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Old 10-15-2017, 11:46 AM   #1
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What is the best R value insulation for a winter Airstream restoration?

Vintage Airstreams come with fiberglass insulation, but what is the best R value that can be achieved from a renovated Airstream? I would imagine that some kind of closed cell spray foam would be the most efficient at around R-6 per inch thickness. Does anybody have experience insulating with other materials?
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Old 10-15-2017, 12:04 PM   #2
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Welcome to the AirForums!

As a general rule, probably the best insulation material would be a flexible closed cell polyethylene foam (like the middle layer of Prodex), in terms of R-value per inch of thickness. You can get polyethylene foam in thicker sheets than you can get Prodex brand, and a lot cheaper besides.

You'll lose more heat through the windows than you will through the trailer skin, all things being equal, unless you're willing to insulate the windows as well. Clear bubble wrap allows light to shine through the windows, and provides some insulation. Reflectix provides slightly more, and Prodex provides more still, but both Reflectix and Prodex will block all light and turn your trailer into a cave.

There are alternatives to closed-cell polyethylene foam that provides similar R-values for the walls. Mineral wool batting is one such. But for ease of handling and placement, it's hard to be closed-cell foam.

Some people swear by blown-in foam, but I'm not a fan of the stuff. It's hard to apply it in a uniform thickness, for one thing.
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Old 10-15-2017, 12:22 PM   #3
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Welcome. 1.5" walls don't offer much room to differentiate between spray foam, rockwool, fiberglass, cotton, etc. There just isn't enough space to make that big of a difference. I used rockwool because it's easy to work with.

I think the best way to make a big difference is to add a thermal break between the ribs and the interior skin. That way, less heat is getting conducted straight past your insulation through the ribs. I used double-stick foam tape with some sill gasket stuck to the inside for extra thickness. Some folks just use the foam tape.
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Old 10-15-2017, 12:31 PM   #4
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Thanks for the info. Polyethylene sheets do seem less messy to install than spray foam. As far as the windows go, I would definitely want to insulate them in a Michigan winter. Bubble wrap is a great idea because I would still want light to pass through. Would bubble wrap be better than plastic window sheets taped over the windows?
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Old 10-15-2017, 12:33 PM   #5
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Would bubble wrap be better than plastic window sheets taped over the windows?
No reason why you couldn't do both, making a sandwich with bubble wrap in the middle.
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Old 10-15-2017, 12:39 PM   #6
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Yes there is so little space between the exterior skin and the interior skin... I am wondering what the best case scenario could be in terms of R value... The ribs do seem like a weak point for conductive thermal bridging too. While the interior metal skin is off, that's a good idea to insulate the ribs with foam tape for a thermal break. I was thinking about using heavy wool blankets behind the interior metal skin as a thermal block, to stop heat from conducting out of the ribs...
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Old 10-16-2017, 09:01 PM   #7
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Wool, no

I doubt wool would be as insulative as rock wool or fiber glass and would be much heavier. Plus wool feeds insects so you would need to load it up with something like borax or boric acid.
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Old 10-16-2017, 09:08 PM   #8
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Is there anyone who had a professional company spray with closed cell on the forums? A person could get an r-10. I had my attic and basement done in my house it was pricey( $1 persqft per inch) but I love it! I'd contemplate if I had the cash but I'm still working on the house
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Old 10-17-2017, 06:48 AM   #9
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I doubt wool would be as insulative as rock wool or fiber glass and would be much heavier. Plus wool feeds insects so you would need to load it up with something like borax or boric acid.
I ment to use wool as an extra layer, in addition to something like spray foam or fiberglass batts against The exterior metal skin. The wool could just act as an extra thermal break on the metal ribs, so that the heat doesn't conduct from the interior metal skin out to the metal ribs... somebody suggested to use foam tape as a thermal break for the ribs, I think that's a good idea. But, I didn't think about wool feeding insects though, that would be really bad!
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Old 10-17-2017, 06:53 AM   #10
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Originally Posted by MilesOfRoses View Post
I ment to use wool as an extra layer, in addition to something like spray foam or fiberglass batts against The exterior metal skin. The wool could just act as an extra thermal break on the metal ribs, so that the heat doesn't conduct from the interior metal skin out to the metal ribs... somebody suggested to use foam tape as a thermal break for the ribs, I think that's a good idea. But, I didn't think about wool feeding insects though, that would be really bad!
Just to be clear, are you both talking about lamb's wool, or mineral wool? Mineral wool insulates somewhat better than fiberglass of the same thickness, and doesn't attract insects.

Given that your walls and roof are only about an inch and a half thick, you don't really have room for multiple layers of insulating material anyway.
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Old 10-17-2017, 06:57 AM   #11
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Is there anyone who had a professional company spray with closed cell on the forums? A person could get an r-10. I had my attic and basement done in my house it was pricey( $1 persqft per inch) but I love it! I'd contemplate if I had the cash but I'm still working on the house
Well as far as I know, airstreams don't have as much space between the interior skin and exterior skin (1.5 inches ) to accommodate as much insulation as an attic of a regular house. But closed cell spray foam is very efficent at around R-6.5 per inch, so I would think you could get a maximum of R-9.75 in an airstream with closed cell spray foam.
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Old 10-17-2017, 08:22 AM   #12
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I researched this topic far too long when rebuilding my trailer. The conclusion I came to was that really, regardless what you put in that space, your best hope is to get around R6-7. Maybe there is some kind of space-age nano-sphere stuff out there, but, as posters have pointed out above, the windows and ribs are going to negate whatever extreme measures you take.

End of the day, these trailers are really not designed to be lived in full time in the depths of winter. Keeping them hot (or cold, for that matter) is more a matter of brute force than anything. If you have a big enough furnace, then you can fill the walls with whatever is cheapest, in order to offset your propane/electric bill.

There are some threads on here about making a trailer winter-liveable. Try doing a google search from outside the forums for terms like "airforums winter living", and you should get some hits.

good luck!
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Old 10-18-2017, 04:51 PM   #13
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End of the day, these trailers are really not designed to be lived in full time in the depths of winter. Keeping them hot (or cold, for that matter) is more a matter of brute force than anything. If you have a big enough furnace, then you can fill the walls with whatever is cheapest, in order to offset your propane/electric bill.

There are some threads on here about making a trailer winter-liveable. Try doing a google search from outside the forums for terms like "airforums winter living", and you should get some hits.

good luck!
Yes it seems like trailers will always have limited insulation space, no matter the type of fancy material is used.

I wonder if anybody has experience heating a trailer using "passive solar", as in parking facing the sun during winter to warm the interior a little bit. I know cars heat up that way in winter, so why not a trailer?

Thank you, I will look through the old threads about winterizing.
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Old 10-18-2017, 06:37 PM   #14
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Make sure the skin inside the walls is clean to reduce heat radiation. Make sure what ever you use that you fill all voids. I would use what is easiest to do good job. I wonder if it is a good idea to put a less than rigid layer in between the skin and ribs. Seems to me it would allow some small amount of movement. Maybe it does not matter. Maybe put a layer of epoxied carbon fiber as a break on the ribs. Remember in the winter you are trying to prevent heat loss. Inside the trailer make sure cabinet doors close as tightly as possible. Close your curtains when you don't need to see out. Try to make the heated space as small as possible. Do not use your room heat to keep tanks warm by leaving doors open. Way to much heat loss. Buy tank heaters. Best to keep your space sealed. Fill in space next to walls that are not being used and if hidden fill with insulation of some type.
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Old 10-18-2017, 06:44 PM   #15
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Inside the trailer make sure cabinet doors close as tightly as possible.
Actually, don't. Leaving the cabinet doors ajar allows heat into where the freshwater plumbing is (keeping the tanks warm with tank heaters doesn't help if the pipes freeze).

If you're camping in a winterized Airstream and using bottled water exclusively for all sanitary and drinking purposes, then sure, close the cabinet doors tightly to reduce the volume to be heated. Otherwise, no.
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Old 10-18-2017, 08:24 PM   #16
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Hofarc of Santa Barbara promotes an updated spray foam as best :

https://hofarc.com/7-advantages-to-s...am-insulation/

Cost is no object applications.
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Old 10-20-2017, 06:09 PM   #17
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Actually, don't. Leaving the cabinet doors ajar allows heat into where the freshwater plumbing is (keeping the tanks warm with tank heaters doesn't help if the pipes freeze).

If you're camping in a winterized Airstream and using bottled water exclusively for all sanitary and drinking purposes, then sure, close the cabinet doors tightly to reduce the volume to be heated. Otherwise, no.


Good point
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Old 10-20-2017, 08:21 PM   #18
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...as posters have pointed out above, the windows and ribs are going to negate whatever extreme measures you take. .



good luck!
I agree 100%

The difference between the 'best' insulation and the worst could be overcome by a single $15 120v cube heater
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Old 10-20-2017, 08:54 PM   #19
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Hi

The inner skin and outer skin are bridged by the ribs. That's a lot of thermal transfer. "Best" would be to seal off the area and pull a vacuum. That's going to be a bit complex. The previous post about "R6-R7" may be optimistic. It implies you might get a 15% improvement. I doubt the delta from best to almost nothing is 15%.

Simple answer: Set up to skirt the bottom of the trailer when you are parked. That will help your tanks and pipes. Compared to who knows what it will give you a few percent improvement in power needed.

Bob
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