I think the ribs are a good place to interupt the flow of heat (or cold) into or out of the trailer. Aluminum readily transmits heat (or cold) and years ago the aluminum window industry started adding a thermal break between the inside and the outside of the window frame, greatly improving the thermal efficiency of the windows. In most cases, this thermal break was a plastic connector which continuously connected the inside aluminum extrusions to the outside aluminum extrusions. It worked great.
Since there is no way to do the same to the ribs on our trailers, the next best thing is to add a thermal break between the inside skin and the ribs. I think the best product for this would be strips of EVA foam. EVA foam comes in many thicknesses, densities, and toughnesses. Most people know it as the colored foam used in most cheap flip-flop sandals. It is available from this supplier: Ethylene Vinyl Acetate - Canal Rubber Supply Company - Sitemap
If I ever need to remove the inner skin of my trailer, I plan to add strips of 2mm thick EVA foam to the inside rib faces before reinstalling the skin panels. The plan is to use double stick "Super Seamstick Tape" (see Seamstick 1" Super Seam BastingTape by 3M (60 Yds) ) to apply strips of EVA foam which are a little wider than the rib face then connect the inner panels to the ribs with rivets like the factory.
The weight is negligable and it could reduce the heating (or cooling) load by as much as 20% (my own guesstimate(unscientific))
Here's a pic of a thermal break used in an aluminum window frame.
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2002 Toyota Tundra Not that Bob Thompson, the other Bob Thompson!
Last edited by Bob Thompson; 07-04-2009 at 09:38 AM.
Reason: add pic
The EVA foam is interesting. What's the upper limit on thickness that could be applied to the ribs? Aspen Aerogels makes a material that's designed to cover house framing, but it's 5mm thick. It's interesting because it's light, flexible, and it's over R-10 per inch. I'm new to all this and I'm enjoying learning more . . .
Thickness is not near as important as having any separation of the interior skin from the rib, hence my choice of 2mm thick material. Heat or cold travels thru aluminum really easy. Even 2mm will work fine to seriously restrict that flow.
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2002 Toyota Tundra Not that Bob Thompson, the other Bob Thompson!
I just got done remodeling my 32' Excella. I removed the walls and insulation half way up (my floor was rotten and I had to tear it out; thus, the 1/2 walls). When I put it back, I used 1 1/2 pink Styrofoam board and used spray foam insulation to seal up all the cracks and gaps. Worked pretty well. I tried using the spray only and it just was not practical. Work much better to use it to fill in the gaps in the floor and walls.
I strongly concur with rangebowdrie, above. After lots of research, I intend to fully insulate my 72 Overlander with TigerFoam, a closed-cell foam. Many of the posts refer to just "foam". That's like just referring to "aluminum". I think anyone would agree there is a vast world of difference between 2024-T3 alloy and 3003-0. Same with foams. Do not use an open cell foam. Just yesterday a RV dealer told me he had used closed cell foam many times and never had it 'turned to powder' or 'absorbed water'. If you want something that will absorb and hold water, just try fiberglass insulation. My Overlander had serious black mold that started from a moist area in the rear. Never again will I tolerate fiberglass as an insulation. Maybe some of the forum members should take a look at the current world and not keep repeating urban legends.
I find this tread very informative. I recently purchased a 1950 Liner and am in the process of restoring her. I just finished the shell off floor replacement and will now be moving to the inside to replace all the interior skins except the end caps. Insulation do's and don'ts is what lead me to this thread. I too was going to opt for the spray foam insulation. I've used it in a marine application with great success. If you read the specs on TigerFoam is says its non-wicking, moisture resistant, seals against water etc. Sounds like a great product for an Airstream renovation project.
But I feel I'm missing something or maybe I don't understand the physics of insulating, venting and moisture. What is the proper way in insulate a unit. Does there need to be an air space for the moisture to vent? Should the insulation be firmly against the outer or inner skin? Should the space between the panels be completely filled with insulation? Vapor barrier? What's a proper installation of insulation in an Airstream? My original insulation in the shell and floor was fiberglass. The skin was completely filled with insulation and it would appear the interior skin has never been removed before now and the product appears in tact. There is no evidence of mold or moisture damage and this is a 59 year old unit.
We insulate with Polyisocyanurate foam panels to achieve about R-12 in our projects. The panels are faced with aluminum which allows us to use aluminum tape to form a sealed vapor barrier and keep the moisture away from the skin.Brett Hall
Timeless Travel Trailers
Thanks Brett. I found 1" Polyisocyanurate foam panels at Lowes with aluminum facing on one side. Is that what you used, or should there be aluminum on both sides? If there's aluminum on one side only should it face in or out, or does that depend on whether you're more interested in keeping the trailer warm or cool?
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Grant Davidson
Milton, ON
1964 Overlander
1974 Sovereign
2005 F-350 SRW 4x4 crew cab long box
1965 Avion C-10 Truck Camper
Someone mentioned that making sure the area was completely sealed due to the fact that the aluminum will transfer heat. So the foil skin sounds great. Just make sure that the gaps are sealed. I just started camping with my AS after the restore with my kids. I love it. Still working out the kinks and learning a little, like raise your pads before you hook up your tow vehicle. I just crushed me back pad because I didn't raise it before I ran my electric tongue raiser. $50 mistake and maintenance. Oops.
Best wishes.
I gave up trying to promote foam insulation of today. Four years ago I had all my shops and barns done with this method. My home is built with SIPs ...6 inches of foam roof and 4 inch walls. No out gassing, no formaldahyde, no fire hazzard, etc., etc. I was convinced not to use foam in the Airstreams....but I will always wonder....what if?
Foam technology is evolving quickly. Some contractors keep up with this stuff, many don't and continue to use the pink stuff. Methods to eliminate or reduce the effect of thermal breaks are also evolving. Thermal breaks are areas where cold or heat is quickly transmitted between the inside and outside. Metal is excellent at transmitting cold or heat, but pads between the ribs and the interior and exterior panels could help make a difference. Airstream sticks with old methods for years and years. They did try thermopane windows some years ago and it was a disaster—that technology has advanced also, but I suspect someone at the factory uses the old excuse, "we tried that".
Grant, I'd do a search. I know technology is changing. I read Fine Homebuilding and they have articles on this from time to time, though a trailer is different from a house.
Arctic Fox makes 4 season trailers—check their website for ideas too.
You may have to improvise based on what you learn about houses.
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