Insulation for walls

[Germanaussie]

Hi there,
Is there an alternative for fiberglass batting for the wall insulation? I want something natural, but I guess wool will be too fragile with moisture/rot? Polyester batting? What is everyone using these days?
Thanks,
Germanaussie

[Protagonist]

In terms of R-value per inch of thickness, the very best available is Prodex, a closed-cell polyethylene foam sandwiched between two aluminum foil sheets. But you pay through the nose for it. You can get much the same effect for less money by buying closed-cell polyethylene foam without the aluminum foil on both sides. Plus, Prodex only comes in 5mm and 10mm thicknesses. If you get the foam from a different source (if you Google "closed-cell polyethylelene foam insulation" you'll see there are many suppliers) you should be able to get it up to 2 inches thick.

Fiberglass and mineral wool are about the same as each other in terms of R-value, which makes sense because glass is really just a mineral that has been melted and reshaped. But compared to polyethylene foam, it's not even in the same ballpark with regard to insulation value.

[Melody Ranch]

Kapok...an old tried and true insulation...and you have a life preserver too.

[J. Morgan]

Frankly the effect of thermal insulation in an Airstream is in my opinion a minor factor in comparison to the thermal heat sink that the wall structure of an Airstream is.

A fairly effective heat sink even.


1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[perryg114]

I use two layers of RMAX foam with aluminum on both sides. It insulates and reflects heat. It does not hurt to add a layer of radiation barrier(shiny bubble wrap) as well. Radiation barriers work best with an air gap on both sides and performance degrades as the aluminum coating gets dull and dirty. I use two 1/2" layers of the RMAX foam. You can use the shiny duct tape to seal the edges.

Perry

[69Silvrbelle]

I have been looking at using hemp. Seems to have an R value at about 3.7 per inch. Like that it is natural. What do all of you think of hemp as a viable option?

[Thomas31]

Polarfold is what I used in my reconstruction. I t bends both ways to allow use in end cap radius.

[perryg114]

Any of the rigid foams can be cut part way through with a knife and they will fit just about any contour. You would do this on the back side.

Perry

[flygrrl]

I would be leery of using something in between the panels that could absorb water (from a leak, or mouse pee) and rot, there is the critter factor to consider. Fiberglass and mineral wool seem to make comfy homes for critters too. Hmmmm.
Leonie

[flygrrl]

Polar Fold is awesome too, LEED certified, no ozone depleting agents.

[Germanaussie]

A fairly effective heat sink even.


Hi J,
could you explain the thermodynamics of the airstream to me? HOw is it a heat sink? What is a heat sink in this regard?
Thanks,
Fenja

[Germanaussie]

I also looked into Airkrete, not that it would be available here in Australia.
Is any foam that dries into a rigid structure suitable for the movement of the airstream while travelling? Wouldn't it wear out/crumble, especially if it has no outgassing plasticizers in it?
With wool I meant actual sheep wool which is available as insulation batting here in Australia. Sounds better than jeans insulation battens which would get very heavy and moldy when wet.
Oh, it's really difficult to find a non-toxic insulation material!

[J. Morgan]

Originally Posted by Germanaussie

A fairly effective heat sink even.


Hi J,
could you explain the thermodynamics of the airstream to me? HOw is it a heat sink? What is a heat sink in this regard?
Thanks,
Fenja

Aluminum is an excellent conductor of heat, and heat ALWAYS flows toward the cold(er).

The internal and external skins being large pieces of aluminum are good at absorbing and radiating heat, and the main bows, being aluminum are excellent at conducting heat.

Say for example it is 95 degrees outside and 72 degrees inside.

The heat is absorbed by the outer skin. This heat travels very effectively through the skin to the trailer main bow, (i.e. Ribs), where it is soaked in and then transmitted to the interior skins where it radiates to the interior of the trailer.

The all aluminum trailer is not so unlike an aluminum heat sink that fits over your computer processor.

It will work in the same manner to transmit heat out of the trailer in winter.


1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[perryg114]

An Airstream is not the perfect thermal insulator but it is also not the perfect conductor of heat. Putting a thin layer of plastic between the inner skins and ribs will help a lot. The plastic coating over the interior skins helps insulate some as well. Natural materials might be enviromentally friendly but they are going to be heavier and more prone to be disease hazards as the rats and bugs make home in it as well as mold and fungus growth media. Natural products pollute as well since some sort of farming is needed to grow the materials. Farming pollutes the environment. Spray in foam is probably the most R-value you are going to get but at some point what comes through the skins and through the ribs is going to be the biggest issue.

Perry

[J. Morgan]

In my estimation what is lost through the skins kind of makes attempts at uber efficient insulation run up against the law of diminishing returns.

I used regular old fiberglass insulation, but I put wood over the aluminum on my 72, it is notably better at slowing heat transfer than my stock 75.

The forty year old fiberglass insulation I removed was perfectly fine. I was going to have the trailer spray foamed, but no contractor would return my call. In the end I am glad none of them did because the foam I think would have ended up being a PITA.




1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[Germanaussie]

I think I just found the ideal insulation material. Thermacork:
Thermacork
But I guess the price is just too steep.
So are you suggesting I might as well not put any insulation? OR just some plastic foil? I'm taking the fibreglass wool out at the moment and counting the mouse nests! Their urine is eroding the c-frame!
Why is fibreglass wool considered toxic to breathe in when mice apparently made a great living in it?

[rmkrum]

Mice don't live long enough for it to be an issue. People do.


Sent from my iPhone using Airstream Forums

[J. Morgan]

I think that there is little proof that fiberglass insulation is toxic.

I used fiberglass and if I build another trailer I will use it again. Not only is it an adequate insulator, it helps quite a lot with sound transfer.

Another thing I like about fiberglass is that it doesn't really burn or add fuel to the fire.

My trailer had no infestation in the walls, and still, suppose a person uses something else, who is to say that if mice infest, they wont infest whatever is in the walls?

Just sayin....


1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[J. Morgan]

[QUOTE=J. Morgan;1539003]I think that there is little proof that fiberglass insulation is toxic.

http://www.lung.org/healthy-air/home...iberglass.html

In my reading of this text, the only thing that might be toxic in fiberglass insulation is styrene..... Which if present is present in small concentrations.

What is foam insulation made of?

[Wayward]

For remodeling ("green" or otherwise), closed cell spray foam is my first choice, open cell my second. Batt insulation my third.

Comfort and energy saving is not just about R-value - drafts and cold spots due to air leaks at cracks, and from settling of batt insulation, is quite noticeable. On old houses with lots of leaks and previous remodels, spray foam is amazing. No comparison. People notice the differnce just walking in the room after it is done.

If you do the research and ignore the hype and scare mongers, you will find that the new foam products have no out gassing after they cure.

DIY kits are available.

The advantages over any batt product in an RV are even greater.

• good sound barrier.
• fills cracks and crevices
• 100% fill of all open cavities.
• No loss of R-value from "stuffing" fiberglass into small spaces.
• seamless air barrier - eliminate air leaks
• high r-value
• pest barrier and poor nesting material
• will never sag or settle out
• will never absorb moisture or water (any batt product that traps air well traps water well!)
• cost difference over fiberglass is minimal in RV

Adding a thin thermal break on the ribs will help out more.

By using teltale holes, you can even fill exisitng empty wall cavities.
Foam It Green