Painting airstream red!

[Over59]

The question is what effect the outside treatment has on the inside air temperature and felt heat (radiation from interior panels). The effects could be demonstrated with soup cans inside soup cans. Put a black object in the inside and measure it's infared heat and the air with an instant thermometers placed in the can though a hole. The interior skin is going to be a reflector as well of the heat radiated to it from the exterior panel. So we have not one but four surfaces to consider with four states each. Thats..... 4 x 3 x 2 combinations or 24 x 2 cans for 48 cans before variations to the space between the cans, ie bubble wrap, glass, foil layers, air. I'll start collecting cans but it will take awhile. Meantime I think I'll take Andy's conclusions and leave it (the AS) as is and park under trees.

[malconium]

I was able to assemble my test panel over the weekend and run some preliminary temperature tests today. Please refer to the attached photos to see what the panels look like. The test panel was built out of 2x2 and 2x4 strips to simulate the 1-1/2" thick walls of an AS. There are 5 cavities in the test panel. The cavities are constructed as follows:



1. Plain aluminum top - fiberglass insulation - plain aluminum bottom

2. Aluminum top painted white - fiberglass - plain aluminum bottom

3. Aluminum top painted red - fiberglass - plain aluminum bottom

4. Aluminum top painted with black rubber coating on bottom - fiberglass - plain aluminum bottom

5. Plain aluminum top - reflective foil insulation - plain aluminum bottom



Andy at Inland supplied the first 4 top test panels and the fiberglass insulation and I supplied the rest of the materials and the labor to build the panel. To install the foil insulation I used some 1" wide strips of foam insulation around the edges as spacers to hold the foil about1" away from the outside (top) skin. The foil has a blue plastic coating on one side which I left up so it would show better in the photos.



I just barely was able to squeeze in some preliminary tests before the sun went behind the house and the trees along the back of our property here. The ambient air temperature was only about 75 degrees too. The weather report is calling for a high of perhaps 85 degrees tomorrow and sunny weather. I hope to be able to get some readings with the sun more directly overhead. Today's quick tests were at about 4:15pm and you can see from the shadows in the saw horse photo that the sun was definitely not directly overhead. Also note that I did not put any enclosure around the bottom of the panel as was suggested earlier in this thread. I have not made up my mind whether that really matters or not in the testing.



To run the tests I set the panel on saw horses in direct sun light. I used a small infrared thermometer to take surface temperature measurements on the top skins (exposed to the sun) and the bottom skins. I took the readings a couple of times over about a 10 minute period with roughly similar results. Here is what I found (the readings are in degrees F):



Panel Type Plain White Red Black Foil

------------------------------------------------------------------

Top Temp 79/81 90/89 101/98 78/75 71/68

Bottom Temp 104/97 89/82 90/87 81/81 91/88



I think the preliminary results are pretty interesting. If the results continue to follow the same general trends that I saw in the above tests I would be inclined to conclude the following:



1. The plain aluminum surface did not collect as much heat as did the white and red surfaces (we expected this from Andy's tests). This is either because the aluminum is reflecting better than the painted surfaces or maybe even because it is conducting the heat to the inside of the wall faster.

2. Any kind of paint or coating on the raw aluminum surface seems to reduce the amount of heat that actually gets transferred through the test wall panel. Notice that the bottom temperatures for all the coated panels are lower than the bottom panel for the plain aluminum test.

3. Putting a coating on the inside of the wall panel and leaving the plain aluminum on the outside seems to be a lot better than putting a coating on the outside. Note though that the white coating was paint not a thicker rubbery coating.

4. Painting an AS red doesn't actually seem to be all that bad of an idea. Evidently while the paint does absorb more heat it also seems to act a little bit as an insulator to the aluminum underneath it slowing down the transfer of heat through the wall.

5. The reflective foil seems to work somewhat better than the fiberglass insulation. The interesting thing is that the foil panel top sheet is not as shiny as the plain aluminum one. I think the thickness is the same but the aluminum type might be different. Andy - what type of aluminum did you use for the top panels you sent me? My foil top panel and all the bottom panels are 5052-H32 0.025 thick.

6. The best combination might very well be a rubbery coating on the inside of the outer skin and foil insulation in the cavity. I might take the plain aluminum panel of the foil test off and add a coating on the inside to test this further.



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.



Malcolm

[Over59]

Nice science project. Is the foil bubble wrap or aluma foil. I also don't get the shiny stuff between the sheets working like that except that it must reflect what would otherwise heat up the interior panel so the only heat that makes it to the interior panel has to get there by conduction. It would be interesting to create a similar air barrier from another material and see if it works as well as the foil, like plastic sheeting, or painting the foil black. It does look like inside coating, airspace, foil, foam board would make a great wall, with alot of work. To bad that fancy space stuff is so expensive.
I appreciate your efforts as I will be need to insulate the Bat Cave. How would it look if I put it all back together, drilled some holes and used cans of foam....blumpstream...

[malconium]

The foil I used is Reflectix brand that I bought at Lowes. What I bought came in a 4' wide roll. It is reasonably stiff too. I don't anticipate having all that much trouble installing it using foam strips as spacers to keep it suspended between the inner and outer skins so that there is a good air gap on both sides. The foil works so well mostly because it reflects the radiant energy back at the top skin rather than allowing it to radiate through. The bubble pack also provides a thermal break that helps keep the heat from conducting from the top side of the foil to the other side.

Malcolm

[87MH]

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.

[silver suz]

My hub has come up with a system of 2 aluminum double bubble layers, seperated by thin strips of styrofoam insulation. (junk left in the loft of the barn) between the inside aluminum wall and the outside wall. He says the critical things are to put some sort of heat blocking strip on the ribs and to make sure that the aluminum panels are sealed together with alum. tape to make the space airtight. The double bubble stuff is aluminum, plastic bubble material, sheet of aluminum foil, another bubble layer, and another layer of foil. We will use 2 of these separated by dead air spaces. Actually the dead air spaces are the best! He has made a test block to make sure it can fit between the inner and outer aluminum walls. The ribs are the weak spots. I'd still be interested in in the painting of the inside of the outer skin. We figure the more insulated, the easier to keep at the temp, that we want. We will use the foilbacked alum paper underneath the wood flooring (3/4" thick plain white oak), as we have in our house (Maybe it was foil on both sides.) Any appliance that gives off heat will be directly vented outside). Also the roof will be mostly covered by solar panels any way.

[silver suz]

OOPS! to continue. I'm making fabric shutters for the windows with 2 layers of the double bubble stuff inside. A humidifyer will take care of inside humidity. Any comments or faults that anyone can see? Yes, this is work intensive, but this is the man who has replaced almost all the rivets. He loves this kind of detail work- sort of meditative for him. I just have to be very patient, hard for a type "A" personality.. Silver suz

[IceKing02]

Silver Suz,

You meant to say a dehumidifier, did you not? You're making a bid to prevent interior condensation if I read you correctly.
The more that any of these Airstreams are tightened up the more of problem that is experienced with condensation. I've tried holding my breath to prevent this water buildup but have so far awakened unsuccessful...

[Inland RV Center, In]

Silver Suz

Foiled backed anything should not be used on any Airstream or Argosy product, not in the walls, or under the floor.

These areas "must" breathe.

Moisture from humidity as well as cooking gathers in these places. Letting them breathe eliminates any problems.

However, if the breathing is impeded in any way, a collection of moisture will occur, resulting in corrosion within the walls and rusting of the chassis.

Not a good thing.

Andy

[malconium]

Andy,

How do the normally constructed walls breathe? Are there some intentially designed in places for air to go in and out?

Malcolm

[silver suz]

Yes, I meant a dehumidifyer- one large enough to do 3 times the cubic footage of my airstream. My house was specially built to be air tight, and to be able to be totally "shut down" for up to 8 hours in case the is some intolerable smell, product etc that could cause me to stop breathing (I'm mostly used to this life so that stuff like this is "normal" for me. In coming air is normally run through filters before circulating through the house. (we have very polluted air and severe pollens) Also we have a heat exchanger and a de humidifyer. The house is steel framed and sealed with the same bubble pack and foil. I'm making the trailer as an escape vechicle that is safe for me, so we are kind of imitating the house.
However I am extremely interested in any problems this method would cause, after all it's our first attempt. We will have proper venting pipes, but with one way flappers. (No gas or propane in this trailer to worry about) and I'll crack a skylight vent open to get filtered air in.) I was thinking of someone's idea (Malcomium?) of having a small wattage fan blowing through the underbelly for circulation. But I don't understand what you mean, Andy, about "filed back anything". Would you please explain more? Thanks, silver suz P.S. I wouln't need all this support when I get to a clean environment and clear out! But I'm still in the "needing a bubble" stage.

[Inland RV Center, In]

Originally Posted by silver suz

But I don't understand what you mean, Andy, about "filed back anything". Would you please explain more? Thanks

Typo's, typo's.

The "filed" should have been "foiled".

Andy

[Inland RV Center, In]

Malcolm.

Airstream and Argosy trailers "breathe" in several ways, as manufactured.

The underbelly seams are intentially "not sealed" so that it will allow any trapped moisture to escape. As with any heat-cool cycles, depending on the humidity and temperatures, visible moisture will occur. Allowing the underbelly to breathe, allows that collection of water to escape.

The internal walls, simply by their construction, allows trapped moisture to escape. Cooking certainly adds considerable moisture to the interior, as well as the simple cooling effect after sunset.

The ceiling vent gaskets are "open cell" gaskets, therefore they allow breathing as well.

The refrigerator vent, also permits breathing.

Granted, breathing not only allows the escape of moisture, but it also allows it to enter. If the construction methods did not allow any breathing, the moistures to some degree will still occur, but the escaping of them would be trapped, ultimately leading to corrosion and/or rust.

It is the later, that must be considered, and, avoided.

Andy

[Catfisherman]

I am looking at just painting the blue trim and lettering red to help match my tow vehicle and toy...they are both red and silver. I took a photo of the airstream then used the paint program to try and picture what it would look like.

[silver suz]

Well, we painted the inside skin white and for some reason the smell is just not airing out (No insulation in yet) My husband did come up with the idea of using plastic pushpins to keep the foil apart. We will see. Meanwhile things have become so drastic here that we bought a new 2004 CCD with no propane ever run in it. It's pretty tolerable to sit in for a couple of hours with filters running. Havent slept in it yet. Meanwhile the composting toilet is working just great in the barn. No odors. suz

[Zeppelinium]

Malcomium! thanks for all the work. You, Andy, and others are to be highly complimented for taking this on.

I've been studying this thread and have some questions. First, when you did the experiment in post #82, with ambient temps around 75 degrees, you got these results:

Panel Type Plain White Red Black Foil
------------------------------------------------------------------
Top Temp 79/81 90/89 101/98 78/75 71/68
Bottom Temp 104/97 89/82 90/87 81/81 91/88

I don't understand how the bottom temps, the side that was in shade, would be hotter than the sunlit side (as it is in three out of five cases above).

It also seems to me that without some mechanism for creating a delta T between the two sides (enclose the shaded side in a volume with thermal mass or air conditioning, similar to the suggestion to put the test panels in Andy's window), there wouldn't be any (OK, there would be some just due to the heat absorbtion of the top panel, but it wouldn't be as strong as you would find in the difference between the inside and outside of a normal trailer) thermal transfer forcing function, so the heat flow from the "hot" to "cold" side would be small compared to the conduction/convection of the ambient air.

The other thing I am missing is any discussion of the effects of emissivity versus reflectivity. This applies in two areas. First, in measuring the temperatures with non-contact thermometers, they see total IR, which would be a combination of both the emissions from the surface and the energy from reflection, so it seems to me that the temperatures of the panels should be measured by shielding them temporarily from direct sun radiation and then quickly taking a measurement, in order to get true surface temperature.

Second, the reflectivity of the white elastomeric coating is the primary thermal feature when it's on the outside (top), but its emissivity is the primary feature when it's on the bottom (inside). Oh, plus conductivity, which applies in both cases. Seems to me you'd want high reflectivity if it was outside and low emissivity if it was inside, so maybe white is really optimal for both surfaces (actually, gold is optimal for IR reflectivity, but I think it has to actually be gold, not gold color--ouch--and I assume white is low emissivity because black is generally high emissivity, but performance in the visual spectrum is no predictor of IR performance).

Have there been any more tests?

[Foiled Again]

Originally Posted by Condoluminum

Oh My...

Please run to an Army Surplus store, buy a military Flak Jacket, and strap it on... You are likely to receive some very passionate messages about your idea to paint the Airstream red... ( I can hardly wait..)

I was just glancing at my latest Blue Beret and on the back inside cover there was an Argosy painted like a garden. Sort of a "by the time we got to Woodstock" look.

It's your Airstream, and you can do what you want with it, however, once painted (once SANDED) it will have to be painted forever. Your resale prospects would probably be nil once you paint it. About six months ago I saw an Avion on eBay that had been beautifully restored, but was painted bright yellow on the outside. I don't think it ever got a bid.

Some folks with damaged skins, or with Argosies have painted them silver, so it can definitely be done. If I were going to paint one, I'd buy an Argosy and paint it, as that won't damage the value that much.

Have fun whatever you do, just think it over a bit before you make a final decision.

Tin Lizzie

[malconium]

Originally Posted by Zeppelinium

Malcomium! thanks for all the work. You, Andy, and others are to be highly complimented for taking this on.

I've been studying this thread and have some questions. First, when you did the experiment in post #82, with ambient temps around 75 degrees, you got these results:



I don't understand how the bottom temps, the side that was in shade, would be hotter than the sunlit side (as it is in three out of five cases above).

It also seems to me that without some mechanism for creating a delta T between the two sides (enclose the shaded side in a volume with thermal mass or air conditioning, similar to the suggestion to put the test panels in Andy's window), there wouldn't be any (OK, there would be some just due to the heat absorbtion of the top panel, but it wouldn't be as strong as you would find in the difference between the inside and outside of a normal trailer) thermal transfer forcing function, so the heat flow from the "hot" to "cold" side would be small compared to the conduction/convection of the ambient air.

The other thing I am missing is any discussion of the effects of emissivity versus reflectivity. This applies in two areas. First, in measuring the temperatures with non-contact thermometers, they see total IR, which would be a combination of both the emissions from the surface and the energy from reflection, so it seems to me that the temperatures of the panels should be measured by shielding them temporarily from direct sun radiation and then quickly taking a measurement, in order to get true surface temperature.

Second, the reflectivity of the white elastomeric coating is the primary thermal feature when it's on the outside (top), but its emissivity is the primary feature when it's on the bottom (inside). Oh, plus conductivity, which applies in both cases. Seems to me you'd want high reflectivity if it was outside and low emissivity if it was inside, so maybe white is really optimal for both surfaces (actually, gold is optimal for IR reflectivity, but I think it has to actually be gold, not gold color--ouch--and I assume white is low emissivity because black is generally high emissivity, but performance in the visual spectrum is no predictor of IR performance).

Have there been any more tests?

The only reason that I can think of why the bottom side would be hotter than the top side would be if the cavity somehow stores up heat. Essentially in the same way that your car gets hotter on the inside when the sun is shining on it.

I do agree that the tests as I did them do not totally reflect (pardon the pun) the reality of an actual airstream installation because nothing is "inside" the trailer. I was not really attempting to do a totally rigorous test but was more interested in a sense of relative difference in the approaches which I think I achieved. It also would appear that since there is a marked temperature differential in my tests that the heat transfer through the panels seems to be more effective than the transfer by ambient air around the panels. One thing that I thought I could do would be to find something like a large cardboard box to mount the panel to. That would allow me to create an inside that was more isolated from the outside.

In general I still think that the tests indicate that we want an outer surface that is as reflective as possible and a skin that is as non-conductive as possible. Shiney aluminum seems to be pretty good at the first but not so good at the second.

When the weather improves around here I would be willing to do some more tests. I still have the panels and the temperature guage. I would love to hear from more people about whether or not they feel more tests are in order and what they would like to have tested. Perhaps those of us that are interested in this topic could colaborate a bit and come up with some testing scenarios?

Malcolm

[Inland RV Center, In]

Paula.

Painting an Airstream trailer, metallic silver, based on my almost 40 years experience, does indeed have an effect on it's value.

The value substancially "increases", simply because if done properly and with first class materials, waxed once a year or so, the life expectancy is at least 20 years or more.

Many of my old paint jobs are still running around from over 20 years ago, that still look great.

Most Airstream owners know that plasticoat on the older coaches is good typically for 3 to 4 years, depending on a number of conditions. They then would be confronted with either replasticoating or polishing the trailer, which in itself becomes a headache, since it must be waxed very often.

If however, someone uses a far out paint design, or poor preparation or materials, then your correct that the value will more than likely decrease.

The latest plasticoat that the factory is using, seems to be holding up far superior to the older material.

However, time, as always, is the real test.

Andy

[Zeppelinium]

Originally Posted by malconium

When the weather improves around here I would be willing to do some more tests. I still have the panels and the temperature guage. I would love to hear from more people about whether or not they feel more tests are in order and what they would like to have tested. Perhaps those of us that are interested in this topic could colaborate a bit and come up with some testing scenarios?

Malcolm

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 and some small distance under the plate 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 will do all the above. Need to have someone else build and provide test panels. I suggest about 16" 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.

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. We'll need to establish a standard size and thickness (1-1/2", right?) if there is a lot of interest.