Malcolm,
I think an open air test will minimize the range in test results. I suggest
using a card board box with the top cut out and the panels covering the opening. Limit the airflow. Then take measurements inside the box.
Hey Andy, sorry for second quessing you. We just love to beat a topic to death around here. To us, it is all about fun, joy, and satisfaction. I know
how dedicated you are and how much time a business takes out of your
life. Thanks though for all the time that you give us anyway.
Hey All,
I have an even more better idea. I think the test should be done at a rally with real airstreams ( and an Argosy ) . Line up the trailers facing north ( so they will all get the same sunlight ), and far enough away from each other so they won't cast
a shadow on each other. Use an unpolished AS , a polished AS and a white Argosy.
( and maybe an S.O.B. ) Take similtaneous temperature readings hourly. No awnings allowed.
I have a non contact thermometer RayTek ST20 Pro If necessary I will make arrangements to duplicate the test. BUT! I have a 40' storage trailer with an aluminum top,it is parked in full sun. The front half has been coated with Kool Seal White Elastomeric On a 90 degree day there is a verifiable 10-12 degree temperature difference between the bare aluminum and the coated sections, measured on the inside of the unit.(Eventually I will finish the roof coating) Also FWIW I was playing with the thermometer in my AS the other day and noticed a 8-10 degree temp difference between the center of the interior panels and where they cross the ribs. Guess no one ever considered using thermal breaks? I do plan to coat the very top panel of my AS using the Kool Seal or a similar product. But I want to install my Fantastic fans first.
Aaron
__________________
....so many Airstreams....so little time...
WBCCI #2449 AIR #2495
Why are we in this basket...and where are we going
My guess is that if the kool seal was on the inside of the outer skin that there would be an even better improvement. I still think the reason that a thick white coating reduces the interior temperature is not because white is a better reflecter but because the thick rubbery coating helps stop heat from conducting through the aluminum.
I can easily enough do something like what you suggest. My guess, though is that the readings for this type of test, with the heat source being mostly radiant, that the results might not be that much different. We shall see.
I bought a simple Infrared thermometer for the testing yesterday at Radio Shack. There was an in-store coupon that I found on the internet that gave me a 40% discount. With the necessary 12volt battery I paid about $35 total.
Just waiting for the panels to arrive from Andy now.
My guess is that if the kool seal was on the inside of the outer skin that there would be an even better improvement. I still think the reason that a thick white coating reduces the interior temperature is not because white is a better reflecter but because the thick rubbery coating helps stop heat from conducting through the aluminum.
Malcolm
Malcolm,
That is a part of it too. I work in the commercial roofing industry. One of our most energy efficent roofs is a White PVC membrane, and it gets HOT! on that roof in the summertime from the reflectivity of it, I have never bothered to measure the temps in comparison to some of the other systems. I also know that they are making an energy star rated metal panel also, where the paint is the key to the rating, and suprisingly enough the paint is a matte finish.
Aaron
__________________
....so many Airstreams....so little time...
WBCCI #2449 AIR #2495
Why are we in this basket...and where are we going
The insulation test is not dead, just going slow...
I thought I would make a posting about the insulation test to let people know the project is not dead - just delayed.
I have had to leave home for a 1 week business trip and have not been able to work on it. I do have the panels and fiberglass inslulation that Andy sent me. I also have some aluminum I can use to make inner skins so I can build some sample panels with inner and out skins and insulation.
Hopefully I will be ready to take some measurements within a week or so, weather permitting.
I think when I post the results I will start a new thread that is more obviously about insulation issues so it might be more obvious what it is about.
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.
__________________ Let those who can play, let those who cann't rule.
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:
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):
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.
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...
__________________ Let those who can play, let those who cann't rule.
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.
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Guess no one ever considered using thermal breaks? 
I do plan to coat the very top panel of my AS using the Kool Seal or a similar product. But I want to install my Fantastic fans first. 
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