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Old 07-28-2012, 11:26 PM   #15
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If anyone is interested, I can provide the thermal break material to greatly reduce conduction from the ribs to the inner skin. I have black 1.5mm "extra tough" EVA foam strips with a very aggressive double stick tape applied to one side. This material is used to make grips for windsurfing booms, but it will work great for this application. It will help keep heat from conducting to the interior skin as well as reduce heat loss in winter. Strips come in approx. 6' lengths and can be made as wide as you would like. PM me for more info.
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Old 07-29-2012, 07:48 PM   #16
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I used two layers of 1/2" RMAX. This has bare AL foil on one side and white painted foil on the other. I used the silver duct tape or I think it is called Tuck tape for sealing the edges. I left the bottom unsealed so water leaks can get to the C-channel to some drains. You can probably use another layer of radiation barrier either as the first layer or the last layer. The foam will conform to the curves if you slit the back side with a utility knife. You can cut out holes for things like tail light etc and use one layer in places like that. Bob's idea about the foam tape on the ribs between the ribs and skin is not a bad idea but I don't know how that will effect the fit of the panels. You can cut the stuff a little big and it holds itself in pretty good but the tape does not hurt. I did not use radiation barrier on the side walls since most of the heat comes through the roof. Painting the roof white is probably going to save you the most in the summer.

Reflective window tenting will help with the heat coming in the windows. You might be able to use radiation barrier to make window covers or mount that stuff on the roll up shade rollers. You might need the non-bubble wrap rad barrier for the rollers. Awnings will help if you have them.

Perry
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Old 07-29-2012, 07:58 PM   #17
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Originally Posted by perryg114 View Post
Probably the spray foam is going to be the best insulation for the thickness. It does have some drawbacks. If you have a leak the water gets trapped in there and if you have to fix something you have to tear out all that foam to get to it.
There are two types of spray foam in common use for home construction. 1/2 pound, or open cell, and 2 pound, or closed cell. The former will absorb water, while the latter won't. The closed cell foam doesn't require the application of a vapour barrier. As for wiring, I'd be inclined to install metal conduit through which to pull wire, if I were to use a spray foam insulation.
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Old 10-13-2012, 01:38 AM   #18
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Paint

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The white and the aluminum absorb about the same amount of heat from the sunlight but the emissivity is higher in the white paint so it radiates the heat much better than aluminum. I have measured these properties before. The absorptivity is the amount of heat energy absorbed from the sun which is mainly visible light. This is about 90% for white paint and polished aluminum. The emissivity or IR reflectance of aluminum is probably not very good. The emissivity of white paint is better and that is why it runs cooler. It radiates more of its heat energy away. See this table. It is the ratio of these two values that determines the heat that goes into your trailer. Convection plays a part as well but the sunlight is a BIG factor. You want low absorptivity and high emissivity.

I use to test space station paints and coatings by measuring these properties and then expose them to UV radiation and measure these properties again after UV exposure. These properties are important for thermal control of spacecraft.

Take a look at this chart of the thermal properties of different materials and paints.

http://www.solarmirror.com/fom/fom-serve/cache/43.html

It is the ratio that makes the white paint so good. The ratio for aluminum is like 3 and the ratio for white paint is like .22. The problem with white paint in the southeast is it mildews pretty fast. The lower the ratio the cooler it is going to run in the sun.

So the best roof coating is white if you can keep it that way. The best wall coating on the inside is bare aluminum in the summer.

The sun puts out about 1400W/m2 in space. By the time it gets through all the crap and moisture in the air, you are probably at about 1000 W/m2 at noon. Multiply by the cosine of the angle of the sun to get the actual value. So that means that you could be getting 1000W of heat per square meter of roof area. 1000W (5000 BTU) is about the heat output of a space heater. So there are several 1000W of heat you have to deal with and you might be able to remove about 10,000 BTU of that with the AC. Windows are a big source of heat absorption as well. Whatever comes in the window is going to end up as heat.

Perry
Perry,
This is what I think I'm going to do:

Spray white paint on interior side of exterior (what would you suggest for a good sealing paint with insulation properties?)

Then I am going to install vertical strips of insulation or foam (approx. 1/2" high x 1" wide) and run them vertically to channel any possible leaks into localized areas. At the bottom of U-channel I'll have weep holes (drilled to 5/32", filled with apoxy, then re-drilled out to #30). Then I will attach first layer of Prodex to foam strips, then install another row of foam strips, then second layer of prodex.
(1/2" strips, 3/8" prodex, 1/2" strips, 3/8" prodex) yielding 1 3/4" total thickness of insulation. I will tape up with aluminum tape, sealing well to keep any convection down. I was also thinking of painting the ends of the ribs, to help reduce conduction. Then install interior skins (which are stripped to bare aluminum).

As for the windows, I'm going to use a double layer shade, which will have a layer of prodex on the inside.


What by the way in the form of Rmax and/or prodex today is receiving the best "bang for your buck" if you will.
For the price, what offers the best insulator properties?

TIMK
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Old 03-24-2013, 07:07 PM   #19
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Geeee. Confused now.. So many ways of trying to seal the heat out lol.. and I live in South Texas too. As a newbe I would hate to spend a few weeks, and $$$, and find out I can't cool the dam thing down :-( ...
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Old 03-24-2013, 09:22 PM   #20
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I have a bright silver painted Airstream and I was surprised to see on the list that bright aluminum paint has a ratio of .80 while real aluminum has 3.0 Makes me glad I chose to paint my trailer, at least from an A/C standpoint.
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Old 03-24-2013, 09:27 PM   #21
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Perry, you might consider white spray-on urethane bed liner for the inside of the outside aluminum skin. If you thin it down a bit before shooting it, it lays down pretty good, reducing the texture you normally see on spray-on truck bedliners. There's a place in Houston that sells the spray-on bedliner in white on Ebay. I bought it and shot my white Tundra's bed with it and it's holding up very well.
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Old 03-25-2013, 10:34 AM   #22
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So may I ask a question then.. In redoing/fixing/upgrading from the factory, or old insulation, how much better does say a 34 ft international with 6 or 7 windows fare in light winder conditions?? ie: say 20's at night and then 40 - 70's+ days... As in parking it in high mountain camp grounds.. If you had to generically put a % number to it.. How much better is the new setup?? Meaning how much %% does the new insulate/work better then the factory/old..

Just trying to get a feel of what upgrades can do as I am totally new to AS.. I am a 50+ year old, Pacific crest trail type of thru hiker, that may gut a AS and make a simple cabin on wheels lol..
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Old 03-26-2013, 07:35 AM   #23
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Look at the threads on winter living for an idea. It much of it also applies to high heat condtions. TT's are really shirt sleeve creatures. Above 80F and below 50F one has to start paying attention to energy through-puts, and how to ameliorate them. Best insulation is the [expensive] step.
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Old 03-26-2013, 11:59 AM   #24
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What's a general $$ amount/ballpark for top quality insulation materials for say a 34 footer.. Just the coat for materials: vapor barrier, insulation, tapes, etc.. Just wondering.. Just a educated guess form someone who has done it!
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Old 03-26-2013, 09:01 PM   #25
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You'll have to define top quality insulation. The best thing you can do is decide what materials you want to use and then price them locally (prices do vary from region to region). What somebody payed in one part of the country, a year ago, may have little resemblance to what you'd pay in your part of the world now.
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Old 03-26-2013, 09:03 PM   #26
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Removing the complete interior, and then the inner skin. And, then, removing the shell from the frame . . . . materials are dirt cheap by comparison to labor.
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