sequence. "Contact a mason". I've already exceeded my oven budget so won't be hiring a mason. I hope to get some ideas from forum members.

Cheers,

[C5dad]

Re: Mineral Wool/RockWool

Hey azpizzanut - which contractor has the mineral wool? my normal supplier dried up.

CW

[azpizzanut]

Re: Mineral Wool/RockWool

Border Construction specialties.

[SCChris]

Re: Mineral Wool/RockWool

The lower density, 4lb, should provide a greater R-Value but less support for the Vermicrete. I tried to look up the R-Value difference, but didn't imediately find it. Your vendor will be able to tell you this. The lower density should also be a bit easier to form, less material, more air, it should more flexable everything being the same.



Chris

PS I've rooted around the net and don't find Density / R-Values. Ask your evndor and please let us know what you find. Thanks!

[azpizzanut]

Re: Mineral Wool/RockWool

Thank you, SCChris.

Less support? Yes, I see your point. Maybe use a heavier 2" chicken wire mesh or possibly a 1" chicken wire and two layers of rock wool, each held with the wire. I don't mind doing the extra work. Is there something other than hexagonal wire to hold rock wool?

I was able to find R value information for rock wool vs fiberglass. They are about the same except rock wool ,being denser per cu ft, is the better barrier to sound. One site gave the value of 2.5lb density rock wool as R-3.7 per inch thickness and R-3.9 per inch for 4lb density. If we extrapolate, then the 8lb density would have even higher R value, though not twice that of 4lb.

Only one manufacturer uses a liquid ablative to coat their rock wool product. The others do not, according to a website. I've learned a lot about rock wool in the past ten minutes thanks to Google.

Cheers,

[SCChris]

Re: Mineral Wool/RockWool

I don't know that support for the vermicrete would be a problem at all. Many of those making igloo style ovens are running the vermicrete right over the ceramic fiber blankets and this would have much less support for this layer. Best to you!

Chris

[Storm Runner]

Re: Mineral Wool/RockWool

Thank you, SCChris.

I was able to find R value information for rock wool vs fiberglass. They are about the same except rock wool ,being denser per cu ft, is the better barrier to sound. One site gave the value of 2.5lb density rock wool as R-3.7 per inch thickness and R-3.9 per inch for 4lb density. If we extrapolate, then the 8lb density would have even higher R value, though not twice that of 4lb.

Cheers,

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)

[C5dad]

Re: Mineral Wool/RockWool

Nice thing about the vermicrete is that it is fairly light, so should not compress the insulation unless you press down.

[Lburou]

Re: Mineral Wool/RockWool

When I was young rock wool was available as loose fill, much like vermiculite is today. Is it still available in that form today? In that form, it should be easily adaptable to our WFO projects.

[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!

[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

[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?

[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.

[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

[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.