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Old 09-27-2004, 09:36 PM   #1
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Insulation - real test results...

There was some discussion started in the thread titled "Painting airstream red!" that resulted in some actual tests of AS insulation with various types of coatings. I started a new thread here because I didn't think it would be at all that obvious from the title of the other thread that there were insulation results there. So take a look if you are interested in AS isulation and maybe we can spin the whole topic off to another thread if that makes sense. Check out the thread by clicking on the following link:

http://www.airforums.com/forum...ad.php?t=13363

Malcolm
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Old 09-28-2004, 06:42 AM   #2
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Copied from "Red Paint" thread.

Quote:
Originally Posted by malconium
There was some discussion started in the thread titled "Painting airstream red!" ....... Check out the thread by clicking on the following link:

http://www.airforums.com/forum...ad.php?t=13363
From above mentioned thread.....

Quote:
Originally Posted by malconium
I would be interested in any comments about the tests and the results. I think I will post a new thread about insulation and refer to this red trailer thread. That way people interested in insulation can find it better.

Malconium -

Thanks for your efforts - and sharing them -- I, also, have been wrestling with the decision of "What to do with the roof". I do not anticipate pulling the interior panels, so my focus is on exterior coatings.

"While you are at it"....could you do a comparison on your test stand with a white elastomeric (Kool Seal) type of coating? - maybe two thicknesses?

I am particularly interested in the Kool Seal "RV Rubber Roof TopCoat White Elastomeric #63-900". The appropriate undercoat must also be applied.....of course, they recommend the undercoat to be applied to existing rubber roofs - you would have to get Kool Seal's recommendation as for applications for RV use on an uncoated Aluminum roof.

It would not surprise me if you would contact the manufacturer at http://www.koolseal.com/contact_us.asp and explain what you are doing, (and how many Forumers could potentially use their product) that they would ship you a quart of both (top coat and appropriate primer) for free.

Looking forward to you next results.
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Old 09-28-2004, 09:14 AM   #3
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IMHO you need to alter your experiment to get a true reflection of AS construction. You are measuring panel temperatures separated by nothing but insulation and air gaps, but the shell has a LOT of ribs, windows, door and access hatch openings, all connected by fairly heavy, extremely conductive aluminum extrusions. Make some 'ribs' and attach the 2 panels together, reinsulate and measure the difference. If you think about how the shell is constructed it is basically a giant heat sink. I have seen bands of frost inside my mh from the conduction of the ribs, the best insulation will not stop this unless the inner skin can be thermally isolated from the rest of the shell.

John
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Old 09-28-2004, 04:41 PM   #4
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Well you've sold me on the foil bubble wrap at least for the domes. I'll glue it to the back of the end cap before putting it back. This should made a nice air space between the exterior and the foil. Only question is whether to paint the interior of the exterior (it would help to have words for this things) black.
Let's us if I buy 6 large cans and 6 small ones I could make 6 mini AS models and...... Glad you're there Malcolm.
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Old 09-28-2004, 05:59 PM   #5
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Only a partial test was intended...

John,

I agree with you that the tests that I have performed do not give the whole picture. They were not actually designed to give the whole picture however. The real focus of the tests as initially conceived was to measure the relative effectiveness of the types of coatings that we were talking about in the thread. I wanted to make sure that we were evaluating the coatings in a context that was more realistic so I came up with the test as performed. I decided to add the reflective foil because I had already decided to go that route and wanted to check to see if it was really justified. The whole topic of insulation and heat loss/gain is a pretty complicated topic. In general it has been my experience that any insulation strategy ends up being a compromise in that you will always have some aspects of any given structure that perform better or worse than other aspects. Things like the windows, doors and ribs that you mention are all good examples of that. In the end the effectivness of the strategy pretty much always ends up being the average performance of the sum of all the parts of the strategy.

I am in complete agreement with you about the desirability of isolating the skins from the ribs to help reduce the flow of heat by conduction. My test indicates that even a relatively thin layer of some non conductive coating can help a lot in this regard. I am giving some thought to putting something on the inner side of my ribs before I put the inner skin back on. I have though about using some type of thin foam tape for example. The problem with any coating I can think of is that it will mask the locations of the holes that the body panels attached to making it harder for me to find the original panel alignments for re-installation. Maybe this is not a serious issue but I am not sure. Any suggestions?

Malcolm
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Old 09-28-2004, 06:05 PM   #6
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Add some spacing to caps...

Over59,

Putting the foil on the end caps before putting them back in is a good idea that I will have to consider myself. It would be good, though, if you can space the foil away from the cap a bit. For best effectiveness the foil depends on an air gap on the side of the foil toward the source of the heat. For the summer time that is outside of the AS. For the winter, however, that will be toward the inside of the AS. That is why I am intending to have about 1/2" air gap on the inside and about 1" on the outside. You might very well be able to do this on the caps by glueing narrow strips of 1/2" thick foam to the caps and then glueing the foil to the strips. Just a thought...

Malcolm
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Old 09-28-2004, 06:26 PM   #7
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YEP! I have noticed it too...

Quote:
Originally Posted by 74Argosy24MH
IMHO you need to alter your experiment to get a true reflection of AS construction. You are measuring panel temperatures separated by nothing but insulation and air gaps, but the shell has a LOT of ribs, windows, door and access hatch openings, all connected by fairly heavy, extremely conductive aluminum extrusions. Make some 'ribs' and attach the 2 panels together, reinsulate and measure the difference. If you think about how the shell is constructed it is basically a giant heat sink. I have seen bands of frost inside my mh from the conduction of the ribs, the best insulation will not stop this unless the inner skin can be thermally isolated from the rest of the shell.

John
But on the hot side of the spectrum. I have a Raytek non contact thermometer and when playin with it in the Airstream one hot summers day Noticed a 10-15 degree difference between the where the ribs bridge the skins and the center between the ribs. Also FWIW the double pain Vista Views were cooler than the single pain....Go figure

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Old 09-28-2004, 06:58 PM   #8
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Quote:
Originally Posted by malconium
The problem with any coating I can think of is that it will mask the locations of the holes that the body panels attached to making it harder for me to find the original panel alignments for re-installation. Maybe this is not a serious issue but I am not sure. Any suggestions?
My inner skins were pretty bad, I wanted to move things around, and I wanted consistent rivet spacing so I made new ones. It also seemed easier than trying to figure how to patch or hide holes I wouldn't use. I put 3/16 closed cell foam tape on the ribs before pop riveting them. The panels pulled up smoothly and it is not noticeable.

I considered what double drilling the ribs would do to strength and don't think it will be harmful. Pop rivets aren't all that strong and the ribs are thicker than the skin, any failure would be in one of them before the rib, most likely the rivet.

OTOH using the original skins I don't see why you couldn't pick up the holes. Use an awl or center punch to pierce the foam and line up the first hole, the others should be in alignment. The foam compresses very evenly and pretty thin, probably not enough to throw the other holes out of alignment even on the curves.

John
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Old 03-16-2006, 09:52 AM   #9
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data logger

I've been using an 8-channel data logger (software is DOS and Forth, not user friendly, but fun--any old astronomers here?) to collect data on the thermal performance of my home and trailers (I was mainly interested in how the various compartments, like the space behind the rear bath, did in comparison with inside trailer temperatures, as the outside temp fell below freezing). It takes about a day to construct the A-D board and check it out. I have 10 or so laptop-like PC-XT machines that I use for the logger (anyone got a crying need for one? They draw less than one amp.), but any computer with a parallel port can do the job. The output is a comma delimited text file that can be imported to Excel.

With 8 channels you can get a pretty detailed analysis of outside and inside ambient temps, skin temps, and thermal conductivity of the ribs, plus samples of several compartments, the most important I think would be behind the bath and under the sink. I intend to tackle this as soon as I get the skin back on my 27' 1972 (with Malcomium's foil insulation) and compare that to the performance of my stock 31' 1975 for this coming summer in the SW dessert. If anyone else wants to tackle this, let me know. I don't have a clue at this point how we'd normalize the data, but if several different insulating methods have been tried, I'd like to compare them.

I'm particularly curious about what we have discovered regarding best methods for underfloor insulation.

Here's some details on the data logger performance:

The data logger uses a Maxim ADC186, connected to the computer via the parallel printer port (+5 and +12 volts are required). The ADC provides 12 bit conversions. When an LM-135 is used as a temperature sensor, temperature is measured with 0.1C resolution. LM-135 accuracy affects only the slope of the temperature equation, so with only a single multiplication/division operation to adjust the slope, a highly accurate system is possible. LM-135 uncalibrated accuracy is generally on the order of 1.5% or better, but can be as poor as 5%. After calibration, long term accuracy appears to be within 0.3F or better.
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Old 03-16-2006, 10:07 AM   #10
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"Malconium method"?

I have looked through all the related threads and I see that foil, supported away from the skins, is a highly effective insulation. However, I don't see any details on whether or not the foil is glued and sealed to the ribs at the edges to create a reasonably air-tight volume. Are the installation details already discussed elsewhere?

What about Andy's comment about foil, breathing, and condensation? Any indication that the "Malconium method" creates condensation or other water vapor problems?

While I'm at it, I'd like to insulate the belly pan with something that's inhospitable to vermin and waterproof. If you put a closed cell foam up against the floor, is there a concern about possibly retaining a thin film of water on top of the foam and against the plywood? If the edges are reasonably tight against the frame members but aren't sealed, would that be enough breathing room?

Someone indicated they would install two layers of foil. Is there any data, subjective or otherwise, on how effective that was?

I also saw that interior skin temps along the ribs was 7-10 degrees different than the skin away from the ribs. Has anyone measured the improvement using either the 3/16" closed cell foam tape or the cork tape (seen in other posts)? Did these methods of insulating the ribs reduce condensation significantly, or change the inside temp (I'm mostly interested in the hot climate results, but the cold climate results should be an indication of similar performance on the hot side, duh).
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Old 03-16-2006, 12:29 PM   #11
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Quote:
Originally Posted by Zeppelinium
......... I'm particularly curious about what we have discovered regarding best methods for underfloor insulation......
I'm planning on using Malcom's foil method as well, provided I can afford it! The underfloor part....I'm going with closed cell foam sheets, the same stuff you see on the outside of new home construction, glued to the bottom of the floor. Or at least that's what I'm thinking of doing. Two reasons. The 3/4" plywood floor is an excellent insulator by itself. We had a walk-in freezer at Scout Camp when I was a kid that was made of wood that would cool to something like -10 degees. The other reason is that the belly pans on the '70's models allow mucho water in and the pink stuff insulation turns into a muddy, wet, soppy mess. I've made conserable effort to keep water out of the pan, but in the event water does get in (it will), I don't want material sittiing in the belly pan wet and potentially ruining all the work I've put into rehabing the frame and floor.

What do y'all think of my plan? Does it make sense? Or am I all wet?

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Old 03-16-2006, 12:58 PM   #12
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Quote:
Originally Posted by Zeppelinium
I have looked through all the related threads and I see that foil, supported away from the skins, is a highly effective insulation. However, I don't see any details on whether or not the foil is glued and sealed to the ribs at the edges to create a reasonably air-tight volume. Are the installation details already discussed elsewhere?

What about Andy's comment about foil, breathing, and condensation? Any indication that the "Malconium method" creates condensation or other water vapor problems?

While I'm at it, I'd like to insulate the belly pan with something that's inhospitable to vermin and waterproof. If you put a closed cell foam up against the floor, is there a concern about possibly retaining a thin film of water on top of the foam and against the plywood? If the edges are reasonably tight against the frame members but aren't sealed, would that be enough breathing room?

Someone indicated they would install two layers of foil. Is there any data, subjective or otherwise, on how effective that was?

I also saw that interior skin temps along the ribs was 7-10 degrees different than the skin away from the ribs. Has anyone measured the improvement using either the 3/16" closed cell foam tape or the cork tape (seen in other posts)? Did these methods of insulating the ribs reduce condensation significantly, or change the inside temp (I'm mostly interested in the hot climate results, but the cold climate results should be an indication of similar performance on the hot side, duh).
You can find some more details about the installation approach that I used along with some photos in the following thread:

http://www.airforums.com/forum...ods-14803.html

I used foam strips around the edges of the cavities to act as spacers to hold the foil in the middle of the cavities. The foam strips are generally tight to the sides of a given cavity and the foil is cut as close as I can to the actual size of the cavity. I glue foam to the outer skin, glue the foil to the outer foam strip and glue the inner foam strip to the foil. The only place where the foam is not tight to the outer sides of the cavities is along the bottom at floor line. I have held the foam back 1/2" or so to create a bit of a channel along the botton. I also drilled holes in the bottom of the wall cavitity and glued screen over them so that there was a path for moisture to get out if any managed to accumulate at the bottom of the wall.

For floor insulation since I am intending to install hot water radient heating on top of the floor I am intending to add a layer of reflective foil on the floor first and put my heat tubing on top of that. I had originally thought of putting a layer of foil under my floor and using some sort of spacer to keep it just below the floor so that I had an air gap between the floor and the foil. The reflective foil seems to be more effective with an air gap and this would provide a little breathing room for the bottom of the floor. In my case I am using Polyboard for the floor so moisture would not have been a problem. I did think though that I might poke a small drain hole in the middle of the foil in each cavity. The slight sag in the foil would cause any moisture to drain toward the hole and out.

I think the idea of glueing foam to the bottom of the floor is a good idea too. The good news is that the floor is the least important place to have insulation so most any solution would work well enough in my opinion. Some forum memebers have even elected to leave the under floor area without any insulation.

Malcolm
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Old 03-16-2006, 01:13 PM   #13
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The following was also posted to "paint your airstream red," but I think I'll confine all my insulation/thermal performance posts here from this point on...

Malcolm,

Wow, I never thought of the "inside of the car" greenhouse effect. Very possible, but it seems that would have heated the top panel, too. I need to think about how we'd design the unassailable experiment.

I think if I use my data logger to watch the temperature profile throughout the day, and build the box you mentioned but connect it tightly to the earth (cut out the bottom of the box and bury the edges a little--good thermal sink, the earth), we could infer quite a bit. Here's a full description:

1. Build said box (box to be insulated with 3/4" foam on all sides and painted white outside) and tie it to the earth-- provide suitable standard hole in top to fit the various panels. Provide temperature sensor in dirt, in the air inside the box, and two more for bottom and top temperatures of the panel. Provide a wind shield around the test site that doesn't shade the box.
2. Provide a "standard plate" that is black and is horizontal, on a pole next to box. Put a sensor on the plate (to get an idea of the sun load) and one some small distance under the plate (shading the sensor) to get air ambient temp.
3. Record and graph the temperatures for 24 hours.
4. Install new panel and repeat.
5. Take a standard reading (24 hrs) on the box with a single sheet of unpolished aluminum to cover the "test hole."

I recognize that day-to-day ambient conditions won't be constant, but by graphing the results (and maybe doing this test for a week, then repeating for all panels) you will quickly see the delta temperatures. I think a lot can be inferred from that.

I volunteer to do all the above, but I would need to have someone else build and provide test panels. I suggest about 16-24" square--how big were the panels that Andy built? I'd like to see a panel with a rib in the middle. I think we ought to also see what happens if you make the panel sandwich without ribs (use foam and glue on the edges) and with ribs (one side, two sides, four sides) to get an idea of what the thermal conductivity of the ribs is compared to the larger area between the ribs. We wouldn't want too much rib compared to surface area--off the top of my head I think the ribs are about 2% of the area along the sides and maybe as much as 5% along the top (ceiling area). Hmmm, thinking about this, one rib down the middle of the panel would probably be more than in a representative trailer. Maybe just a short section would do the trick.

Yo! This is a lot of little pesky panels!! I guess you'd only have to do the rib variations on one panel design, say with fiberglass batts as the standard, since that's what the standard AS comes with.

I wonder if others would like to build panels. We'll need to establish a standard size and thickness (1-1/2", right?) if there is a lot of interest.
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Old 03-16-2006, 01:25 PM   #14
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got bubbles?

hello all you heat seekn', heat avoidn', insulating but not insulting folks....

well the factory is now using foil in the floors...

here is a photo....i offer as proof

taken while in jc.....recognize the aluminum/builder debris....left behind?

seems i heard they were going to start using the bubble in walls as well,

but i don't know if that has started....or been foiled.......

a call to service...or an email to a technical online person type......

might yield info on how they are securing said foil in between ribs...or not

my walls is pink inside.....and i have proof.....

cheers
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