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Old 09-18-2006, 12:20 AM   #15
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Expanded Polystyrene Board

Needed >48" wide aluminum for my belly pan, found it at Fruehauf Trailers in San Antonio. Chatting with counter man, I asked what they use as insulation under subfloor of their refrigerator trailers.

Answer: expanded polystyrene board, cut for tight fit with handsaw, no glue or fasteners needed. Then he told me where to buy it.

For ~$20 a 4'x8' sheet, I got 3" thickness, with R-value nearly 12.

It really does cut like butter with a fine-toothed sawzall. Had to measure carefully and trim a few edges after original cuts, but when you get it right, it squeaks up in there and stays put! SO much easier than any of the other options I've read about!

I really don't think a big outfit like Fruehauf would use it if "crumbling" due to road vibration were a problem -- their trailers cover thousands of miles a month -- but time will tell.

Here's a pic I took halfway through installation.
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Old 09-18-2006, 06:21 AM   #16
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The correct way in my opinion is NO INSULATION in the belly.

This guy is 100% on target http://www.airforums.com/forum...47-post14.html

After dropping my belly pan up front where there was no apparent leak the 2" fiberglass was a wet balled up sponge that was a moisture source to rust the frame, I took it all out and hosed the whole area. The hose knocked out a lot of what was left on top of the frame too.

I'm putting the foil R-14 on top of the floor, then pergo.

Pergo tells you to put a foam layer down so the Foil will take it's place.
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Old 09-18-2006, 08:39 AM   #17
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Quote:
Originally Posted by Lipets
The correct way in my opinion is NO INSULATION in the belly.

This guy is 100% on target http://www.airforums.com/forum...47-post14.html
Getting deeply into this subject comes close to the medieval argument over how many angels can dance on the head of a pin. I'll bet dollars to donuts that one could not sit inside an unknown trailer and tell whether or not there was insulation under the floor. This is due to the whole 'heat rises' phenomenon and is the same reason our homes have minimal insulation in the floor.

Two situations at the extreme of Airstream use might provide a small margin of value for floor insulation. Neither would seem to impact energy consumption to a significant degree.
1. Wintering -- pipes are down at floor level. Furnace forced air is going to do more to keep them from freezing. You'd have to run the furnace anyway trying to maintain in freezing weather -- not because of a little or a lot of R-value under the floor. Heat loss through the shell (metal ribs & only 2" of fiberglass) and windows would greatly surpass what is being lost through the floor. Would floor insulation help you stay out at 14 degrees instead of 15 degrees without? I dunno -- it's dancing too close to the edge for my comfort.
2. Driving across summer hot pavement at midday has been mentioned. You probably could measure a small increment of interior heat gain due to radiation from the road. But you'd really like to have a 30A plugin waiting to run the A/C when you pull off the road. And heat gain through the shell and windows would again greatly surpass that through the floor. There's more than one reason we find peace gazing at a sunset.
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Old 09-18-2006, 09:46 AM   #18
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Quote:
Originally Posted by Canoe stream
Getting deeply into this subject comes close to the medieval argument over how many angels can dance on the head of a pin.
yep. quite possibly, it ain't worth the hassle. I'm thinking the philosophy of insulating the floor may just be a "every little bit helps" one, rather than "$ saving in fuel consumption". the small heating and cooling systems in our trailers can barely keep up with their assigned tasks, even if "fuel is no object".
I
Quote:
Originally Posted by Canoe stream
'll bet dollars to donuts that one could not sit inside an unknown trailer and tell whether or not there was insulation under the floor. This is due to the whole 'heat rises' phenomenon and is the same reason our homes have minimal insulation in the floor.
I may be wrong, here, but I don't think that "heat" rises; hot air rises. My 12-year-old (built to current codes) house has lots of insulation in the floor. My understanding is that the warm floors in the living space will radiate heat into the cold basement, and thats what the fiberglass is hampering. "sound dampening" is another thing that is seldom mentioned in these threads. again, I don't think its a really big deal, but if you're a really light sleeper...

Quote:
Originally Posted by Lipets
The correct way in my opinion is NO INSULATION in the belly.
well, thats one conclusion you can draw. Another way might be "no insulation that has a sponge-like quality up against materials that are prone to moisture damage without using a vapor barrier". It doesn't seem to be a big problem in the walls...they're alluminum. But steel or wood...thats a problem. I don't think its just "condensation"; sure, there'll be more when the trailer is occupied, but there won't every be "0". The problem is the condensation trapped in a sponge, and held against the steel framework. Of course, it doesn't seem to me that it would be practical to install a vapor barrier under the floor unless you're the factory, or you're doing a full shell-off.
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Old 12-20-2013, 02:06 AM   #19
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Floor insulation

Any way to blow the 'fluffy roll-type' fiberglass between the belly pan and sub-floor?

I put 5/8'' double aluminum sided polystyrene sheets over the yellow pine plyboard and then 3/4'm shiplap redwood floor on top of the insulation.

This adds good value of insulation. I packed all the seems with mohair and built insulated boxes over the wheel wells.

I would like to add additional insulation in the belly pan to help.

Anybody know of a way to blow the bellypan space with the fluffy fiberglass insulation?

Em
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Old 12-20-2013, 02:15 AM   #20
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I live comfortably in -30 degree weather. Alpaca felt over the windows help most. Rugs help too.
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Old 12-20-2013, 09:04 AM   #21
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Not a good idea. The belly pan area is not waterproof and any moisture will wick up to the frame areas and cause serious frame corrosion. The blown in will also get waterlogged and matted to the lower aluminum skin also causing corrosion. Mice also love the nesting properties of the insulation. Your best bet is to drop the belly pan and use rigid foam sheet.


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Old 12-20-2013, 11:43 AM   #22
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After having dealt/dealing with rusted frames on the Airstreams, caused by sopping wet fiberglass insulation, I am convinced that soft insulation IS NOT the way to go. On my current rehab the game plan is to go back with some form of rigid insulation, whether I use Expanded or the more dense Dow Board has yet to be determined. I also have good access to polyiso but I don't think it will have the longevity of the EPS or the XPS.

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Old 12-20-2013, 11:50 AM   #23
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Quote:
Originally Posted by wahoonc View Post
After having dealt/dealing with rusted frames on the Airstreams, caused by sopping wet fiberglass insulation, I am convinced that soft insulation IS NOT the way to go. On my current rehab the game plan is to go back with some form of rigid insulation, whether I use Expanded or the more dense Dow Board has yet to be determined. I also have good access to polyiso but I don't think it will have the longevity of the EPS or the XPS.

Aaron
Also polyiso can absorb water and is not a good insulation to be used where it could become wet. It has a good R value per inch but only if kept completely dry.
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Old 12-20-2013, 02:05 PM   #24
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This is what I used for the walls and below the floor. It won't turn to powder and it won't absorb enough water to matter. You don't want any type of fiberglass mat or loose insulation. It will absorb water and hold it against the frame and floor. If you live in a moderate climate, I would suggest you don't use anything in the floor. I insulated the sections between the frame and the outside walls only because it would be a pain to access that area again. Right now I have no insulation between the frame rails but my belly pan screws on so I can get under there and add insulation if I ever need to. I used 2 layers of .5" RMAX in the walls sealed with aluminized duct tape. You can add some of the radiation barrier as the last layer if you like.


http://www.rmax.com/downloads/DataSheets/rmp3.pdf

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Old 12-20-2013, 05:46 PM   #25
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One word of caution, poly-iso is flammable and will support a rapid flame spread particularily when combustion air is inducing a 'chimney effect' as would typically be present beneath a trailer with its various penetrations, large or small.

This is why the airline industry prohibits its use.
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Old 12-20-2013, 08:29 PM   #26
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It does have aluminum on both sides which will limit the flammability. Plastics in general, are pretty toxic when burned. They also make rigid fiberglass boards that are commonly used for HVAC ducts.

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Old 12-21-2013, 05:41 AM   #27
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Belly pan air space

Seems that the belly pan space is a good dead air space for insulative value. I'll be satisfied by that.
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Old 12-21-2013, 01:26 PM   #28
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A wild idea...

I just had a wild idea. How about using Styrofoam shipping pellets - or maybe even bean bag pellets? If you have access from the top you could perhaps just pour the pellets in - maybe adding plastic film first. Otherwise maybe the thing to do would be to fill up plastic bags and lay them in place - either from above or from below. If from below it might be possible to just add netting or even lace string from frame member to frame member to hold the bags in place until the belly pan is put back in place. Sure it might not be as good as solid foam bats but it might be good enough and it might be easier to get it to fit in odd shaped spaces.
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