Insulation between floor and belly pan. What to use?

[68Glbtrotter]

I've not seen too much discussion about types of insulation that can be used between the floor and belly pan of old trailers, like '68 Globetrotters. Any hints on material and installation?

Thanks,
Dan

[Moonshot]

Dan,

I seem to recall a thread months ago where several people were advocating the spray on insulation. This is the canned stuff that rapidly expands and you saw off the excess with a serrated blade. You can buy it at Lowes or Home Depot. I used some last week to seal some cracks around the exterior of my house. On the plus side if it gets wet it seems like it wouldn't be harmed and on the minus side if you have to get to your pipes later you'd need to chisel the stuff out of the way.

I can't find that thread in a search. Maybe someone else will chime in with their thoughts.

Scott

[overlander63]

I remember that most people advocate the use of the roll-type fiberglass insulation, as it won't turn into powder from the movement of the trailer while driving.

[CanoeStream]

Ditto on overlander63's comments. During manufacture a wide unbacked fiberglass batt was laid over the frame before the plywood floor was installed. So you will note that the original fiberglass is pinched at any frame locations. I used stainless steel staples to reattach standard 16" fiberglass to the floors between outriggers when I had the banana wrap off my Argosy.

Experience in other threads has been that foam insulations turn to dust during towing movements. There really isn't any reason to get expensive with floor insulation for the same reason we put more insulation in our attics than our floors at home. The shell around you has much more influence on internal heating and cooling loads -- it has no thermal break and a scant 2" of fiberglass. The floor doesn't really pass much heat in or out.

One potential problem with spray-in foam would be loss of ventilation under the floor. This ventilation is important to retard moisture problems with wood, steel, etc. That is the very good reason your banana wrap & belly skin is loose fitted.

[malconium]

I am a fan of reflective foil insulation. I would suggest installing some of that to the bottom side of your floor. It would be best if you could install it at least 1/2" below the floor so that there is an air gap between the wood and the top of the foil. This can easily be done by using narrow strips of plywood or foam insulation board around the edges of each cavity. You can then either glue or staple the foil to the strips. I bought my foil from Lowes and the brand name is Reflectix. Check out the following thread for a lot of information ab out foil insulation:

http://www.airforums.com/forum...ods-14803.html

Malcolm

[Over59]

Going down the road in summer with the surface 100+++ degrees I suspect you get significant heating from the road. If you have the belly pan off consider foam sheets. I used 2". The complete set up is, painted the underside of the floor with nanoreflective paint, then under that double sided reflective 3/8 bubble wrap with random bubbles, airspace, foam board cut to fit very snug. Filled the ends with foam above the foam board.

[ArtStream]

I was just at the factory and can report that they are now using the reflective bubble type in place of fiberglass.

Michael

[Chuck]

Originally Posted by artlink

I was just at the factory and can report that they are now using the reflective bubble type in place of fiberglass.

Michael

Interesting. Is it just in the floor, or the walls, too? how is it attached? (air gap?) is it in conjuntion w/ solid foam or any other material?

[1959newbie]

Originally Posted by artlink

I was just at the factory and can report that they are now using the reflective bubble type in place of fiberglass.

Michael

Michael, are you out there somewhere? I also am interested in how the factory is using foil bubble-type insulation now.

[LI Pets]

This stuff looks good http://www.insulation4less.com/highr_FfmF.asp

• Is waterproof and non-absorbent.
• Provides Class A/Class 1 fire rated protection.
• Provides 19 DB Soundproofing.
• Convenient flange tabs on sides.
• Does not mildew or promote fungus growth.
• Does not provide nesting for birds, rodents or insects.
• Is safe for workers to use as there are no fibers to breath or cause skin irritation.
• Has more insulation value than 6 inches of common mass insulation products.
• Can be stapled, nailed, glued or sewn.
• Easy to cut
• Reflects 97% Radiant Heat
• R-14.5

$70 for a 4x25 piece.

[malconium]

Bob,

This does look like a pretty nice product. I do see, though, that they also sell foil-bubble-foil. The R-value is almost the same but the price is less for the bubble type. These guys provide free shipping to most of the 48 states too so that would be a good thing. I just looked up foil insulation at the Lowes website and their foil-bubble-foil looks to be cheaper for the 4'x25' roll at $48.67. This is about $0.49 per square foot. The larger foil-bubble-foil roll at the site you quoted is a much better deal though at about $0.27 per square foot. With free shipping that would be a good savings. Whether or not the larger roll will work for you depend on how much you need though. The floor area of my 31' unit is right around 200 square foot.

http://www.lowes.com/lowes/lkn?actio...l%20insulation

In my installation in the walls I don't actually use any staples so puncturing the bubbles is not really a problem. If you were going to install it under the floor then staples might be a good way to go. It would actually be better not to staple directly to the bottom of the floor though since this would not leave an air gap above the foil. From what I understand reflective foil insulation works best if there is an air gap on both sides of the foil. The side that is in direct contact with something will have a less effective reflective barrier. I think that this means that foil that is stapled to the bottom of the floor would be better at keeping heat out than it would be at keeping heat in.

There is a lot more information about foil insulation in the following thread. The specs for the type of foil available at Lowes and Home depot are available there.

http://www.airforums.com/forum...+insulation%22

Malcolm

[Wabbiteer]

From above link -

http://www.insulation4less.com/highr_FfmF.asp

A longer roll length (7 X) reduces price to $34 for 4x25 roll, with $237 total price (500sq ft) that includes shipping... so it is VERY competitive price as compared to reflectix type wrap from Home-depot, etc.. (reflectix $37.95 x 7 = $265.65 plus tax $284.25)

I have my twenty-seven foot Airstream belly 60% off and am pondering using the foam core type - for rigid foam board to meet the R-14 value I'm looking at .80¢ sq ft vs. .47¢ sq ft for the PRODEX Foil-Foam-Foil type...

Anyone care to check my math? The Prodex R-14.5 figure adds about R-2.5 value over the reflectix in best-case testing comparison..

Thank you Lipets, good timely link!!!

[Wabbiteer]

eek! Typo found after edit window expired - bulk roll purchase is 4'x175' so 700 sq foot coverage... I am ordering this tonight...

[2airishuman]

Originally Posted by 68Glbtrotter

I've not seen too much discussion about types of insulation that can be used between the floor and belly pan of old trailers, like '68 Globetrotters. Any hints on material and installation?Thanks,Dan

hi dan

a review of several of the body off restoration threads will reveal how each fixeruper has done the floor insulation.
i've read bubble foil, fiberglass and a few foam... blown or sheet.

currently the factory is using bubble foil in the floors as artlink reports...

here is link to a photo as proof...post 14.

http://www.airforums.com/forum...ble+foil+photo


there are issues regarding ventilation and fixing it to the walls but the restortion threads usually cover these things

i've also looked at some professional rehabs...some fiberglass, some foil...only occasionally blown foam...

cheers
2air'

[1959newbie]

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.

[LI Pets]

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.

[CanoeStream]

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.

[Chuck]

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

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...

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.

[Ejmille]

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

[Ejmille]

I live comfortably in -30 degree weather. Alpaca felt over the windows help most. Rugs help too.