Insulation Technology

[BrandonG]

Okay guys help me out. I searched the topic and could not find anything along this polluted stream of consciousness. I am also not sure if this is the place to put this topic, if not, please put me where you think i should be.

In a do of 1" thick coolers that can keep ice in 80 degree heat for almost a week, what can we do to keep our AirStreams comfy. There has to be a better way than the fiberglass insulation.

Has anyone tried bubble insulation, foam or anything else?

how did it work? What are your experiences with this?

I am interested in making my tradewind as eco friendly as possible and would love my bills as low as possible. during the day, when I touch the inner walls, it is downright hot.

what you think?

[VIKING]

Hi BrandonG,
I hate fiberglass. After seeing the old stuff as I removed it I would never use it in an Airstream. It's like a sponge and it stinks after it gets wet and mildew grows in it.
I asked a professional restorer what he was using and he turned me onto Prodex. You can check it out for youself at www.insulation4less.com . You can see some info about it in my blog by clicking on the link below. Feel free to ask questions.
There are lots of ways to go with insulation. Some are now trying a spray-foam insulation in Airstreams. I think the hassels would not be worth it to me, as the wiring would all have to be embedded in the insulation, and the insulation would have to be done in such a way, as to be able to replace the inner wall panels after the insulation was done. Meaning you would have to trim off the excess somehow. I really liked how easy it was to use the stuff I used. It was just a matter of cutting with a straight-edge and a razor knife, and taping it in place.
For more good info go to the search button and enter a google search for insulation, or be more specific if you want more specific information. There have been a few good threads on insulation lately.

Best to you,
Rich the Viking

P. S. I used my Safari at Burningman, in the Nevada desert last August and it kept nice and cool. I have a few tricks to maximize the effectiveness.

[barts]

Originally Posted by BrandonG

Okay guys help me out. I searched the topic and could not find anything along this polluted stream of consciousness. I am also not sure if this is the place to put this topic, if not, please put me where you think i should be.

In a do of 1" thick coolers that can keep ice in 80 degree heat for almost a week, what can we do to keep our AirStreams comfy. There has to be a better way than the fiberglass insulation.

Has anyone tried bubble insulation, foam or anything else?

how did it work? What are your experiences with this?

I am interested in making my tradewind as eco friendly as possible and would love my bills as low as possible. during the day, when I touch the inner walls, it is downright hot.

what you think?

What's very interesting to do is compute the effective R value for the overall structure.... what you'll find is that w/o a thermal barrier between ribs and the inner walls, the ribs act to conduct large amount of heat between the inside and outside of the trailer.

R-value (insulation) - Wikipedia, the free encyclopedia

The effective R value of aluminum is so tiny that even the thin ribs act as a big heat leak. Suppose the ribs are 24 inches apart, and the ribs are .060 thick. The percentage of rib area is only .25%.... but averaging per unit area, and assuming an R value of .00087 h·ft²·°F/Btu for the ribs and 4.6 for the Fiberglas batts (ignoring skins):

BTUs leaked by Ribs/(h °F) = .25/.00087 = 287
BTUS leaked by batts(h °F) = 99.75/4.6 = 21.7

So overall R value is 100/(287+21.7) = .32 h·ft²·°F/Btu

This is better than brick, but not as good as hardwood.
It assumes perfect thermal bonding between skins and ribs, and also other things can go wrong. For example, Fiberglas batts can clump due to water leaks, etc, and R values don't describe radiative heat transfer very well, so adding Reflectex or Prodex (IIRC) can improve matters somewhat, esp. in the desert where skin temperatures get very high.

But one very important step in better insulation is a thermal barrier between the rib flanges and the inner wall.

A recent thread on this....

http://www.airforums.com/forums/f381...ide-63397.html

If one were designing a trailer today, an two piece rib separated by a proper insulating plastic section would help a lot.

- Bart

[mbattin]

How Heat Moves Through Homes - Building Science Podcast | GreenBuildingAdvisor.com

I posted the text, but there might have been a copy write issue...but I think this quote is worth reading the article-
The article goes into details about insulation but it summarizes by stating...

" These tiny bubbles in between the aluminum foil do help the R-value, and you can get as much as R-1 on some of the bigger bubble products. .... NASA uses radiant barriers because radiation is the only way they can transfer heat from them to other spatial bodies. It’s the only mechanism that works. "

This is a great article from a reputable professional building industry source. I subscribe to fine home building that was a link to this blog. Worth a read, and lots more great articles on there...if you dont want to bother the read, they think radient barriers are snakeoil...

[Jammer]

Originally Posted by barts

BTUs leaked by Ribs/(h °F) = .25/.00087 = 287

Bart the R value figure you quote for aluminum is for a thin aluminum skin. The R-value across a 1.5" rib would be considerably higher, probably by a factor of about 100. I can't find an exact figure anywhere. While the loss through the ribs is substantial and poses condensation concerns it does not dwarf the loss through the fiberglass batting.

[Jammer]

Originally Posted by VIKING

Hi BrandonG,
I hate fiberglass. After seeing the old stuff as I removed it I would never use it in an Airstream. It's like a sponge and it stinks after it gets wet and mildew grows in it.

The insulation is not a water barrier. Even if nonabsorbent foam is used, water leaks and condensation will result in mold.

Avion used foam in their pickup campers and probably in their trailers, too. It performed well, by all reports, but isn't necessarily a huge improvement over fiberglass. For restoration it adds complexity since removing the foam, when necessary, is problematic.

[MarkR]

Originally Posted by mbattin

How Heat Moves Through Homes - Building Science Podcast | GreenBuildingAdvisor.com

. . . . . . . This is a great article from a reputable professional building industry source. I subscribe to fine home building that was a link to this blog. Worth a read, and lots more great articles on there...if you dont want to bother the read, they think radient barriers are snakeoil...

I think it should be pointed out that when he was referring to "snakeoil salesmen" he was specifically talking about people promoting the idea of placing Radiant Barrier under a concrete slab.

If done properly, with an air gap and all edges sealed, they can be effective in walls and even better in roofs - especially in warmer climates.
MarkR

[mbattin]

Mark- that is true, but if you take the thought one step further, the AS is a giant radiant barrier, if you want insulation value, go buy bubble wrap, it's cheaper and all you are doing is paying for air with no moisture ( which is much of why what works in space won't work here). I personally think spray products are the way to go long term, but a system needs to be developed to deal with the deconstruction issues ( I thing a building wrap like tyvek or raindrop. Closed cell rigid or spray are the best to resist mold, have better structural possibility and much higher r-value. There are lots of foams out there, the auto industry uses them, and prob the airline as well. There are products like foregone that have a structural rating, that could reduce skin deformation and rivet failure by creating a true stress skin rather than a modified rib/skin composite.
I read another article about radiant bubble wrap that I am trying to find that identified similar issues and essentially mis labeling r-vales.

[bwaysteve]

Bart,After a weekend in ABQ at the resto rally I had an opportunity to check out Uwe Salwender's trailer he brought for demos.He cut 1 in. strips of Prodex and glued inside to the outer skin.He then glued a sheet of Prodex over these strips creating airspace between the skin and the Prodex.He repeated the process giving him two small air spaces in the cavities..
I plan doing it this way.He may have some pics on his site.area63productions.com

[barts]

Originally Posted by Jammer

Bart the R value figure you quote for aluminum is for a thin aluminum skin. The R-value across a 1.5" rib would be considerably higher, probably by a factor of about 100. I can't find an exact figure anywhere. While the loss through the ribs is substantial and poses condensation concerns it does not dwarf the loss through the fiberglass batting.

Hmmm - thanks.... better check my late night calculations.

I find the thermal conductivity of Aluminum to be 118 Btu/(hr oF ft) from this site:
Thermal Conductivity of Metals.

This means a foot square area 1 ft thick conducts 118 BTU/hr. R values are done per inch of thickness, so this means 118 * 12 = 1416 BTU inch/h·ft²·°F.

Units for R is one over this, or .0007062 - similar to the number I calculated earlier. For a 1.5" rib, it would be .001, something I apparently neglected in the earlier calculation. Overall, I think these numbers are close, but it has been 30 years since my heat transfer classes .

As I said, I find the overall calculation a bit dubious, since heat transfer to the inside of the trailer is much more complicated what with sun, wind, etc. However, I can sure find the ribs in my trailer's ceiling on a sunny day, since the outside skin temperature is prob. easily 30 °F above air temp .

- Bart

[BrandonG]

Originally Posted by bwaysteve

Bart,After a weekend in ABQ at the resto rally I had an opportunity to check out Uwe Salwender's trailer he brought for demos.He cut 1 in. strips of Prodex and glued inside to the outer skin.He then glued a sheet of Prodex over these strips creating airspace between the skin and the Prodex.He repeated the process giving him two small air spaces in the cavities..
I plan doing it this way.He may have some pics on his site.area63productions.com

Okay, What was the result"? Did he also at the 1/8 inch spacer between the rib and the inside skin? How much would this change the fitment of the inner skin?

I am doing this research for two projects. My 65 AS and a Container house I have been planning for 2 years. They pose similar problems. Both become ovens in the SE TX summer.

bg

[VIKING]

I forgot to mention, it was Uwe who pointed me to the Prodex in the first place.
I didn't leave a space between the outer skin and the first layer of insulation. In all cases where I have seen a radiant barrier used it was placed against at least one surface. I have one layer against the outer skin, then a 1" airspace and then another layer of Prodex against the inner skins. I have been in my Safari in the heat of summer with NO insulation, and I could only stay in for a couple of minutes at a time. I accidentally reached up to steady myself and touched the inside surface of the outer skin, and left fingerprints burned onto the aluminum. After insulating I could really tell how much difference it makes as far as keeping it cooler inside. I can relax in the Safari now, with it in full sun, and it stays pretty nice.
I also used the Prodex to make window screen replacement panels and to insulate the inside of the ceiling vent covers. Those metal vent covers on the vintage Airstreams were like little radiant heaters in your ceiling. I glued a layer of Prodex to the inside, and then I made a double layer to go onto the vent where the screen is normally placed. I just pull the two handles off, push the insulation layercake onto the handle stems, and push the handles back on to hold them in place.

Rich the Viking

[bwaysteve]

Originally Posted by BrandonG

Okay, What was the result"? Did he also at the 1/8 inch spacer between the rib and the inside skin? How much would this change the fitment of the inner skin?

I am doing this research for two projects. My 65 AS and a Container house I have been planning for 2 years. They pose similar problems. Both become ovens in the SE TX summer.

bg

It did not change the fit as it was just in essence 4 levels of Prodex.Check the Ambassador Redux thread post 48 (there is a pic).Dar Dane used 1 inch strips of styrofoam to separate the Prodex