Help Interpret this Response from the Rockwool People

[Vernation]

Hi There,
I was searching on the forum for insulation options and learned about Rockwool.


I thought: Here is the perfect thing! It doesn't hold water, has a good R value, and (hopefully) won't degrade with time (as I'm worried the foam products might do).


I wrote to Rockwool asking for their suggestion as to which of their products would be best for a vintage Airstream.


Here is their response:


With regards to your e-mail, our products can, in theory, be used to insulate a camper/trailer/van. However, we do not have tested assemblies to give you results on.
Our products are fibrous and made from mineral wool. This creates a vapor permeable product which is non-combustible.

Because the product if vapor permeable, a vapor barrier may be required to prevent condensation occurring within it during the colder months.
What this relates to is the dew point. Even with a vapor barrier, condensation can occur if it is too thin, extremely cold outside, and warm and moist inside.

The batt product would be recommended as a friction fit between stud framing

It may be easier to consider AFB® It runs from a 1” through to 4” thickness in 1/2” increments as well as a 5" and 6" option
https://p-cdn.rockwool.com/siteassets/o2-rockwool/documentation/technical-data-sheets/commercial/afb-acoustical-fire-batts-techdata.pdf

I hope this information helps. Feel free to contact me with any other questions you may have.





So now I'm thoroughly confused: I thought permeability was a plus because moisture won't be absorbed. Won't condensation happen no matter what insulation you use because the walls are so thin?


Can someone explain the finer points of insulation that I am missing?

[Jcondon]

Originally Posted by Vernation

Hi There,
I was searching on the forum for insulation options and learned about Rockwool.


I thought: Here is the perfect thing! It doesn't hold water, has a good R value, and (hopefully) won't degrade with time (as I'm worried the foam products might do).


I wrote to Rockwool asking for their suggestion as to which of their products would be best for a vintage Airstream.


Here is their response:


With regards to your e-mail, our products can, in theory, be used to insulate a camper/trailer/van. However, we do not have tested assemblies to give you results on.
Our products are fibrous and made from mineral wool. This creates a vapor permeable product which is non-combustible.

Because the product if vapor permeable, a vapor barrier may be required to prevent condensation occurring within it during the colder months.
What this relates to is the dew point. Even with a vapor barrier, condensation can occur if it is too thin, extremely cold outside, and warm and moist inside.

The batt product would be recommended as a friction fit between stud framing

It may be easier to consider AFB® It runs from a 1” through to 4” thickness in 1/2” increments as well as a 5" and 6" option
https://p-cdn.rockwool.com/siteassets/o2-rockwool/documentation/technical-data-sheets/commercial/afb-acoustical-fire-batts-techdata.pdf

I hope this information helps. Feel free to contact me with any other questions you may have.





So now I'm thoroughly confused: I thought permeability was a plus because moisture won't be absorbed. Won't condensation happen no matter what insulation you use because the walls are so thin?


Can someone explain the finer points of insulation that I am missing?

The inside skin is an almost perfect vapor barrier. Rock wool is no different than fiberglass in that regard. They are recommending the higher density board to eliminate the chance of partially collapsing inside the wall. The high density stuff is rigid enough to support itself.

[richard5933]

Are they concerned that condensation might form on the inner side of the interior skin and get on the insulation? That would be about the only thing a vapor barrier on the insulation would help from what I can see. Or are they possibly concerned about interior moisture getting through the interior skins and getting into the insulation?

[Jcondon]

Originally Posted by richard5933

Are they concerned that condensation might form on the inner side of the interior skin and get on the insulation? That would be about the only thing a vapor barrier on the insulation would help from what I can see. Or are they possibly concerned about interior moisture getting through the interior skins and getting into the insulation?

They don’t totally understand the application. Airstreams with the inner aluminum skin intact has an excellent vapor barrier both inside and out. If the inner skin is replaced with T&G wood or another permeable material then a good vapor barrier should be included for sure. Condensation will occur inside the wall if the water vapor can get into the cavity.

[TeddyK]

This 👍

Originally Posted by Jcondon

They don’t totally understand the application. Airstreams with the inner aluminum skin intact has an excellent vapor barrier both inside and out. If the inner skin is replaced with T&G wood or another permeable material then a good vapor barrier should be included for sure. Condensation will occur inside the wall if the water vapor can get into the cavity.

[TeddyK]

I’ve looked at this from my (rear corner) bed numerous times. The right 2 gaps (of 3 inside seam) are 3/16”. Thread is good reminder to seal. Can I use clear silicon should I use same as exterior? Anyone else have a weird seam inside. Looks to be from factory no int/ext damage or accidents, ext seams perfect only time visible is lying on bed head under window. No shell separation (bumper/rub rail leak was professionally repaired by PO) No reason to try to close gaps w addition rivets.

Is this indicative of anything I may not know? How long is the interior seam overlaps anyone know? Thank in advance

[Jcondon]

Originally Posted by TeddyK

I’ve looked at this from my (rear corner) bed numerous times. The right 2 gaps (of 3 inside seam) are 3/16”. Thread is good reminder to seal. Can I use clear silicon should I use same as exterior? Anyone else have a weird seam inside. Looks to be from factory no int/ext damage or accidents, ext seams perfect only time visible is lying on bed head under window. No shell separation (bumper/rub rail leak was professionally repaired by PO) No reason to try to close gaps w addition rivets.

Is this indicative of anything I may not know? How long is the interior seam overlaps anyone know? Thank in advance

The overlap varies widely. No vapor barrier is perfect and it doesn’t need to be. If you caulk this gap with clear silicone be sure it’s a neutral cure silicone. If it smells like pickles don’t use it.

[TeddyK]

Perfect. It’ll take 5 mins twice. I’ll mask w blue tape do 2 step. Deep fill, wait half cure time> 2nd application. Having builtnflipped house and rentals biggest error pp make caulk or silicone is trying to fill big holes in one application. Doesn’t cure properly never stops shrinking eventually leaks.

Correct there’s vapor breaks all over these.

Assume overlap must be 1” minimum thru out rivets consistently on center 1/2” from finished exposed edge.

Good point 👍 pickles smell no bueno. This isn’t a shower or wet area no needs for super duty just routine maintenance aesthetics my own peace of mind

Originally Posted by Jcondon

The overlap varies widely. No vapor barrier is perfect and it doesn’t need to be. If you caulk this gap with clear silicone be sure it’s a neutral cure silicone. If it smells like pickles don’t use it.

[gator.bigfoot]

Take a sealed plastic bag put it in the sun for a while and then into a fridge and vice versa. You will have condensation inside depending on the temperature. This is the dew point. There will always be air getting between the walls. The only way to prevent it is with spray foam. The important thing is that it can get back out. Otherwise you will end up with mold. Rockwool's board insulation is amazing stuff. It can get wet and still work. But like foam insulation it's hard to work with for something like an RV. That's why it's used for on the roof or outside walls. Not for inside. Pink fluffy fiberglass is easy to work with. You can shove it anywhere and it won't break into small pieces. It conforms. Not so with anything that Rockwool has. They have their applications and each has advantages and disadvantages. But one of the biggest advantages of rockwool is that mice don't like it.

[Vernation]

I was just assuming that there would be condensation no matter which insulation you chose. So I thought having something that does not absorb moisture was the way to go.


Does Rockwool break apart? I was sort of wondering about what the effects of bouncing down the road would have on it, if it isn't as flexible/ forgiving as fiberglass.
Would I just end up with tiny pieces of rock at the bottom of the walls after a while?

[Jcondon]

I use Armaflex sheets on my builds. It’s more expensive but extremely effective. Totally impervious to moisture. I use two layers of 3/4”. The first layer fully adhered to the skin. Then I wire and install the second layer cutting around the wiring. Then I use Black spray foam on any voids, and Armaflex tape over the cuts and on the ribs. This is the best that you can do. Armaflex is a green building product used in schools and hospitals as duct liner and mechanical insulation. It’s about 4.5 R value per inch depending on the manufacture.

[Ronyx]

I think this is just like one would do in a home. Vapor barrier like like plastic sheeting over the insulation to prevent moisture from collecting in the insulation from the interior and potentially creating mold. Also helps eliminate drafts. If the inner skin of the trailer is off and your insulating why not just put a plastic vapor barrier over it before putting the skin on?

[Snowey BC]

I’ve got rock wool insulation in my home. Just saying it affects wifi. It’s got copper in it. So expect it to impact cell phone and internet.

[foobar]

Originally Posted by Snowey BC

I’ve got rock wool insulation in my home. Just saying it affects wifi. It’s got copper in it. So expect it to impact cell phone and internet.

If it has copper in it, then it is not a good idea to put it in contact with aluminum.

Aluminum and copper plus moisture = galvanic corrosion, with aluminum representing the sacrificial metal that gets damaged or destroyed.

I don't know if rock wool has copper in it or not. If it does, it is not a good idea to use it in contact with aluminum.

If you are skeptical, just Google search copper plus aluminum ships/sailboats. I have seen aluminum hulled sailboats sink because someone dropped copper coins in the bildge and the aluminum hull was destroyed in the area that was in contact with the coins. The degradation only took a few weeks or months depending on the ambient temperature and then bye bye boat. Of course, this process will take longer in the Airstream because moisture is not continously present.

[gator.bigfoot]

Originally Posted by Vernation

I was just assuming that there would be condensation no matter which insulation you chose. So I thought having something that does not absorb moisture was the way to go.


Does Rockwool break apart? I was sort of wondering about what the effects of bouncing down the road would have on it, if it isn't as flexible/ forgiving as fiberglass.
Would I just end up with tiny pieces of rock at the bottom of the walls after a while?

No it won't break apart. It's not that brittle. But you can't stuff it into small joints like fiberglass. It's a lot more delicate to work with when going around electrical boxes and wires and definitely takes more time. But it's a lot better product. And that's coming from a guy who used to work in R&D for Owens.

[Pimms]

I've heard that mice hate Rockwool.

[andyherman]

FWIW, the regular Rockwool batts are much easier to work with than any pink insulation and you don't have to put on a clown suit to install it. It's really easy to cut (I used a carpet knife), you don't have to worry about getting pricked by shards of fiberglass from the pink stuff or breathing in pieces of the pink insulation that typically break off, and it definitely doesn't sag. Better yet, the R value is higher than the comparable R value for the same thickness of pink insulation and it's pretty easy to slice the batts to get a thinner cross-section that would be needed in the walls of an AS.

Also, unlike the pink stuff, moisture doesn't affect it's insulating properties. However, it does cost more than the pink stuff, but is well worth it in my opinion.

I used both the R-13 and R-23 in my two cabins and couldn't be more pleased with the results. Granted an Airstream isn't a cabin, but I see no areas in my AS where using Rockwool would/should be an issue.

[Vernation]

"If it has copper in it, then it is not a good idea to put it in contact with aluminum."


I have some understanding of the galvanic corrosion thing. (Differing metals + moisture and/or electricity = bad)

I did not read that it had copper in it, but I thought I had read that it has some steel in it, which to me is also worrisome for the same reason. (Though I don't think it has a lot...)



The spec sheet does say this:
Corrosion Resistance
Stress Corrosion Cracking Tendency of Austenitic Stainless Steel - Passed
Corrosion of Steel - Passed


Not sure that's any comfort given that we're dealing with aluminum...

[foobar]

Originally Posted by Vernation

"If it has copper in it, then it is not a good idea to put it in contact with aluminum."


I have some understanding of the galvanic corrosion thing. (Differing metals + moisture and/or electricity = bad)

I did not read that it had copper in it, but I thought I had read that it has some steel in it, which to me is also worrisome for the same reason. (Though I don't think it has a lot...)



The spec sheet does say this:
Corrosion Resistance
Stress Corrosion Cracking Tendency of Austenitic Stainless Steel - Passed
Corrosion of Steel - Passed


Not sure that's any comfort given that we're dealing with aluminum...

Unfortunately, without knowing the exact breakdown of the composition of the rock wool, we won't know about it's behavior in contact with aluminum (and also the inevitable condensation on the aluminum).

From a web source: "ROCKWOOL insulation is a rock-based mineral fiber insulation comprised of Basalt rock and Recycled Slag. Basalt is a volcanic rock (abundant in the earth), and slag is a by-product of the steel and copper industry. The minerals are melted and spun into fibers."

Basically, since it's made from a combination of basalt and the waste products from steel and copper production, there will be little consistency to rock wool composition from one batch to another and rock wool will definitely have various metals in it's composition.

It's a crap shoot whether or not you will have galvanic corrosion issues when using this in contact with aluminum in an Airstream.

Not to rain on your parade here, but if it was my trailer, I would look for a more appropriate, less risky insulation like Armaflex.

[Vernation]

Here's why I think there might be some metal involved. From their FAQ section: (Because if it had no metal, they would say that, instead they say it contains no heavy metal)

11) Does ROCKWOOL slag contain heavy metals?
ROCKWOOL products do not contain any heavy metals. Please contact ROCKWOOL Technical Support to receive specific information on materials found in ROCKWOOL products.


From their Safe Use Instruction Sheet (Altered a bit --the binders are in their own columns but it doesn't show up well here):


Product Family, Stone wool (a, b), Non added formaldehyde or Phenol binder, Syrups& hydrolysed starch, Mineral Oil

I. 97% <3% -<1% <0.2%
II. 97% -<3% <1% <0.2%
III. 94-96% -<6% <1% <0.2%
IV. 94-96% -<6% <1% <0.2%
V. 97% -<3% <1% <0.2%
VI. 97% -<3% <1% <0.2%
a:Man-made vitreous (silicate) fibres with random orientation with alkaline oxide and alkali earth oxide (Na2O+K2O+CaO+ MgO+BaO) content greater than 18 % by weight and fulfilling Note Q
conditions
b:Man Made Vitreous Wool Fibres are IARC classified as Group 3 (not classifiable as to their carcinogenicity to humans)
Possible facing materials:Mineral fleece. Aluminium foil, Aluminium foil reinforced mineral fiber grid, PE craft paper, Wired mesh, PP film, Plaster board, Mineral cloth, Bitumen.


It says aluminum foil is a suitable facing material, which is somewhat heartening, but then of course no one cares if their facing material develops corrosion.