Help Interpret this Response from the Rockwool People

[Vernation]

"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."

You're not raining on my parade. I want what's best for the longevity of the trailer, too.

I appreciate the comments and differing points of view. Lots of food for thought.
Thank you!

[foobar]

Did a little digging:

Reference: https://www.engineersedge.com/galvanic_capatability.htm

See attached images.

This isn't my area of expertise. Given that the metals in the rock wool are bound to one or more Oxygen atoms instead of being in pure metal form, I don't know how active they will be in terms of galvanic corrosion potential. The metal oxides might be inert.

Anyway, I do believe there are better insulation materials for this application that would represent zero risk.

I think you will need to click on these images in order to see a decently sized, readable image.

[on-a-roll]

I used rockwool in my 74 Argosy trailer during its shell off rebuild. That was 8 years ago. I have traveled 43,000 mile pulling this trailer. Good roads. Bad roads. No roads. Full time for 18 months. All kinds of weather conditions. Snow. Hail. Wind. Sun.


At one point I had a leaky window which required removing a bit of inside shell to get ti the problem. The rockwool looked as good as the day I put it. There was zero corrosion seen. Everything looked as good as the day it went in.I used 3M spray glue to hold it in place.

[Vernation]

@on-a-roll
Which Rockwool Product did you use?

[DrivingDan]

A vapor barrier means on one side only. Moisture will penetrate to an inner wall no matter what (unless its a vacuum chamber), and it needs a means of escape for equalization. If there were barriers on all sides or in the batting that would be a problem. With a house the barrier is on the outside and the inside breathes.

With no barrier (the AL skin isn’t one) the best option is to have a relatively breathable insulation, I think this is what they are recommending.

[Jcondon]

Originally Posted by DrivingDan

A vapor barrier means on one side only. Moisture will penetrate to an inner wall no matter what (unless its a vacuum chamber), and it needs a means of escape for equalization. If there were barriers on all sides or in the batting that would be a problem. With a house the barrier is on the outside and the inside breathes.

With no barrier (the AL skin isn’t one) the best option is to have a relatively breathable insulation, I think this is what they are recommending.

Negative on that Driving Dan. In California you may get by with a vapor barrier on the exterior but in heating climates the vapor barrier is always on the inside. Otherwise the air going through the insulation would reach the dew point somewhere within the wall insulation. This results in soggy insulation every time. The aluminum skin is a near perfect vapor barrier on the inside except the joints. All in all it's almost perfect. I warmer climates where the outside is humid and the inside is air conditioned the vapor barrier would be better on the outside. Since trailers have wheels, a vapor barrier on both sides is perfect.

[Gene]

The world of insulation has changed in the last generation and although I read about it, a lot is kind of hard for me to completely understand. But...you only put a vapor barrier on one side because water vapor will penetrate just about anything. Every product has a permabili=ty rating and none are zero. With a barrier on each side, the moisture will get into the wall cavity, but not out (I guess there is more air pressure outside pushing some vapor into the cavity than on the inside pushing out).

Fiberglass is usually installed badly—you need a complete air seal (different than vapor barrierand permeability ratings) around the fiberglass to prevent cold or hot air from getting past the edges. Spray foam will seal against air intrusion much better, though it can be messy to work with. Unless you have a shell off, that could be a stopper. There are different spray foams, but you need to research the mess factor.

I know rock wool can be a very good home insulation, but in a trailer I have no idea. Neither did the manufacturer so they disclaimed responsibility as their lawyer would tell them to do—it is simple, they haven't tested it, so they are not going to recommend it.

I expect the fiberglass as installed in Airstreams is often damp because the aluminum walls are a pretty good barrier. If the fiberglass has a paper side (it would be facing to the interior) that is the vapor barrier. Most installers have not in the past taped the edges down and sealed around electrical receptacles, so the fiberglass' efficiency is reduced by around 50%. If fiberglass does not have a vapor barrier, and it gets wet (remember, Airstreams are leakers), it will slide down into clumps and you have little or no insulation.

Houses are now built with multiple layers of insulation including foam board on the outside and a variety of products, often not fiberglass batts, on the interior. A rain screen will be between the outside layers of foam board so water doesn't accumulate behind the siding and rot either side. Some of the pictures of insulation systems on newer houses are quite complicated and some may have the vapor barrier on the inside, but it is usually to the interior side of the rain screen. A rain screen is not like a screen door—it is a thin air space created to let the outside of foam board or other sheathing and the interior of the siding dry out.

For historians, many years ago, maybe the 1970's, Airstream tried spray foam and it worked very badly. It crumbled eventually and crusted a mess inside the walls and did not insulate. They went back to fiberglass. Foam is many times better than it was then, but Airstream has a principle—if it failed since, never try it again. I think they tried thermal pane windows around then and they leaked, so no more. It would cost more too. Airstream is a very hidebound company that is suspicious of new things and anything that increases costs by even pennies. The result is that the furnace or A/C in Airstreams run a lot more, you use a lot more propane, and it is hard to heatt or cool them. Just about anything will improve Airstream insulation except the fiberglass batts they still use.

[Jcondon]

Originally Posted by Gene

The world of insulation has changed in the last generation and although I read about it, a lot is kind of hard for me to completely understand. But...you only put a vapor barrier on one side because water vapor will penetrate just about anything. Every product has a permabili=ty rating and none are zero. With a barrier on each side, the moisture will get into the wall cavity, but not out (I guess there is more air pressure outside pushing some vapor into the cavity than on the inside pushing out).

Fiberglass is usually installed badly—you need a complete air seal (different than vapor barrierand permeability ratings) around the fiberglass to prevent cold or hot air from getting past the edges. Spray foam will seal against air intrusion much better, though it can be messy to work with. Unless you have a shell off, that could be a stopper. There are different spray foams, but you need to research the mess factor.

I know rock wool can be a very good home insulation, but in a trailer I have no idea. Neither did the manufacturer so they disclaimed responsibility as their lawyer would tell them to do—it is simple, they haven't tested it, so they are not going to recommend it.

I expect the fiberglass as installed in Airstreams is often damp because the aluminum walls are a pretty good barrier. If the fiberglass has a paper side (it would be facing to the interior) that is the vapor barrier. Most installers have not in the past taped the edges down and sealed around electrical receptacles, so the fiberglass' efficiency is reduced by around 50%. If fiberglass does not have a vapor barrier, and it gets wet (remember, Airstreams are leakers), it will slide down into clumps and you have little or no insulation.

Houses are now built with multiple layers of insulation including foam board on the outside and a variety of products, often not fiberglass batts, on the interior. A rain screen will be between the outside layers of foam board so water doesn't accumulate behind the siding and rot either side. Some of the pictures of insulation systems on newer houses are quite complicated and some may have the vapor barrier on the inside, but it is usually to the interior side of the rain screen. A rain screen is not like a screen door—it is a thin air space created to let the outside of foam board or other sheathing and the interior of the siding dry out.

For historians, many years ago, maybe the 1970's, Airstream tried spray foam and it worked very badly. It crumbled eventually and crusted a mess inside the walls and did not insulate. They went back to fiberglass. Foam is many times better than it was then, but Airstream has a principle—if it failed since, never try it again. I think they tried thermal pane windows around then and they leaked, so no more. It would cost more too. Airstream is a very hidebound company that is suspicious of new things and anything that increases costs by even pennies. The result is that the furnace or A/C in Airstreams run a lot more, you use a lot more propane, and it is hard to heatt or cool them. Just about anything will improve Airstream insulation except the fiberglass batts they still use.

The .032 aluminum skin has a vapor permability of zero. The assembly may not but the material certainly does. No matter what insulation is chosen the thermal bridging of the outer skin to ribs and cross members to inner skin greatly derates any higher R value you may attain. The conduction through the shell radiates heat either in or out. The window and door frames do also. Chasing the highest R value possible should be accompanied by cutting the thermal bridging where you can and possibly using ribs and cross members made with materials that are less conductive. And you are right about Airstream being suspicious of new things. Air Forums also. The spray foam was an Ohio thing. I have a 1969 Ohio that had it spray about 2" thick on the subfloor. It was in fine condition and it actually greatly preserved the subfloor. I believe this was because it served as a great vapor barrier on the floor I have not seen it in the walls ever. Not that they didn't try it though.

[Jcondon]

Originally Posted by Jcondon

The .032 aluminum skin has a vapor permability of zero. The assembly may not but the material certainly does. No matter what insulation is chosen the thermal bridging of the outer skin to ribs and cross members to inner skin greatly derates any higher R value you may attain. The conduction through the shell radiates heat either in or out. The window and door frames do also. Chasing the highest R value possible should be accompanied by cutting the thermal bridging where you can and possibly using ribs and cross members made with materials that are less conductive. And you are right about Airstream being suspicious of new things. Air Forums also. The spray foam was an Ohio thing. I have a 1969 Ohio that had it spray about 2" thick on the subfloor. It was in fine condition and it actually greatly preserved the subfloor. I believe this was because it served as a great vapor barrier on the floor I have not seen it in the walls ever. Not that they didn't try it though.

The best solution that I have found and that I use in my builds is Armaflex sheets. 2 layers of 3/4". The first is glued tight to the outer skin and sealed to the ribs with black spray foam. Then the wiring goes in and a second layer of 3/4" glued to the first and airsealed to the ribs and crossmembers again with foam and caulk. The gaps for the wiring is also spray foamed and covered with 1.8" Armaflex tape. Then the ribs and crossmembers are taped as a thermal break and the inner skin is attached through the thermal bridge tape. Foam gaskets are used on the electrical devices to totally air seal the interior. I think this is the best you can do with the 1.5" space.

[Jcondon]

Originally Posted by Gene

The world of insulation has changed in the last generation and although I read about it, a lot is kind of hard for me to completely understand. But...you only put a vapor barrier on one side because water vapor will penetrate just about anything. Every product has a permabili=ty rating and none are zero. With a barrier on each side, the moisture will get into the wall cavity, but not out (I guess there is more air pressure outside pushing some vapor into the cavity than on the inside pushing out).

Fiberglass is usually installed badly—you need a complete air seal (different than vapor barrierand permeability ratings) around the fiberglass to prevent cold or hot air from getting past the edges. Spray foam will seal against air intrusion much better, though it can be messy to work with. Unless you have a shell off, that could be a stopper. There are different spray foams, but you need to research the mess factor.

I know rock wool can be a very good home insulation, but in a trailer I have no idea. Neither did the manufacturer so they disclaimed responsibility as their lawyer would tell them to do—it is simple, they haven't tested it, so they are not going to recommend it.

I expect the fiberglass as installed in Airstreams is often damp because the aluminum walls are a pretty good barrier. If the fiberglass has a paper side (it would be facing to the interior) that is the vapor barrier. Most installers have not in the past taped the edges down and sealed around electrical receptacles, so the fiberglass' efficiency is reduced by around 50%. If fiberglass does not have a vapor barrier, and it gets wet (remember, Airstreams are leakers), it will slide down into clumps and you have little or no insulation.

Houses are now built with multiple layers of insulation including foam board on the outside and a variety of products, often not fiberglass batts, on the interior. A rain screen will be between the outside layers of foam board so water doesn't accumulate behind the siding and rot either side. Some of the pictures of insulation systems on newer houses are quite complicated and some may have the vapor barrier on the inside, but it is usually to the interior side of the rain screen. A rain screen is not like a screen door—it is a thin air space created to let the outside of foam board or other sheathing and the interior of the siding dry out.

For historians, many years ago, maybe the 1970's, Airstream tried spray foam and it worked very badly. It crumbled eventually and crusted a mess inside the walls and did not insulate. They went back to fiberglass. Foam is many times better than it was then, but Airstream has a principle—if it failed since, never try it again. I think they tried thermal pane windows around then and they leaked, so no more. It would cost more too. Airstream is a very hidebound company that is suspicious of new things and anything that increases costs by even pennies. The result is that the furnace or A/C in Airstreams run a lot more, you use a lot more propane, and it is hard to heatt or cool them. Just about anything will improve Airstream insulation except the fiberglass batts they still use.

Interesting fact on the spray foam. In 1969 refrigerant was used as the blowing agent for spray foam. The refrigerant is trapped inside each foam bubble so as you demolish it you are releasing R12 into the atmosphere. I have a sophisticated leak detector that I used when I demolished my floor foam and it was going crazy! I have a video of this but this site is still in 1969 so no way to post. In this same era cans of Dust off keyboard cleaner also contained R12. Up until the early 80's. Now R 12 is $200 a pound or more!

[Vernation]

"Armaflex sheets. 2 layers of 3/4" "


This may seem like a strange comment coming from someone who's contemplating using rocks as their insulation, but


Two layers of Armaflex seems like it would be pretty heavy.


Do you have the weight comparison to fiberglass or Rockwool?

[Jcondon]

Originally Posted by Vernation

"Armaflex sheets. 2 layers of 3/4" "


This may seem like a strange comment coming from someone who's contemplating using rocks as their insulation, but


Two layers of Armaflex seems like it would be pretty heavy.


Do you have the weight comparison to fiberglass or Rockwool?

It’s definitely heavier than fiber glass and about the same as Rockwool board but it is nonporous, will not absorb water, will not support mold, 25/50 fire rated and it has superior acoustical properties. Zero off gassing and it’s a natural vapor barrier. It is fairly expensive but in the whole scheme I feel it’s the best choice. I would use nothing else. https://www.zoro.com/static/cms/enha...nsxxa5fc98.pdf

[on-a-roll]

I used unfaced Lowe's Rockwool batts.

I had removed the inner shell. First, I caulked the seams and rivets of the outer shell from the inside to help prevent infiltration. I cut the batts to the appropriate size after separating the batts to 1/2 the thickness. I sprayed 3M glue to inside of the outer shell and applied the batts to the shell.

Wear a good mask and long sleeves and gloves to help stop the glue and possible rockwool fibers being inhaled or causing an irritation problem.

I had opened the inner shell at one point to find a water leak. I'd say after years of partial and full-time use of the camper. The batting looked the same as the day I installed it. Still stuck and still intact.

I have NO disappointments using Rockwool. Many benefits over fiberglass.

[richard5933]

Originally Posted by Jcondon

It’s definitely heavier than fiber glass and about the same as Rockwool board but it is nonporous, will not absorb water, will not support mold, 25/50 fire rated and it has superior acoustical properties. Zero off gassing and it’s a natural vapor barrier. It is fairly expensive but in the whole scheme I feel it’s the best choice. I would use nothing else. https://www.zoro.com/static/cms/enha...nsxxa5fc98.pdf

What would it cost to do an entire trailer like this? How much weight would it add beyond other options?

Looking at the spec sheet for the 3/4" stuff...Two layers of this it would weigh about 4.6 lbs/sq ft and would cost about $6.60/sq ft on Zoro.

Not sure how this compares head-to-head against other insulation options, but on first glance it appears heavier and more expensive, possibly enough so that it's not a viable option for many projects. A quick back of the envelop calculation shows this stuff could add a lot of weight - many hundreds of pounds.

[Jcondon]

Originally Posted by richard5933

What would it cost to do an entire trailer like this? How much weight would it add beyond other options?

Looking at the spec sheet for the 3/4" stuff...Two layers of this it would weigh about 4.6 lbs/sq ft and would cost about $6.60/sq ft on Zoro.

Not sure how this compares head-to-head against other insulation options, but on first glance it appears heavier and more expensive, possibly enough so that it's not a viable option for many projects. A quick back of the envelop calculation shows this stuff could add a lot of weight - many hundreds of pounds.

It is for sure heavier but the added weight can be traded off by using Coosa as the subfloor and making your cabinetry out of aluminum! Also avoiding heavy countertops and tile baths. The superior aucustical properties can be attributed to its density. There is no other choice if you want zero off gassing, non porous, water proof, air barrier, smoke and fire rated, and a excellent R value in a easy to install package. It’s the only insulation I will install.
Weight is always a trade off.

[Jcondon]

Originally Posted by richard5933

What would it cost to do an entire trailer like this? How much weight would it add beyond other options?

Looking at the spec sheet for the 3/4" stuff...Two layers of this it would weigh about 4.6 lbs/sq ft and would cost about $6.60/sq ft on Zoro.

Not sure how this compares head-to-head against other insulation options, but on first glance it appears heavier and more expensive, possibly enough so that it's not a viable option for many projects. A quick back of the envelop calculation shows this stuff could add a lot of weight - many hundreds of pounds.

I’m not sure where you got your weight data but a 200 square foot roll of 3/4” weighs less than 100 pounds. I can easily carry it myself. It is a bit bulky though since it s mostly a gas.

[richard5933]

Originally Posted by Jcondon

I’m not sure where you got your weight data but a 200 square foot roll of 3/4” weighs less than 100 pounds. I can easily carry it myself. It is a bit bulky though since it s mostly a gas.

My initial numbers were taken from a couple of sites listing this in individual 3'x4' sheets. I was actually re-doing the research on the weight while you were posting your replies.

Apparently the weight listed was per carton while the product description showed per sheet. The actual weight for this appears to be just under 1 lb/sq foot when both layers are included. Not as much, but still this can amount to a few hundred pounds or more of additional weight which on some builds might mean substantial compromise elsewhere.

I looks like good stuff, but I'm not sure it is always the best option. To me it all depends on the individual project and goals.

[Jcondon]

Originally Posted by richard5933

My initial numbers were taken from a couple of sites listing this in individual 3'x4' sheets. I was actually re-doing the research on the weight while you were posting your replies.

Apparently the weight listed was per carton while the product description showed per sheet. The actual weight for this appears to be just under 1 lb/sq foot when both layers are included. Not as much, but still this can amount to a few hundred pounds or more of additional weight which on some builds might mean substantial compromise elsewhere.

I looks like good stuff, but I'm not sure it is always the best option. To me it all depends on the individual project and goals.

I have used them all and it’s my opinion that it is the best choice. It’s only downfall is the expense. It’s the first choice for schools and hospitals because it is fiber free and cleanable. Plus zero off gassing. But it does cost more to do it like this.

[Jcondon]

Originally Posted by richard5933

My initial numbers were taken from a couple of sites listing this in individual 3'x4' sheets. I was actually re-doing the research on the weight while you were posting your replies.

Apparently the weight listed was per carton while the product description showed per sheet. The actual weight for this appears to be just under 1 lb/sq foot when both layers are included. Not as much, but still this can amount to a few hundred pounds or more of additional weight which on some builds might mean substantial compromise elsewhere.

I looks like good stuff, but I'm not sure it is always the best option. To me it all depends on the individual project and goals.

Originally Posted by Jcondon

I have used them all and it’s my opinion that it is the best choice. It’s only downfall is the expense. It’s the first choice for schools and hospitals because it is fiber free and cleanable. Plus zero off gassing. But it does cost more to do it like this.

I generally buy wrecks I make a new frame from all new material. Take it in to get it hot dipped galvanized. Then I install new Dexter galvanized axles. Then hot water radiant heat panels. Then a Coosa subfloor with epoxy too coat, then from fiberglass/aluminum composite ribs, all new channel and bows, and new outer skin for the straight sections. Then water cooled HVAC and a stainless steel wet bath. Commercial quality electrical components are next. So the slight added cost for an insulation that meets and exceeds all of the requirements of a quality build is insignificant.

[Dingo Girl]

Originally Posted by Jcondon

It is for sure heavier but the added weight can be traded off by using Coosa as the subfloor and making your cabinetry out of aluminum! Also avoiding heavy countertops and tile baths. The superior aucustical properties can be attributed to its density. There is no other choice if you want zero off gassing, non porous, water proof, air barrier, smoke and fire rated, and a excellent R value in a easy to install package. It’s the only insulation I will install.

Weight is always a trade off.

I absolutely love your cabinetry!