Insulation effectiveness tests

[Zeppelinium]

Originally Posted by FrenchBern

...I don't remember any differences in heat transfer formula or K factors in transfer for convection or contact or radiation. Is this something new? Forgive me but I am getting old.

No, no changes. It's just that thermal properties of materials, when reduced to a simple R-value, assume a standard method of installation. For example, the foil insulations recommend an air space on both sides, becuase they are better at reflection than conduction. On the other hand, glass mat requires a snug installation between drywall and exterior siding in order to prevent convection (when installed vertically--in the attic and horizontal, convection isn't an issue). I think we Airstreamers tend to use materials in a non-standard way sometimes, so thinking about the issues that raises may help us get better insulation performance.

Not to get too technical, but black body radiation is a Kelvin function. We live in a world around 520 degrees above absolute zero, so when the temperature changes 50 degrees, it's really not that much one way or the other when you compute black body radiation. That being said, you know you can feel the radiated heat coming off a hot Airstream shell in the summer. So intuitively I'm thinking that the foil may do better when the sun is burning down on the shell.

Zep

[rangebowdrie]

Frenchbern, in your application, for a walk-in cooler, foam will not give an order of magnitude better performance than fiberglass. The performance of fiberglass batting, when measured under controled laboratory conditions, is not all that bad, hence, the manufactures high rating numbers. The problem, is that under actual real world conditions,it is impossible to achieve these ratings. The primary culprits are air leaks, which carry moisture, and the internal condensation in an AS, which adds more moisture. This moisture wicks thru-out the fiberglass strands,drastically reducing its insulative ability. Also it is almost impossible to install batting perfectly,ie.,no compression, no voids,perfect fits,etc.,and we still have the problem of the air inside the structure,into which we place the batting. In contrast, poured/sprayed foam, is a Freon/inert gas expanded product,in which no air is present. When poured/sprayed, it not only seals the structure from any air leaks, it also displaces the air in the structure. Also, the foam is of a closed-cell nature, which inhibits/slows down the molecular motion that carrys heat. Because of this, and a number of other more esoteric considerations,foam will live-up to it's ratings in actual field useage. Hope some of this helps you. As a footnote, a well polished AS will reflect more of the sun's heat, and stay cooler inside, then a dull finished one.

[boatdoc]

Originally Posted by Zeppelinium

I, myself, am a longevity record. I didn't think I'd see the millenium. Not age, mind you, just risky business. BTW I have 16 of these ancient "laptops" that run on 12V, 1 Amp. If you're a DOS nut and need a data logging machine, let's talk.

Yes, the materials will potentially act differently in the heat. This is only intuitive, but when the outer skin is heated by the sun and is easily 160+ degrees in the desert, radiation might predominate. In cold weather I "feel" like convection and conduction predominate. The foil insulation should have interesting properties in a radiation environment.

Your interpretation of "slightly better" is influenced by the small difference in the numbers in the data. But don't forget that the other five walls are very nearly swamping the panels' performance. That's why I'm going to do tests with a stabilized water bottle position and an internal air temperature sensor. I think those two changes will show quite a bit of difference between the different insulations. Stand by for data.

For those interested, I like the idea of an expanded foam test and will do one this week (do you all agree that using the "low expansion" canned foam at HD will suffice?). I've got two more sets of panels (thank you again, Aerowood), plus I found that I can disassemble a panel without significant damage. I mention this because when I get to the warm tests, I also want to coat the outside and inside of the outer panel with white paint to see what increasing the reflectivity and reducing the emissivity of the outer panel does to its heat transmission--this is more important in a warm weather test than in cold.

WARNING: youse guys are focusing on the insulation performance and forgetting that I'm not simulating the ribs. I'm no expert, but I would bet that the ribs transmit 30-50% of the heat through the shell, if the cavities are well insulated (less of the total if the cavities are poorly insulated). So, putting some foam tape, felt, or cork along the inside flange of the ribs before your reinstall your interior skins would be a significant contribution, even if a thin strip of this stuff only provided a small R-value. Small is bigger than zero, or so I've been told. I believe UWE or someone did this and noted it in a thread.

Zep

Hi Zep; Your theory on the heat loss through the ribs is close to 100% on the money. I did not carry out any sophisticated tests, however I like to tell you what I have observed this past winter with my Argosy sitting in the yard.

Bear in mind that my trailer was insulated with bubble foil. Each panel between the ribs was outlined with 1/2" X2" foam strips attached to the outer skins with 3M 5200. Each panel had a additional supporting strip in the middle of the panel. Bubble foil was cut oversize so that the foil could be wrapped to wards inside wall, along the cross section of each rib. Excess foil was then trimmed about 3/16" above the face of the rib. Slight compression of the bubble foil was purposely done so that the cut high ends of the foil could be compressed as the inner wall skins were installed.

Walking out into the yard one day around lunchtime after 2" snowfall on the previous day, I have noticed a very strange occurrence. Unfortunately my wife was away with my camera and I was unable to take any pictures. Top section of my roof was covered with 2" of snow, but at each rib at about
1 1/4" width, over each rib there was no trace of snow. It looked as someone has cut straight wall passes in the snow. The passes did not have sloped sides, they were very vertical as they were cut clean. Returning an hour later they were slightly wider. With bright sun shining all day the snow did not melt more than 1/2" further from the rib lines by the nightfall . The next day, higher temps melted it all away. When my wife is done with curtains I will perform some temp differentials tests between inside and outside and record the findings. Thanks, "Boatdoc"

[Zeppelinium]

Originally Posted by rangebowdrie

... As a footnote, a well polished AS will reflect more of the sun's heat, and stay cooler inside, then a dull finished one.

See this post about polished aluminum:
http://www.airforums.com/forums/452880-post35.html

I observed in this earlier (and inconclusive) insulation test that "...in two minutes [in the sun], that the mill finish is 20 degrees hotter than the polished finish. The sun angle was pretty low and it was a moderate day here today, so I think it will be even hotter on a hot day in July."

Zep

[Smokin Camel]

In the 70's when in the army I & a couple of freinds were customizing our vans. Granted vans and trailers is an apple to orange comparisons, but a couple of interesting developments happended.

I used fiberglass insulation, one friend used the early spray foam and a third (disaster) tried glueing thin/flexible styrofoam board onto the body.

The immediate things that were noticed was the glued van squeaked like stadium full of mice when it was on the road. The foam pieces also broke loose due to body movement and expansion (we think??). It had a bad sweating problem until the foam loosened up.

The sprayed in foam had better success but eventually had pieces break loose behind the panels. It did have some squeaking but not on near the level of the first van.

Both foam vans had minor sweating problems. It was also a very humid summer in North Carolina.

My fiberglass insulation had no sweating and roade quiet. The glass was put on wtih spray glue to hold it until the panels were in.

Now we don't (at least I hope not!) ride in our trailers so sqeaking is probably not an issue. Sweating had more to do with the technique of applications. I do wonder if spray foam will fracture and get loose. It may not matter if it does as it is still held in place and contained in the walls.

Just some food for thought. We ended up pulling the panels from two of the vans and went to fiberglass in all of them.

My van was called the camel (33 gallon gas tank). One time when starting it, a big puff of smoke came out of the tail pipe and one of my soldiers commented "Smokin Camel" The name stuck. The Van was on it's 4th owner last time I saw it which was two years ago...not bad for a 79 Chevy 3/4 ton. As it was such a long lasting vehicle I named my AS after it.

[malconium]

Zep,

It seems to me that you need some way to test the insulation combinations for both conductive and radiat heat loss. Also you might want to factor in something for the direction of the heat loss (through floor, walls and roof). One of the reasons that I feel foil insulation is such a good choice is that a very large percentage of heat loss through the walls and roof of any structure are supposedly radiant heat loss. If I recall the numbers correctly something like 90+ percent of the heat loss up is radiant. Of course when you talk about heat gain duing the summer a major component will also be radiant as long as the AS is not in the shade. Perhaps you could use something like a heat lamp inside your box to simulate a radiant source a bit better.

As a side note this whole issue of insulation types is also related to the type of heat that we chose to use in our Airstreams. I want to use direct radiant heating in large part because it gets the heat energy directly to the occupants (by radiant transfer) without relying on first heating the air inside the trailer and then the occupants (by conductive transfer). Of course when matched with foil insulation that blocks radiant heat loss this seams like a very nicely matched combination.

Malcolm

[rangebowdrie]

It's to bad that foam has had such a bad reputation, due in large part because of the prevelance and general useage of the cheap squirt-can stuff they sell at various stores for home use. The industrial two-part product is so much better that there is little to compare between them. Not like apples/oranges, but more like strawberrys/limes. The squirt stuff "kicks-off" due to reaction with air, the real stuff "kicks-off" due to internal chemical reaction. In all cases, surfaces to be applied to, need to be clean and dirt/grease/oil free.

[Jim & Susan]

Range, we had a pretty lively discussion of the two part foam stuff you're talking about around a year ago. I'll see if I can find that thread and post a link to it here. I was ready to use it, but changed my mind after we talked it out in that thread.

Jim

[Jim & Susan]

Thar she blows! http://www.airforums.com/forums/f4/s...ion-28491.html

[rangebowdrie]

Jim @ Susan, I read the thread that you referenced in your above post. It is a great thread that I was unaware of. My feeling is, with the scores of various formulations of foams for many different applications, the biggest challenge is finding the right one, and the application personnel to apply. There are probebly foams out there used in military applications that are only sold in tank-car lots, such a product would obviously be out of our reach. But, some formulations may be just what the doctor ordered, as far as use in an AS. It may take some effort in tracking down the most ideal product that is available to us, in small amounts, suitable for us. I am going to keep my own recearch going in this direction, I want to foam my own AS, but know that there are indeed different strokes for different folks, and that no one answer will fit all situations.

[boatdoc]

Originally Posted by FC7039

I want to use the spray expanding polyurethane foam. Mainly due to the sealing properties. If I say please will you do a test panel of this. Please. I will be glad to chip in for the cost.

Hi FC7039;
As some others may agree with me the pour or spray foam comes in few different chemical structures. This will require you to be aware of many negatives associated with either the application process, and, or it's effectiveness associated with the lapsed time changes in integrity.

The Great Stuff is NOT a true closed cell foam. If installed in area of existing leaks, it will eventually absorb water. With time your aluminum will suffer greatly from corrosion. As a rule, you should seal the leaks at entry point, not at the exit where the water comes in.

The true closed cell Urethane foam is very costly in spray foam. Pour type closed cell urethane will expand your walls. Despite the relief holes you may provide for expansion it will seriously deform your walls. Second, there is no way to fill the roof section unless it is applied from the nozzle. In the end you will be shocked where this stuff will surface.

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.

In my humble opinion I cannot see the reason why anyone would endure so much difficulty and increased cost of insulating, in order to gain a couple of points in R value where the heat loss or transfer through your windows may overcome those gains in R value anyway. I wonder if you could not gain more by installing UV reflective shield film on your windows, than insulating the shell with urethane foam. In addition to that the heat transfer through contact of the rib with inner walls will transfer perhaps only a negligible amount, but that counts as well. The question is, will the increased cost and difficulties associated with such application overcome the cost of couple pounds of LPG per week of camping?

It is nice to be able to tune-up through extensive scientific tests if we have time, money and equipment to do so. Why not just insulate with basic method, and let's go camping. And while I truly respect and admire Zeppelenium's knowledge in that field, not all of us can take the insulating of the trailer to that measure. Even if I was able do do so, how much is there for me in return? I do not intend to ever camp in a 120 degree desert heat because I could not stand to walk out into it anyway. For those who do, there just may be a valid reason. Please remember, I do not intend to disagree with the scientific measures of gain, it is ONLY my sensible opinion. Thanks, "Boatdoc"

[boatdoc]

Originally Posted by rangebowdrie

Jim @ Susan, I read the thread that you referenced in your above post. It is a great thread that I was unaware of. My feeling is, with the scores of various formulations of foams for many different applications, the biggest challenge is finding the right one, and the application personnel to apply. There are probebly foams out there used in military applications that are only sold in tank-car lots, such a product would obviously be out of our reach. But, some formulations may be just what the doctor ordered, as far as use in an AS. It may take some effort in tracking down the most ideal product that is available to us, in small amounts, suitable for us. I am going to keep my own recearch going in this direction, I want to foam my own AS, but know that there are indeed different strokes for different folks, and that no one answer will fit all situations.

Hi rangebowdrie;
Yes, it would blow your mind of how many different products there are in the foam specialty market. In my ha'y days, I used to drive a Tunnel Hull race boat for Sunoco Fuels [the only Sunoco sponsored boat] APBA 841. Prior to introduction of Safety Capsules, high speed related accidents used to end up in serious injury or death, as the very light and fragile hulls came apart. Sunoco, being concerned about my safety have sent a prominent US aircraft development company to make my boat so called "bullet proof". Two men came in large sophisticated trailer conversion and went to work with 1/2 lbs weight per cubic foot of installed foam. Each tunnel hull was blocked off with special heat shrunk film and 1" hole was drilled at each tunnel hull bow. Boat was hung with bow up at 45 degree and foam was poured in. Excess foam discharge hose was affixed to the pour holes so that the expanding foam would not come in contact with outside gel coat. Apparently there was no solution to clean that excess. Cockpit was then bagged for vacuum forming. Three hours later one man has emerged from a trailer with a 20 lbs mull and piece of plastic in hand. One man held the piece of plastic against the foam filled hull, the other swung the mull as hard as he could while my heart was at my throat. The mull bounced back spinning the man around. Please feel secure now, he said. They had me sign agreement not to allow anyone to have a piece of it, so that it cannot be tested for chemical properties.
All expanded excess foam was collected by them and loaded into their trailer. Not a scrap was left to be found. When I quit racing some years later the boat was purchased back by the company who poured the foam for destruction. There is your sign in today's technology. Thanks, "Boatdoc"

[FrenchBern]

Very interesting boatdoc. Thanks for sharing.

[Zeppelinium]

Originally Posted by boatdoc

...And while I truly respect and admire Zeppelenium's knowledge in that field, not all of us can take the insulating of the trailer to that measure. ...

Thanks, Boatdoc, but the reason I'm testing is that I agree with you. The ribs and windows kill 95% of any improvement you can make in R-value in the cavities. Maybe foil is better for air leaks and mold, but I don't think it does any more than glass mat in the cold. I'm really more interested in how it does when the outside skin is hot hot hot.

...I do not intend to ever camp in a 120 degree desert heat because I could not stand to walk out into it anyway. For those who do, there just may be a valid reason. ...

Acutally, it's a dry heat. But seriously, you are right. The problem in the SW in the summer is that the ambient temperature may be tolerable (95 degrees and 10% humidity is actually OK if you're in the shade), but the sun beating down on the shell can raise the shell temperature to more than 160 degrees. By late afternoon, the insides are at 120. This is not nice. I'm looking for any technique that will reduce this.

The best technique I've found is $150 for a carport tent frame (at the Tools for Less outlet on Tropicana in Vegas) and blue plastic cover! So if you're going to stay more than two days it makes sense to put it up. Better than taking your shell apart to reinsulate.

I think the best move you can make is if you take down some part of the inner shell for other work, eg, taking out windows, put the foil in next to the skin, then the glass mat back in. The combination might be worth it if you've already got your inner skin off.

Zep

[FC7039]

Originally Posted by boatdoc

Hi FC7039;
As some others may agree with me the pour or spray foam comes in few different chemical structures. This will require you to be aware of many negatives associated with either the application process, and, or it's effectiveness associated with the lapsed time changes in integrity.

The Great Stuff is NOT a true closed cell foam. If installed in area of existing leaks, it will eventually absorb water. With time your aluminum will suffer greatly from corrosion. As a rule, you should seal the leaks at entry point, not at the exit where the water comes in.

The true closed cell Urethane foam is very costly in spray foam. Pour type closed cell urethane will expand your walls. Despite the relief holes you may provide for expansion it will seriously deform your walls. Second, there is no way to fill the roof section unless it is applied from the nozzle. In the end you will be shocked where this stuff will surface.

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.

In my humble opinion I cannot see the reason why anyone would endure so much difficulty and increased cost of insulating, in order to gain a couple of points in R value where the heat loss or transfer through your windows may overcome those gains in R value anyway. I wonder if you could not gain more by installing UV reflective shield film on your windows, than insulating the shell with urethane foam. In addition to that the heat transfer through contact of the rib with inner walls will transfer perhaps only a negligible amount, but that counts as well. The question is, will the increased cost and difficulties associated with such application overcome the cost of couple pounds of LPG per week of camping?

It is nice to be able to tune-up through extensive scientific tests if we have time, money and equipment to do so. Why not just insulate with basic method, and let's go camping. And while I truly respect and admire Zeppelenium's knowledge in that field, not all of us can take the insulating of the trailer to that measure. Even if I was able do do so, how much is there for me in return? I do not intend to ever camp in a 120 degree desert heat because I could not stand to walk out into it anyway. For those who do, there just may be a valid reason. Please remember, I do not intend to disagree with the scientific measures of gain, it is ONLY my sensible opinion. Thanks, "Boatdoc"

That is why I put my ideas out there first, to get some feedback. I am not sure of anything I do except for that the fact that I will make misstakes. Besides, if I do everything correct what will some poor sap, I mean, restorer, do 50 years from now.

[boatdoc]

Hi Zep; You are again on the money. Dense and impervious to UV's tent over your AS will stop lot of radiant heat along with ultraviolet gamma ray's. It is the cheapest form of additional insulation from the sun. But, on the other hand, you will still have contact transfer to contend with in ribs and windows. Thanks, "Boatdoc"

[malconium]

I have occasionally given some thought to the idea of having a roll up or fold up awning that covered over the top of my AS as well as extending out over one or both sides. Of course the AC unit is in the way a bit for what I had in mind but that could be dealt with I guess. Perhaps it would be possible to combine Zeps idea of a car cover type of unit with a simple framework that actually mounted on the roof sort of like a luggage rack.

Malcolm

[slowmover]

Spray-on insulation was used by STREAMLINE Travel Trailers through end-of-production in 1974 or so.

Streamline Trailer Brochure

An expanding urethane foam.

Only notes I've seen about this is that over time it tends to crumble (with what effects I don't know).

[C Johnson]

Originally Posted by malconium

I have occasionally given some thought to the idea of having a roll up or fold up awning that covered over the top of my AS as well as extending out over one or both sides. Of course the AC unit is in the way a bit for what I had in mind but that could be dealt with I guess. Perhaps it would be possible to combine Zeps idea of a car cover type of unit with a simple framework that actually mounted on the roof sort of like a luggage rack.

Malcolm

Now that is a good idea. If you could take the idea of the pop-up dining canopy and apply it to fitting over and attaching to an Airstream that would be a good idea. Especially if you could get it to fit into a bag like the canopies. You wouldn't need it every time but, when you did you would have it and it wouldn't take up that much space. hmmmmmm...........

However, at rallies, I don't spend much time at all in my trailer. So maybe that cost would be prohibitive.

Interesting idea though.

FWIW, I put all new fiberglass insulation in my Caravel and in cold weather it is quite warm inside. But, during warm weather it doesn't seem as effective and that is where I think he is going with this study here. If and/or when I do another I am keeping a close eye on his test results, as any novice restorer should.

Kudos to Zep for taking the time to study the differing effects of various insulating methods for our Airstreams.

[Zeppelinium]

I'm still taking data, but the canned foam so far doesn't look at all that spiffy.

First, it's not that straightforward to make the panel. It takes some care to get a nice uniform load of foam into the space. You'd be surprised how voids between the "tubes" of foam tend to remain, albeit smaller, once the foam expands. Second, the solid foam that makes up the edges of the panels and the aluminum panel itself are impervious to moisture, so the humidity that the foam requires in order to cure, can't get to the interior of the foam--at least not very fast.

Here's what the first foam fill looked like before I trimmed it.



Here's what I found--a large gooey cavity. This cavity would have never filled in, regardless of how much water vapor eventually crept inside.



There's no doubt that I got the first layer of uncured foam too thick. But I think this will be a typical installation problem, not to mention that I put this in horizontal and most Airstream installation will be vertical or nearly so. I think a temporary inside skin of some kind would be required in the vertical installation case, which would further impede the flow of moisture into the foam. See below for manually adding water to the mix.

This tells me that filling large (say bigger than about 1/2 to 3/4" thick) cavities requires several passes hours apart. If you fill a cavity from a hole (that has aluminum on both sides) would require even longer intermediate cure times.

I went back and sprayed the gooey hole with a mist of water, then filled it again with foam and sprayed that with another mist. After a couple hours I misted the whole thing again. The result was a good, solid foam pack.

When I trimmed the second time, I found voids of dime to quarter size, which I filled with small squirts of foam from the can. Then I sanded that face down flat and glued on the second panel.

I'm still working the data, but it doesn't look exceptional for the canned foam. The first numbers for the canned foam panel are good, but not obviously better than glass mat or Prodex. It'll be a few more days before I enough data confidence to post, but I thought these early installation observations might be helpful.

Zep