Insulation for walls

[perryg114]

Fiberglass is not toxic unless you breath the dust from it. It is an excellent growth media for mold and bacteria as well as any other batt insulation. It traps odors from same.

Perry

[Lumatic]

Originally Posted by 69SlvrBelle

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?

Cheech and Chong invented this technique
Google Image Result for http://blogs.houstonpress.com/hairballs/drugs-border.jpg

[J. Morgan]

I would suppose that a leak is going to cause issues whether fiberglass or foam is used.

I have seen buildings where the bottom of the roofs have been spray foamed. When leaks happen, and they do, the water emerges no where near the actual leak.

Everything is a trade off in one manner or another.

Then we have the issue of future changes and repairs.....

I am not against spray foam I just don't think it is always the best solution, especially in an Airstream where the insulation is bypassed via conduction through the aluminum structure.

As far as spray foam stopping air infiltration, if the shell of an Airstream is problematic in this regard, there are problems bigger than the choice of insulation is going to fix.

And like I said, trying to find a contractor willing to spray my trailer was problematic, and the kits available for DIY were expensive. By my estimation it would have cost me 3k or more to buy enough product to do the walls of my trailer. Not worth it for my build. That would have been my single biggest expense.


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

[Protagonist]

Originally Posted by J. Morgan

As far as spray foam stopping air infiltration, if the shell of an Airstream is problematic in this regard, there are problems bigger than the choice of insulation is going to fix.

If you plan to use your Airstream in the winter, and will heat with a propane-fueled furnace, then you NEED air infiltration anyway. You're never going to turn your Airstream into a Thermos bottle no matter how well you insulate.

And of course insulating the walls doesn't help you with the door, the windows, the roof vents, the belly pan, the storage compartments, and all the myriad other places where heat can get in during the summer or get out during the winter.

The principle of diminishing returns applies. When you spend more for better insulation than you would spend in propane to heat the trailer without the better insulation insulation, you're wasting money. So my recommendation is, do a good job of insulating, but don't obsess about doing a great job of it.

[Markj55]

Originally Posted by Protagonist

If you plan to use your Airstream in the winter, and will heat with a propane-fueled furnace, then you NEED air infiltration anyway. You're never going to turn your Airstream into a Thermos bottle no matter how well you insulate.

And of course insulating the walls doesn't help you with the door, the windows, the roof vents, the belly pan, the storage compartments, and all the myriad other places where heat can get in during the summer or get out during the winter.

The principle of diminishing returns applies. When you spend more for better insulation than you would spend in propane to heat the trailer without the better insulation insulation, you're wasting money. So my recommendation is, do a good job of insulating, but don't obsess about doing a great job of it.

That's the best advice I've heard yet. I use my AS all seasons... Propane is cheap and if your plugged in, space heaters work great. I've found and sealed air leaks coming in from around the fridge and also up from under the bed via the storage compartment. Fixing those and ensuring the insulation around doors and windows is doing It's job and in good shape.

I'm amazed at what people obsess over.... It's a trailer, a damn good one and it beats the poorly insulated tent I used to camp in 😏


Mark,
The path not taken is the one I take.

[TG Twinkie]

The furnace (if installed properly) will not consume combustion air from within the coach. The combustion air comes from outside. Thus the reason for 2 holes in the skin. One for exhaust and the other for combustion air.
If the combustion chamber is faulty CO could be emitted into the coach. CO detectors are recommended.
We always have a window cracked in the berthing area when sleeping. Even when the outside temps are approaching 0.


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[jonplayers]

I am using this insulation in my rebuild. EnergyShield Wall Insulation - Insulated Sheathing | Atlas Roofing
Except the stuff I am using is foil on both sides.

I am using a flexible spray foam for the seams along the ribs.

I am going to add a foam sill gasket to the ribs for a thermal break after it is sealed up.

I am at this stage in my rebuild right now.
You can follow my progress here.

http://www.airforums.com/forums/f417...-94006-17.html

[TheCabin]

Has anyone ever performed or know of a thermal analysis (i.e. ASHRA type model) of an Airstream?

[perryg114]

The model would not be very good. The ribs conduct a lot of heat. Thermal breaks between the skin and ribs would help. The bedroom at the back of my trailer has cloth pads around it for a reason. These things are assumed as transient usage.


Perry

[Protagonist]

Originally Posted by perryg114

The model would not be very good. The ribs conduct a lot of heat. Thermal breaks between the skin and ribs would help. The bedroom at the back of my trailer has cloth pads around it for a reason. These things are assumed as transient usage.

The windows conduct a lot of heat as well.

[BTUs4You]

I'm in the polyurethane spray foam business and have both low and medium density foams at my disposal. I guess I can be thankful that our AS is not in need of a deep retrofit, so I haven't analyzed the expense and physics of a change of insulation, but it's important to regard the insulation and all other materials used in the AS as a system where changing any single component will affect performance of other components. It's possible to have unintended consequences when making "improvements" to the skin of the AS. Again, I haven't worked through a comprehensive hygro-thermal analysis though it's pretty easy to see the massive thermal bridging inherent in the aluminum skin design and construction and realize that improving thermal performance in only the insulated area will be minor in terms of energy conservation.

The real issue in Air Streams and all similar structures is moisture management. Of course bulk water intrusions must be controlled and so must water vapor. Water vapor moves by diffusion and is carried in air currents, and when warm, moist air contacts a surface below its dew point, condensation occurs. The condensed water can accumulate and contribute to corrosion, mildew, and rot of organic materials like wood.

Suffice it to say, the best thing you can do for the health of your AS is to keep it dry. Ventilate when showering and cooking. Dehumidify to 50% RH or less, and keep your baby inside or under cover when possible. Treat it like an airplane, which of course was the inspiration for AS.

Reducing humidity will go a long way to controlling condensation, especially in the South. In the north, it's very helpful to keep the interior surfaces warmer than dew point in order to control liquid water accumulation. This means heat of course. If you're not using your AS, it's a very good idea to leave cabinet and closet doors open so warm air can contact and conduct through as much of the skin of the AS as possible.

Sorry for the diatribe. Heat and moisture flow analysis is a complex science only recently getting much needed attention in the architecture, engineering and construction community, and while there's a lot we can learn from modeling and calculations, there's even more we can gain by simply applying common sense. Keep it warm and dry and please don't obsess over so-called "green" materials. If your beloved AS corrodes and must be scrapped ten years sooner than it should because you used inappropriate materials for thermal and moisture control, how "green" is that?

I just had a thought as I'm wrapping this up. I guess we should treat our Air Streams like our kids and grandkids, keep them warm and dry, right? My two-month old grandson is fussing, and I'll bet he could use a dry diaper ;-)


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[J. Morgan]

Regarding the thermal bridging of Airstreams, I put 1/4" plywood over the interior walls and it makes a significant difference in thermal efficiency when I compare it to my 78.

I wish I had gone ahead and put the foam insulation between the interior walls and the plywood but I didn't.

Dang it!!


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

[youngpeck]

Originally Posted by J. Morgan

Regarding the thermal bridging of Airstreams, I put 1/4" plywood over the interior walls and it makes a significant difference in thermal efficiency when I compare it to my 78.

I wish I had gone ahead and put the foam insulation between the interior walls and the plywood but I didn't.

Dang it!!


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

Please elaborate on "the foam insulation" you would use. How thick? What kind? Under all the plywood?

I'll be cladding the interior alum. skin on ours with 1/8-inch birch. Would appreciate your thoughts.

[J. Morgan]

I was considering some 1/8" stuff I saw on the shelf at Lowe's or Home Depot...

And I should have done it, but I got in a dang big hurry....


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

[youngpeck]

Originally Posted by J. Morgan

I was considering some 1/8" stuff I saw on the shelf at Lowe's or Home Depot...

And I should have done it, but I got in a dang big hurry....


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

Well, from the pictures I have seen of your trailer, the 1/4" worked just fine, and looks great! I'm getting Baltic Birch through a local hardwood supplier, about $25.00 a sheet (4x8). It's light, takes a nice oil finish, and bends very nicely. But what about the foam between the plywood and the aluminum walls? I'm curious to know about this. It must be something very thin. . . .

[Protagonist]

Originally Posted by youngpeck

But what about the foam between the plywood and the aluminum walls? I'm curious to know about this. It must be something very thin. . . .

Maybe this… Polyethylene - Closed-cell foam: insulation, packaging, foam toysQuarter-inch thick, made of the same stuff that forms the core of Prodex sheets, just without the aluminum foil facings.

[youngpeck]

That brings up the question of just what a thin layer of foam between the aluminum wall and the plywood would actually achieve. An additional thermal and/or sound barrier? The plywood itself would have the same qualities. I've never thought of foam in the middle of the sandwich, but it might be a good idea. One reason for attaching the 1/8" plywood is that I won't have to spend so much time cleaning the surface of the interior skins when I put them back on. The foam would also cushion the interface between the bumps of the alum. skin rivets and the plywood, too.

I see that the Foam Factory also has this and in 1/8" sheets:
Foam Insulation, Padding, Closed-Cell Foam - Polyethylene Roll

I like the idea of the thinner foam. Seems like it would be easier to use in between.