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Old 12-10-2009, 08:16 PM   #85
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thermal break?

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Originally Posted by Bob Thompson View Post
Since there is no way to do the same to the ribs on our trailers, the next best thing is to add a thermal break between the inside skin and the ribs. I think the best product for this would be strips of EVA foam. EVA foam comes in many thicknesses, densities, and toughnesses. Most people know it as the colored foam used in most cheap flip-flop sandals.
I can see that there would be an insulation benefit in separating the interior panels from the ribs, but also wonder if this would weaken the structure due to the extra space that will be created between the two pieces being held together by the rivets. It seems like this would allow for a little more movement between the two pieces, and over time, more sheared rivets.
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Old 12-12-2009, 07:37 PM   #86
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The thermal break could be relatively thin and firm. Some thin, low compression rubber or poly would reduce the metal-to-metal thermal transfer and I don't think there would be enough "flex" fatigue the rivets. Since I'm embarking on the great foam experiment, maybe someone else will try the thermal break thing?
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Old 12-13-2009, 12:44 AM   #87
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Due to the nature of the construction of Airstream, you can't put a thermal break where it truly needs to be, between the outside skin and ribs. I have spent a large amount of time looking into this topic! I am communicating with researchers from the Green Building Council and their data shows that the major problem is lack of "Thermal Block" in most structures. The research I did with a Vintage Airstream is that 57% of the heat loss was through the ribs. A average house has a heat loss of 40% to 48% through the structure of the walls and roof... With a thermal break it is lowered to 10% to 15%! The tests show with thermal breaks on the ribs of the Vintage Airstream the heat loss should be reduced to 20% to 24%. The data shows the best way is to wrap both sides and the inside edge of the ribs with a thermal break before placing any insulation and replacing the inside skin. Wrapping the the sides of the ribs with a thermal break makes the largest difference in the numbers! The 20% could be lowered if the uses of rivets were not used but thats not going to happen. (To make the point of a thermal break one rivet makes a difference!) The other major heat loss area to look at is the floor where it connects to the outside shell. This area needs a thermal break and is over looked by most.
So even with the better R value with the uses of Foam insulation without a thermal break most of the gain is lost!
Further more, the thermal break that I used in the my research is more of the secret than any insulation that can be used. more info and pictures to follow soon!


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Old 12-13-2009, 07:05 AM   #88
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A tremendous amount of heat is lost through windows (up to 40 percent in a home), but I'm not quite ready for the windowless travel trailer.

I like the idea of using environmentally-friendly, updated materials, but I'm not going to go nuts super-insulating the Overlander. Why? The interior of the Overlander only measures a whopping 23' x 8' (or thereabouts). The total living area is around 184 s.f. Our current home has around 3200 s.f. of heated/cooled space. The biggest inherent advantage of an Airstream is that one is heating or cooling a tiny amount of space compared to the average American home.

Again, I hope someone does the thermal break experiment, but it's not in the cards for us.
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Old 12-15-2009, 06:12 PM   #89
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Todd, wouldn't it help a lot to use a thermal break on the sides and interior of the ribs even though you can't do the outside of the ribs?

The other major loss of heat (besides windows) is air infiltration. The belly pan and the holes through the floor seem to be problems that need correction. I have no idea what the inside of the belly pan looks like, but it doesn't look well sealed or insulated to me.

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Old 01-27-2010, 03:28 PM   #90
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Gene,

As it turn out, the folks at P&S installed a thin thermal barrier on the inside of the ribs. I'm looking forward to doing a field test of insulation soon.
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Old 01-27-2010, 03:50 PM   #91
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Quote:
Originally Posted by CrawfordGene View Post
Todd, wouldn't it help a lot to use a thermal break on the sides and interior of the ribs even though you can't do the outside of the ribs?
Gene
I don't think a thermal break would be needed on the sides of the ribs since they only contact the insulation. Wouldn't the thermal break only be needed where the ribs contact the interior panels?
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Old 01-27-2010, 04:32 PM   #92
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Quote:
Originally Posted by DavidsonOverlander View Post
I don't think a thermal break would be needed on the sides of the ribs since they only contact the insulation. Wouldn't the thermal break only be needed where the ribs contact the interior panels?
That's what I meant, though I didn't say it too good.

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Old 01-27-2010, 05:36 PM   #93
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Streamline started using their Insul-XL aerospace urethane spray foam in 1968; our 1968 29' Empress had it. When I took the interior walls off in 2003, I was surprised to find it, because the brochure I had didn't mention it, but the 1969 brochure does. The foam was perfectly intact. There was actually about 1/4" of space between the inner wall and the insulation. I can tell you that the Empress was always warmer than our Sovereign has ever been.

Would the reason that spray foam insulation wouldn't work in the Airstream be because of its semi-monocoque construction?
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Old 01-27-2010, 05:37 PM   #94
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Quote:
Originally Posted by hampstead38 View Post
A tremendous amount of heat is lost through windows (up to 40 percent in a home), but I'm not quite ready for the windowless travel trailer.
Window losses are usually exaggerated, whether intentional, to make a sale, or the passing of "common" but incorrect knowledge.

The only way a home could lose 40% of its heat thru a window would be if there was air continuously leaking around the window, or a large hole in the glass .

Windows tend to average 15% of the floor area of the home. In a 2000 sf home that would be 300 square feet of window. It is much more likely that heat is being lost thru the 2000 square feet of floor, the 2000 square feet of attic or the approximately 1800 square feet of walls.

Granted, Airstreams have a much higher ratio of floor space to windows. And I too would rather pay the extra in heating costs than give up those wrap around windows.

My vote is for a thermal break in the walls and floors as well.
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Old 01-27-2010, 05:53 PM   #95
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Maybe I am biased by the old single pane windows in my first real house. I couldn't keep a candle lit inside on a windy day.

The foam we used is the Icynene MD-R 200. If it doesn't work, we'll find out soon enough because it has been "blown" and the interior panels installed. The horse, my friends, is out of the barn.

As for the Overlander, the thin aluminum shell and the windows are a disadvantage... but with the interior only 23' long and let's say 7'9" wide, we talking about heating or cooling less than 180' s.f. of living area.

One of my (many) silly ideas is to build an "anti-hail" rain/sun fly of sorts using flexible aluminum poles and ultra light material. While this wouldn't help with heating the Airtream, the shade and air space could make cooling the Airstream far easier.

After a year or two of use, I'll report how the insulation is holding up.
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Old 01-27-2010, 06:36 PM   #96
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Window losses in a home would be based upon insulated windows, right? Mine are single-pane aluminum framed, like most on here. They are probably comparable to an opened window as far as insulation factors are concerned.
I have insulated my ceiling vent lids and I made insulated covers for my windows(not for everybody). The difference is staggering. I wouldn't be surprised if it is 40% including the vents.

Rich the Viking

Quote:
Originally Posted by matthews View Post
Window losses are usually exaggerated, whether intentional, to make a sale, or the passing of "common" but incorrect knowledge.

The only way a home could lose 40% of its heat thru a window would be if there was air continuously leaking around the window, or a large hole in the glass .

Windows tend to average 15% of the floor area of the home. In a 2000 sf home that would be 300 square feet of window. It is much more likely that heat is being lost thru the 2000 square feet of floor, the 2000 square feet of attic or the approximately 1800 square feet of walls.

Granted, Airstreams have a much higher ratio of floor space to windows. And I too would rather pay the extra in heating costs than give up those wrap around windows.

My vote is for a thermal break in the walls and floors as well.
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Old 01-27-2010, 07:37 PM   #97
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I have the 96 Airstream construction videotape and it shows thermal tape being applied to the rib before riveting. So, I guess AS's have had it since then.

Foam insulation has been used in Avions since 67.
Also Avion used foam sealant tape as a thermal break.

I have removed one inside skin on mine to trace a leak.
30 years later, foam is solid and firm. Perfect.
Pics included.
Also helps against dents, AS needs that.

If you research the old brochures, Avion and Streamline had a few features AS does not even have today.

Single pane windows in any RV brand will not help with efficiency.

My 2 cents.
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Old 01-27-2010, 09:21 PM   #98
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Talking in my 89 landyacht....

i have about an inch and a half....covering the entire inside shell....sides and ceiling are spray foamed...

when we did a refit i noticed almost none or little powdering....not much as in not a handfull from the whole trailer.... 20 years old...and it looks good to me...

just my 2 cents...
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