Insulation- Prodex or Foam Insulation Board?

[Danny Z]

Hello, I am new to this site and one of the challenges I am having is that there is so much information! I spend hours reading threads and start to come to a conclusion about what I am going to do and then someone comes along and suggests something else and I end up starting all over on a new series of threads I didn't know existed. I would love a general consensus (good luck with this request, right ) on insulation:

Prodex style insulation or a Rigid foam insulation board like Rmax from home depot?

And if the rigid board, what thickness?
And does it need an air gap like a prodex style does?
Thanks so much for your help!

[Protagonist]

If you want the maximum R-value per inch of thickness, nothing beats rigid polyurethane foam panels, with an R-value of 7 to 8 per inch depending on brand.

However, since you're insulating curved walls, you might do better with a Prodex-style flexible insulation. But don't get Prodex brand! The core material of Prodex is polyethylene foam, which is then backed by aluminum foil on both sides. Thing is, you don't need aluminum foil inside an aluminum-skinned Airstream. So just get Polyethylene foam insulation, without the foil. You can get it thicker, up to about 2" thick (the maximum thickness of Prodex is only 10mm) and cheaper by getting the foam without the foil. R-value is about 3 per inch though it varies somewhat with density. You can easily curve it to fit your walls, and easily trim it to fill the void spaces.

Polyethylene foam comes in different densities, so when you buy it you need to specify both a thickness and density. Lower density is a better insulator because it has more entrained air, 1.2 pounds per cubic foot is a good value to shoot for. That means for a 2-inch thick layer, the weight will only be 0.2 pounds per square foot of insulated surface, so it won't add a lot of weight to the trailer, either.

[KrisE MN]

Originally Posted by Protagonist

If you want the maximum R-value per inch of thickness, nothing beats rigid polyurethane foam panels, with an R-value of 7 to 8 per inch depending on brand.

However, since you're insulating curved walls, you might do better with a Prodex-style flexible insulation. But don't get Prodex brand! The core material of Prodex is polyethylene foam, which is then backed by aluminum foil on both sides. Thing is, you don't need aluminum foil inside an aluminum-skinned Airstream. So just get Polyethylene foam insulation, without the foil. You can get it thicker, up to about 2" thick (the maximum thickness of Prodex is only 10mm) and cheaper by getting the foam without the foil. R-value is about 3 per inch though it varies somewhat with density. You can easily curve it to fit your walls, and easily trim it to fill the void spaces.

Polyethylene foam comes in different densities, so when you buy it you need to specify both a thickness and density. Lower density is a better insulator because it has more entrained air, 1.2 pounds per cubic foot is a good value to shoot for. That means for a 2-inch thick layer, the weight will only be 0.2 pounds per square foot of insulated surface, so it won't add a lot of weight to the trailer, either.

I found this on the Prodex site and it makes sense to me.
Prodex eliminates the moisture (condensation) from forming on the metal sheeting. It does it by making the temperature of the metal sheeting on the building approximately the same on the inside as the outside. When the heat or cold from outside comes through the metal skin it hits the outside aluminum facing of Prodex and is reflected back upwards through the underside of the metal sheeting. This process keeps the metal sheeting temperature consistent on both sides. In addition, the inside layer of aluminum in Prodex reflects away the heat (heater) or cold (air-conditioning) from inside the building, from getting to the metal skin. This also helps in preventing condensation.

Hot Metal Walls - Radiant Heat Transfer

Ever wonder why the walls inside of a metal building are so hot in the summer and so cold in winter? The metal skin magnifies the heat of the summer and frigid temperatures of the winter. Metal is a very good conductor of heat and cold. In hot weather, metal framing and sheeting rapidly transfers the sun's heat into a building, and in cold weather it rapidly transfers the heat out of your building.

Prodex reflects 97% of the radiant energy (primary source of heat flow) that strikes it - Which also protects your animals from Black Globe Effect. Prodex also reflects back the heat inside your steel building. Each unit of radiant heat energy that is reflected away from your barn in the summer, and each unit that is reflected back during the winter, means less operation of your heating and air conditioning system - Less wear and tear on your equipment - Less money you pay in utility costs.

[aholmquist]

I am reading everywhere that Prodex is a huge scam. Their claims of a high R-factor are totally bogus. So this guy (video posted below) is recommending using the foil over insulation to help with that heat barrier. Of course he is referring to an attic and not putting insulation right up next to it so my question is does anyone have any feedback on using an attic foil radiant barrier in the walls of the AS? Will it lose its effectiveness if you put the inner skin right back on top of it? And what insulation would go best under that? I am doing research on it so I might be back to add more to this post. I am set to do insulation by early next week so I am trying to figure this out fast and I want the higheest R-factor possible because I live up north in Montana and would like to spend some part of the year here is possible.

https://www.youtube.com/watch?v=Vl8GslJ9hnI

[Unka Jack]

There is an older thread "Insulation effectiveness test" that showed hard data from actual experiments about the different types of insulation. That deals with just this topic. I'm just having a hard time copying and pasting the link.

[Thomas31]

I completed a full remodel and used "Polar Fold", very good R value and best of all it bends both ways so you can use it in the radius ends, it also added some rigidity to the walls for the inside skin between the ribs. Comes in 1/2" sheets and we used three sheets to fill the walls, easy to cut to fit snug around ribs, lights, etc.

[batman]

I agree that Prodex is probably exaggerating there R-value rating.

The walls flex so much when traveling I did bot want to use a rigid foam product. Additionally having to cut the hard foam panels were wiring passes through each section between the ribs.

My solution for the walls was to sandwich Johns Manville (formaldehyde free) fiberglass insulation between 2 layers of Prodex and foil taped all seams. Under the floor I used 2" of rigid foil backed foam glued to the underside of the sub-floor then secured that with screws and fender washers.

Know matter what insulation we use in the walls, we are going to have both Heat and Cold transferred to the inside of the coach by the naked ribs that are riveted directly to the outside skin and the inside skin.
Window treatments are an added benefit as well for our single pane windows, if it is extreme weather I have cut piece's of Prodex for the inside of my windows. I put them in when it is in storage as well.

Prodex, over rated, probably. Is it still useful, I think so.
Best of luck with your referb.

-Dennis

[Unka Jack]

Here's the link I was referring too:
http://www.airforums.com/forums/f46/...sts-40442.html