Inside skin temp to outside skin temp

[DrivingDan]

Hello

Prospective new owner. Question about the skins, inside and outside are aluminum connected by aluminum struts, does the inner skin radiate the heat/cold from the outside? They have insulation but if they are thermally connected via this system then that will work against it, unless they put a thermal insulator between the skin(s) and the struts. Thanks!

[foobar]

Originally Posted by DrivingDan

Hello



Prospective new owner. Question about the skins, inside and outside are aluminum connected by aluminum struts, does the inner skin radiate the heat/cold from the outside? They have insulation but if they are thermally connected via this system then that will work against it, unless they put a thermal insulator between the skin(s) and the struts. Thanks!

During a tour of the Airstream Factory this summer, I observed them placing strips of insulation on the inside edge of each internal aluminum strut in order to break the thermal conductive bridge between the outside shell and the the inside shell.

So they try to reduce the heat/cold conduction from the outside shell through the internal frame and onto the inner shell.

The material probably does not provide a high R-factor but it is better than nothing, lol.

[Bubba L]

We did all we could to lessen thermal transfer at the ribs and stringers. We placed 1/4” Prodex, strips of Foamular, ran the wiring, another layer of Prodex then a 3/4” of Foamular. We painted the edge of the ribs, though I can’t remember what, to lessen the heat/cold transfer. I’ve taken temperatures of the inside skin and outside shell and there was a considerable difference. There are tape and liquid products that can help in temperature transfer when sealing the inside edge of the ribs. Good luck

[DrivingDan]

Originally Posted by foobar

During a tour of the Airstream Factory this summer, I observed them placing strips of insulation on the inside edge of each internal aluminum strut in order to break the thermal conductive bridge between the outside shell and the the inside shell.

So they try to reduce the heat/cold conduction from the outside shell through the internal frame and onto the inner shell.

The material probably does not provide a high R-factor but it is better than nothing, lol.

That’s great the do some mitigations. It’s diminishing returns with these kinds of things, but putting a insulation strip should help. Do you remember what kind of insulation it was, just foam or some kind of bitumen or rubber approach?

Originally Posted by Bubba L

We did all we could to lessen thermal transfer at the ribs and stringers. We placed 1/4” Prodex, strips of Foamular, ran the wiring, another layer of Prodex then a 3/4” of Foamular. We painted the edge of the ribs, though I can’t remember what, to lessen the heat/cold transfer. I’ve taken temperatures of the inside skin and outside shell and there was a considerable difference. There are tape and liquid products that can help in temperature transfer when sealing the inside edge of the ribs. Good luck

Good to know it works (I’m not doing a fixer though)

[Jcondon]

I have used 1/8” Armaflex tape over the ribs on the inside as a thermal barrier but it is thin. It does help. Anything thicker will cause puckers at each interior rivet. I am building a 1969 Overlander now from scratch and I am making fiberglass composite ribs to cut way down on the heat transfer through the skin. With aluminum ribs the conduction almost negates the insulation value. Even with spray foam.

[Tim A.]

As Foobar points out, a thermal break is placed between the outside skin and the aluminum struts. The aluminum external shell, aluminum struts, and aluminum inner shell are simply the way Airstreams are and always have been built.

There other trailer brands which provide much better insulation and, if the insulation provided by an Airstream truly concerns you, perhaps you should consider one of those brands before you invest your money.

Tim

[DrivingDan]

Has anybody made any measurements - even roughly - between outside skin and inside on a hot or cold day, without AC or heat? Using touch isn’t that good a way to test because metal conducts heat so much better (e.g. a metal surface sitting out feels colder than ambient due to good heat conduction, even though it clearly is at ambient temperature).

[DrivingDan]

Originally Posted by Jcondon

I have used 1/8” Armaflex tape over the ribs on the inside as a thermal barrier but it is thin. It does help. Anything thicker will cause puckers at each interior rivet. I am building a 1969 Overlander now from scratch and I am making fiberglass composite ribs to cut way down on the heat transfer through the skin. With aluminum ribs the conduction almost negates the insulation value. Even with spray foam.

Good solution maybe would be plastic strips (teflon would be ideal but expensive and not necessary). Bendable but non compressible, and you could give it a good consistent 1/4 inch. Just get the width of the structure and cut to length, but you do need to predrill probably.

[uncle_bob]

Hi

All walls, no matter how they are made conduct heat / cold from outside to inside. There is no "perfect wall". The walls in your house conduct heat. The much better built walls in houses in places like Sweden also conduct heat. They just conduct a bit less of it.

The answer for any wall is that if you want to reduce the heat / cold flow, you make it thicker. The stuff typically used for insulation really does not do a lot. It helps some, but doubling the thickness of the wall does more. Taking it up to 4X the thickness and putting supports on each side of the wall does more still. To keep the stressed skin design intact this actually would mean four walls and two sets of supports.

Do the walls get a bit cold when it's below freezing out? Yup, they do. The windows get a lot colder. Do the walls get a bit hot if you are out in the bright sun with no wind at 120F? Yup they do. Open the window shades and you will have a much bigger problem .....

The real question is: does the furnace / heat pump / air conditioning supplied keep you comfortable? Over a reasonable range of temperatures, the answer is yes.

Bob

[Mark of SJC]

"Real World Test"

These trailers really aren't designed to be "four season" coaches. None the less, we took ours to Utah...in late December...and it got down to 14 degrees F.

While I understand your concern about conductivity of the shell, it functioned perfectly fine. It was the single pane windows that were the huge chill factor. (At night, if we didn't put reflective insulation we'd cut-to-fit over them, cold air would sheet off of them like an open freezer door.)

I can say that once we did that, we were very comfortable. The furnace really didn't run as much as I thought it would. The tanks didn't freeze (but the valves did!) and we were there for two weeks.

The other real concern is removing humidity. Between four people breathing and the LP for heating and cooking, the dehumidifier pulled an enormous amount of water out of the air!

We would do it again!

[dsatwork]

Originally Posted by DrivingDan

Hello

Prospective new owner. Question about the skins, inside and outside are aluminum connected by aluminum struts, does the inner skin radiate the heat/cold from the outside? They have insulation but if they are thermally connected via this system then that will work against it, unless they put a thermal insulator between the skin(s) and the struts. Thanks!

You are worrying about the wrong thing, the windows conduct more hot and cold than the walls do. We have been living fulltime in an Airstream since 2018 and have been in every conceivable temperature and conditions. We use Reflectex on all our windows in extreme hot and cold to provide added insulation. Reflectex can reduce the inside temperature by 10 degrees or more and creates a added barrier from the cold as well.

[MySovereign]

...out of curiosity generated by this thread (using laser thermometer):

Sunny day, outdoor temperature @11:30am: 97 degrees
2004 Airstream 22' CCD
AC off, door open (left overnight this way)
Ambient temperature inside (at panel): 84 degrees
Outside skin in direct sun: 122 degrees
Indoor skin at same location: 95 degrees
Outdoor skin in shade: 95 degrees
Indoor skin at same location: 92 degrees

Of course, with AC on it would be completely different.

[2012FB]

Originally Posted by DrivingDan

Hello

Prospective new owner. Question about the skins, inside and outside are aluminum connected by aluminum struts, does the inner skin radiate the heat/cold from the outside? They have insulation but if they are thermally connected via this system then that will work against it, unless they put a thermal insulator between the skin(s) and the struts. Thanks!

Yes, the inner skin radiates the heat/cold from the outside. The wall construction of an Airstream from a thermal insulation standpoint is extremely poor. I have owned two R-Vision trailers and the rigid fiberboard on both sides with insulating foam sandwiched between is far superior to Airstream's Aluminum on Aluminum on Aluminum construction. It is why I ordered two AC/Heatpump units on our 25'. I have considered lining the interior of the bedroom walls with something that would provide an insulating barrier. We have twins and the interior skins are nearly just as cold as the exterior skins in the early morning.

[DrivingDan]

In general - yes I’m an engineer and have rebuilt old houses, I understand much about thermal control. A disease of being an engineer though is that I have trouble buying something something that isn’t designed well, so if AS didn’t take basic preventative measures it would get on my nerves.

Originally Posted by Mark of SJC

While I understand your concern about conductivity of the shell, it functioned perfectly fine. It was the single pane windows that were the huge chill factor. (At night, if we didn't put reflective insulation we'd cut-to-fit over them, cold air would sheet off of them like an open freezer door.)

Good to know, thanks! Yes windows are the weakest link, and without doubled pained there’s little you can do (thermal coatings have some effect but I don’t think it’s large). We don’t plan on a lot of freezing camping but I don’t want to rule it out as it will surely happen.

Originally Posted by MySovereign

Sunny day, outdoor temperature @11:30am: 97 degrees
2004 Airstream 22' CCD
AC off, door open (left overnight this way)
Ambient temperature inside (at panel): 84 degrees
Outside skin in direct sun: 122 degrees
Indoor skin at same location: 95 degrees
Outdoor skin in shade: 95 degrees
Indoor skin at same location: 92 degrees

The definitive answer - hand that man a cigar! The important bit is highlighted, that the inside skin is at ambient. Now that skin is a huge heat sink, so you could argue that if it was transporting heat from one side to the other, it would equally be radiating it away to the inside. But in that case there would be a differential - on the surface it would be hotter than ambient in the middle of the camper. Since it’s equal to shade ambient that tells us that there’s little transfer, unless my reasoning is flawed somewhere.

What led to this is reading somebody complaining of this issue with theirs, and a very unscientific test from a rebuilder in Texas who tried spraying special thermal compound inside. This test you did here looks good to me that the treatment they use is effective, and good to know they were taking care of the issue going at back to at least 2005.

[jeffb831]

Originally Posted by DrivingDan

A disease of being an engineer though is that I have trouble buying something something that isn’t designed well, so if AS didn’t take basic preventative measures it would get on my nerves.

Unfortunately, there are many issues with Airstreams that are head scratchers and don't necessarily follow modern design principals since the trailer has been basically built the same for 80 years.

If your "disease" is as bad as you say (this issue is on the lesser scale of the ones you'll encounter), you'll be stressing over so many things that you won't ever enjoy the trailer.

[DrivingDan]

Originally Posted by jeffb831

Unfortunately, there are many issues with Airstreams that are head scratchers and don't necessarily follow modern design principals since the trailer has been basically built the same for 80 years.

Don’t need to infer too much. Nothing is designed perfectly - I don’t even know what that means since every project is a mashup of yes, historical precedent or legacy design, engineering, marketing and production. All a compromise, but saying that, while there’s a few points that concern me about AS as an engineering solution overall the legacy design looks to me to have more going for it than not.

I’m a pianist and we could talk about the legacy design horrors on the Steinway that they’re stuck with. Those pianos take a lot of work direct from the factory just to be playable. Fortunately with AS the only real legacy is the monocoque aluminum body and maybe the frame (though the metallurgy on both has improved, along with modern paint and clear coat). The rest of the guts have all been modernized from the head (used to be a chamber pot delicately called the “thunder mug”) to the fabrics. Can’t change the guts of a Steinway!

Anyway tldr but there is one other design question I’ll ask in a new thread. Thanks for the kind replies everybody!

[NevadaGeo]

Originally Posted by DrivingDan

Hello

Prospective new owner. Question about the skins, inside and outside are aluminum connected by aluminum struts, does the inner skin radiate the heat/cold from the outside? They have insulation but if they are thermally connected via this system then that will work against it, unless they put a thermal insulator between the skin(s) and the struts. Thanks!

Good question to wonder. Theoretically there is some insulation installed between the panels. There's not enough inches to do much isolation.
On my '78, Outside I've seen 145 degrees on the blue strip, 120 on the aluminum. Inside, 120 or 100 opposite the blue strip, 95 degrees opposite aluminum.
I put the water heater insulation "Reflectix" inside on all my walls, get 85 degrees on the inside of the reflectix. It may look tacky but it's much more livable. Don't paint the reflectix. Had some one do that to me once, it killed the insulation properties and had to replace that with new reflectix. It also helps to isolate the center room for cooling.
One year I left some wine bottles in the under bunk drawers, cold winter froze the wine and pushed the corks out. I had tubs of unusable wine.

[lemley]

Originally Posted by DrivingDan

Has anybody made any measurements - even roughly - between outside skin and inside on a hot or cold day, without AC or heat? Using touch isn’t that good a way to test because metal conducts heat so much better (e.g. a metal surface sitting out feels colder than ambient due to good heat conduction, even though it clearly is at ambient temperature).

I’m out right now. AC running full tilt. All measurements are made in the shade. 1988 Excella. Measurements made about 6” forward and below side bedroom windows. Rear bedroom.

Ambient. 101
Outside skin, curb (sunny)side (in shade). 98
Inside skin, curb side. 88

Outside skin, street side. 94
Inside skin, street side 84

Inside temp. 82

[PC Conner]

Lots of good responses and info (but I didn't read all of them).
My experience is from a 2019 summer trip to Phoenix. We lived in CA high desert and daughter's family in Phoenix. We found a nice RV park 15 minutes from them and planned to leave our small dog at the trailer during the day and bring a grandchild to spend the night in the trailer.
We have 2 AC units.
Temps were in the range of 117 during day with lows over 100 after sunset. Discovered it was much too hot for our dog in the day. Water was hot out of the faucet (a Forum suggestion was to fill water tank and use water from the tank, good idea).
BUT--the inner skin was hot to the touch with both AC units running.
Our solution, don't take AS to AZ in summer.

[DrivingDan]

Originally Posted by PC Conner

Temps were in the range of 117 during day with lows over 100 after sunset. Discovered it was much too hot for our dog in the day. Water was hot out of the faucet (a Forum suggestion was to fill water tank and use water from the tank, good idea).
BUT--the inner skin was hot to the touch with both AC units running.
Our solution, don't take AS to AZ in summer.

Hard to say from that, one is that in those temps the AC is less efficient at dumping heat in an already hot environment. Two is that the touch measurement isn’t useful, since metal conducts heat so well. You have to measure with a surface thermometer and compare to internal ambient. But even given that, with the heat you were experiencing it could be that the two AC’s just can’t keep up with keeping the air and inner shell cool.