Insulation effectiveness tests

[Zeppelinium]

I was just looking again at this post
http://www.airforums.com/forums/536039-post512.html
and Wabbiter's following post.

Using 1" fiberglass behind foil would allow you to put a small air gap between the foil and the outside shell. So what should a test panel look like?

1. foil against outside panel and full fiberglass (1-1/2") behind it, or
2. foil 1/2" off the outside panel and then full glass (1") behind it.

Despite the technical attractiveness of #2, it would be a difficult installation [in the real Airstream] and might not last, eg, the tape or other sealing method would fail over time.

The advantage of #1 is you don't really need to seal the foil, since a full fiberglass pack behind the foil would effectively stop/slow any air movement. You'd seal it, of course, but a subsequent failure of the tape/glue wouldn't have a great impact.

Zep

[ticki2]

Originally Posted by boatdoc

Hi FC7039;


Even if the Urethane closed cell foam can be successfully applied, aside of all other complications which I have not mentioned, there is a reason why airstreams are riveted and not welded. The reason is that the structure must flex. How many aircraft did you see that are welded? What happens when frame separation goes unnoticed for a while. At each flex point the foam will turn into dust. Frames in Airstream's are not built as stiff platform.
They need to be locked into the shell to form a structural assembly, and YES they do flex.

"Boatdoc"

Interesting point. So what type of insulation do aircraft use.

Closed cell foam is used in the building industry all the time and can be sprayed horizontal ,vertical , and upside down . I would not think application is a problem ( not talking Great Stuff , but real stuff )

[boatdoc]

Originally Posted by ticki2

Interesting point. So what type of insulation do aircraft use.

Closed cell foam is used in the building industry all the time and can be sprayed horizontal ,vertical , and upside down . I would not think application is a problem ( not talking Great Stuff , but real stuff )

Hi ticki2; That is a good question for Doorgunner. I believe that most aircraft uses blanket type foil insulation. Send him a Pm and you will most likely get answer that you cannot afford it.
Addressing the spray or pour foam issue, please read some of my previous posts in reference to expanding foams. It must be closed cell or else it will absorb moisture which negates the "R" value by increased transfer of temps heat or cold, by contact.

Thanks, "Boatdoc"

[Jim & Susan]

Originally Posted by boatdoc

Hi ticki2; That is a good question for Doorgunner. I believe that most aircraft uses blanket type foil insulation. Send him a Pm and you will most likely get answer that you cannot afford it.....

Thanks, "Boatdoc"

That was the answer I got from a friend of mine who is an A&P mechanic. It's good stuff but the cost is very high.

JIm

[AirstreamGypsy]

Originally Posted by Zeppelinium

Using 1" fiberglass behind foil would allow you to put a small air gap between the foil and the outside shell. So what should a test panel look like?

1. foil against outside panel and full fiberglass (1-1/2") behind it, or
2. foil 1/2" off the outside panel and then full glass (1") behind it.

Could you put the fiberglass against the outside and then the foil? That would give the stand off you want?

[ticki2]

Originally Posted by boatdoc

Hi ticki2; That is a good question for Doorgunner. I believe that most aircraft uses blanket type foil insulation. Send him a Pm and you will most likely get answer that you cannot afford it.
Addressing the spray or pour foam issue, please read some of my previous posts in reference to expanding foams. It must be closed cell or else it will absorb moisture which negates the "R" value by increased transfer of temps heat or cold, by contact.

Thanks, "Boatdoc"

I was talking about closed cell foam , it is also used in refer trucks and trailers . I happen to have an old military trailer ( 1958 ) that is built with a sandwiched wall , inner layer of alum , 2" foam insulation , and alum outer layer . While customizing it into a work trailer I had some of the wall section open . None of the foam had pulverized after 50 years. This is a trailer that was ment to be dropped to the ground by a chopper and hauled where no roads exist.

Thanks for the tip on doorgunner.

[boatdoc]

Originally Posted by ticki2

I was talking about closed cell foam , it is also used in refer trucks and trailers . I happen to have an old military trailer ( 1958 ) that is built with a sandwiched wall , inner layer of alum , 2" foam insulation , and alum outer layer . While customizing it into a work trailer I had some of the wall section open . None of the foam had pulverized after 50 years. This is a trailer that was ment to be dropped to the ground by a chopper and hauled where no roads exist.

Thanks for the tip on doorgunner.

Hi ticki2; You are correct. Military used a closed cell foam. The truck structure was made rigid however, this is why it withstood the years of use.
If I am not mistaken it was 4 lbs weight which is hard to destroy to begin with. Some foams did contain linear poly compounds making them more resilient, although I am not sure what the military used back in 1958. If you pay attention to tests results performed by Zep, you will realize that in order to improve on basic insulation is not that simple of a task. It is not cheap or easy to install properly and end result will vary under different conditions.

To be honest [without offending anyone] some of the vintage AS's twist and buckle on bad roads because many of them do not have a sufficiently stiff frame platform, or/and the attaching points of the shell to the frame need attention. How long do you think 2 lbs density foam will survive under those conditions? Urethane foam in dust form can create a very unhealthy condition inside your AS. You will be breathing it in, because it is light enough to get airborne every time you stir the air inside. And yes, I know that there are inner walls. But, the inner walls do not offer a perfect seal in many places.

We can take this insulation issue into the infinity, but the question will still remain, why O why?

You want an air space? Glue in urethane 3/4" foam strips to the outside skin or place glass insulation first with vapor barrier facing inside, then cover it with bubble foil glued in at the edges, and even if you like add another layer of thin glass insulation on top of the foil. It may make you happy because
you just gained a whole 1 point in "R" value. I personally, do not even like the idea of fiberglass batting against inner wall unless it is sealed by paper backing, simply because sooner or later glass will become airborne. There is no doubt in my mind, what those extensive experimental tests which Zep is performing are telling me. Too many variables, too much difficulties not enough results. If anyone chooses to discredit Zep's findings then prove him wrong. In the mean time let's just go camping. Thanks, "Boatdoc"

[Jim & Susan]

Hey Zep, here's an idea for you. Instead of the canned spray foam stuff, have you thought about looking for a commercial insulation company that might spray a test box for you with something similar to the stuff I referenced back in post 29? I suspect that if you approach one of them and explain what you are doing, they may set you up for free. You could maybe go to one of their jobs and fill the "wall" while they are working on a building somewhere. After all, you don't need much foam to fill that small test wall.

Just thinking out loud again.

Jim

[Wabbiteer]

With recent thirty nights below zero still near and dear I confess heat and insulation are the only things I was to talk about!

Want to hear about Ultra-High-Bonding 3M foam tape and the 1/16th aerospace silicone sheeting soon to be delivered that will get installed as thermal barriers over the shell rib to interior liners interface?

Or the stainless steel heat exchanger and insulated tank I'm trying to shoehorn in to use with solar hot water collectors I have stashed to provide non-propane heat when boondocking?

Any how - one spot I see foam-in-a-can being good for is to drill and fill the shell ribs to keep twenty little chimneys from allowing condensation cycles from occurring or the hard-won heat I'd trying to bottle up from touching an uninsulated air space on my side of the shell!

[Zeppelinium]

Originally Posted by Wabbiteer

..Want to hear about Ultra-High-Bonding 3M foam tape and the 1/16th aerospace silicone sheeting soon to be delivered that will get installed as thermal barriers over the shell rib to interior liners interface?
...
Any how - one spot I see foam-in-a-can being good for is to drill and fill the shell ribs to keep twenty little chimneys from allowing condensation cycles from occurring or the hard-won heat I'd trying to bottle up from touching an uninsulated air space on my side of the shell!

I hope you got three dogs!

Yes, want to hear right now!

Agree on using spray-in foam for the little leaks around perforations.

More later...off to build a dome!

Zep

[InsideOut]

I'd be careful with some of the spray foam insulations...if you overdo them or apply them unevenly they might expand and oil can the aluminum skins. I recently had a project that the GC applied the foam insulation too dense inside the walls and it bowed the gypboard once it was finished expanding. The gyp had to be removed, the insulation trimmed and then new gyp used...did not make his day!

Shari

[ticki2]

Originally Posted by InsideOut

I'd be careful with some of the spray foam insulations...if you overdo them or apply them unevenly they might expand and oil can the aluminum skins. I recently had a project that the GC applied the foam insulation too dense inside the walls and it bowed the gypboard once it was finished expanding. The gyp had to be removed, the insulation trimmed and then new gyp used...did not make his day!

Shari

I have seen it jamb windows and doors shut when trying to use it in a cavity . The inner and outer skin on an AS is nowhere near stiff enough to try and spray between them , the inner skin should be removed . I would think the only time foam would be considered is on a full monty.

[Wabbiteer]

Yikes - when I saw I'd mis-posted the edit option was gone...

Foam in a can might be my secret weapon to lock in foil-foam-foil but I won't be 'filling' any cavities.. Sorry & thanks for responding!

[Wabbiteer]

Looking at other posts showing clean and even polished interiors has made me ask if the most perfect polished foil radiant insulation is already there - the inside of exterior shell 2024 aluminum???

Lessoning oxidation and texture with a quick polish and fighting off remaining adhesive left on it before making up the "air gap" certainly would mean a more insulated section.... right?

[Jim & Susan]

Originally Posted by Wabbiteer

Looking at other posts showing clean and even polished interiors has made me ask if the most perfect polished foil radiant insulation is already there - the inside of exterior shell 2024 aluminum???

Lessoning oxidation and texture with a quick polish and fighting off remaining adhesive left on it before making up the "air gap" certainly would mean a more insulated section.... right?

Well, sorta. There is virtually no part of the interior of the walls in mine that is clean and "polished". The interior walls are actually painted on the back. The inside of the exterior skin is covered in the glue substance that originally was used to attach the pink stuff to the shell. In other words, there isn't much there to reflect anything, if that's what you mean.

Jim

[Jim & Susan]

Originally Posted by InsideOut

I'd be careful with some of the spray foam insulations...if you overdo them or apply them unevenly they might expand and oil can the aluminum skins......

Shari

The thread that I mentioned above discussing the spray foam stuff contains a post from a fellow who actually had this type of problem. I believe he blamed it on heat, IIRC. Your scenario was more likely the problem, I'll bet.

The reason that I bring up the spray foam insulation (professional grade, not the canned stuff from HUD) is that this post in the previous thread is the only instance I've read on this forum of anybody actually using the stuff in an Airstream. There may be others, but I havn't found them. That sort of speaks volumes to me. Still it would be nice to see how it stands up against the other methods Zep is testing.

Just my 2 kopecks.

Jim

[Dan Clayton]

Spray foam will also wrap the sides of the trailer, and the front and back panel. It does not seem to harm the curved sides, as there is no place for the metal to warp too. I did alot of reasearch on the subject, but the one thing that was missed is that the really good foam insulation generates heat, and a alot of it. Over 200* You wont notice the panels warping at first, but as they cool it will look like a wave, the metal is just too thin. Spray foam works great on automotive sheet metal, and fiberglass. Plus the stuff is a real mess to clean up, and you will spend countless hours triming it down so you can get the walls back in. There is some foams that dont use as much heat, but they are worth paying the money for. Do yourself a favor, stick with foil and pink insulation, it easy to work with and it works great for keeping heat in when you want it and keeping heat out when you need it. I'm sure nobody want's to have to reskin there intire tralier twice like I did !

[boatdoc]

Originally Posted by Dan Clayton

Spray foam will also wrap the sides of the trailer, and the front and back panel. It does not seem to harm the curved sides, as there is no place for the metal to warp too. I did alot of reasearch on the subject, but the one thing that was missed is that the really good foam insulation generates heat, and a alot of it. Over 200* You wont notice the panels warping at first, but as they cool it will look like a wave, the metal is just too thin. Spray foam works great on automotive sheet metal, and fiberglass. Plus the stuff is a real mess to clean up, and you will spend countless hours triming it down so you can get the walls back in. There is some foams that dont use as much heat, but they are worth paying the money for. Do yourself a favor, stick with foil and pink insulation, it easy to work with and it works great for keeping heat in when you want it and keeping heat out when you need it. I'm sure nobody want's to have to reskin there intire tralier twice like I did !

Thank you Dan Clayton;
I have tried to convince everyone in a gentle way that spray foams will absorb moisture in uncontrolled environment. Pour foams have numerous pitfalls such as, Difficulties In Application, Heat Distortion, Expansion Distortion, Fragmentation Due to Vibrations and flex, and a host of other related problems. As you have said Dan, pour foam generates high heat which will deform inner and outer skins by bulging them out, as it is generating a lot of pressure during the chemical reaction. Heat alone will bulge out outer panels. For those who do not believe it, set your hair dryer on high and heat one panel for 10 minutes. If that does not convince you to abandon the idea, nothing will, and you will ruin your AS. For the individuals who would like to tell me that their AS sits in a 160 degree desert heat and the panels do not distort, I will say this. Gradual heating of AS by the hot sun expands entire trailer evenly. This is why panels do not bulge. The aluminum ribs are of the same temperature then, and expand at the same rate with the skins. Aluminum has a very high expansion rate once it is heated. When you pour foam into one section, only that section is heated by the reaction in the setting foam to about 200 degrees. Surrounding areas are of ambient temperature and cannot expand at the same rate. The expanded material has to go somewhere. The ribs will contain that expansion and the only place the skin can go, is out.

I have worked with many different pour foams for forty years. If you think that you know more, go ahead and see for yourself. Just to encapsulate and insulate my plastic tub into a 3MM plywood walled enclosure, I had to do eight consecutive small layer pours to keep the heat from melting the tub. Have I had poured it in one shot, my tub would have been molted mess. One thing is for certain, there is much more to foams than you think. Low temperature setting foams are too expensive and still have many future negatives connected with application in flexing AS shell. Why are some people insisting on getting in trouble? Sorry for being blunt in getting my point across, but I hate to see another person going through what Mr, Clayton has gone through. I do not wish to waste my time to comment anymore on this issue. I am certain that at least some will appreciate your story Mr, Clayton. Thank you "Boatdoc"

[Zeppelinium]

The data will be in the next three posts, with a summary at the end.

First, the box insulationn was enhanced. Overall the insulation was increased an average of 55% from previous tests.

Second, it was plain that wind velocity had a significant impact on the data, so some of the panels showed wide variations in insulating capability, just from the differing winds on a particular test night.

Third, two test parameters were used--how fast did the water bottle cool down and how warm was the inside panel compared to the inside air. I assumed these would provide the same answer, but they did not. Correlation was fair, so you'll have to decide for yourself which was the better data.

Here's the raw data charts:

Air only. This panel had nothing inside.




Bubble foil from Home Depot. The foil was suspended mid-way between the panels and glued in place so there was no air leakage path. Due to unexpected data, both this panel and the Prodex panel were dissassembled to check that the seals were good inside--they were.




Canned Foam. This was the "doesn't bow window frames" version of Great Stuff. It remained flexible (maybe it won't turn to dust as the Airstream flexes) and did not keep expanding when it came to a panel or foil. I think this has some useful applications in our Airstreams, but in small areas.




Cannned foam with Rib. A 10" by 1" channel was cut into the foam along one edge of the panel and a rib installed with 5 pop rivets on each face. The voids were re-filled with foam. This was the only test with a rib, but shows the significant effect that the conductive metal path has on total insulation capability. I did some back of the envelope calculations and it turns out that this construction had approximately the same rib length per unit area of panel as the Airstream shell has, within a factor of 2.





more...

[Zeppelinium]

Glass Mat. I have two panels, one moderately shiny and the other moderately dull. I only used the dull one in this test.





Prodex. Thanks to Craig (2333), I had a few square feet of Prodex. This panel was perhaps the best made of all of them.




Prodex w/ 1/2" of Glass Mat. The previous panel was opened and 1/2" of glass mat was placed on the inside side of the prodex, eg, the side toward the inside of the box (shell). Due to the way the prodex had been put in the panel in the first place, this resulted in a panel with 3/4" airspace on the outer side, the Prodex, then the remaining 1/2" full of glass mat.




Prodex w/ full Glass Mat. This was the styrene panel (see data in the next post). All the styrene in the center 10" x 10" space was removed and a sheet of 12x12" prodex, with edges folded up along the insides and glued, was placed against the outer panel. The remaining space was filled with glass mat.




more...