Insulating a Burro - Fiberglass RV


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Old 12-28-2010, 12:49 PM   #1
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Insulating a Burro

I am restoring a 1980 Burro 13, although restoration has slowed down due to the cold weather. The cold has me thinking about adding insulation between the inner and outer shell. I am not a fan of Reflectix and was thinking of adding flexible closed cell foam insulation like polyethelene. It would be easy enough to glue 1/2" sheets of flexible foam to the outside walls below the cabinet level. Getting the insulation sheets between the shells up higher without leaving gaps would be more difficult. I am replacing all the windows so that may help with access.

I was also thinking of using "foam in place" insulation (like Great Stuff) between the shells, but I am not sure how I could tell if I got full coverage, or if there were gaps. The expanding foam might distort the shells, although there is foam available that expands less and is used around house windows and doors to avoid distortion.

The body is currently off the frame as part of a floor replacement and I was thinking of adding an insulating foam sheet between the floor and frame before putting the body back on the frame. Depending on the type of foam, I may add a plywood panel beneath the foam to protect it from road debris.

Has anyone used expanding foam in a double wall egg?

Anyone installed sheets of insulation between the double walls? If so how did you slide it up to the top, some places have a very tight fit.

Anyone add floor insulation between the frame and floor?

Thanks for any advice and insights.

Andy
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Old 12-28-2010, 03:49 PM   #2
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I know this topic has come up before, so you want want to try a quick search for insulation/Burro/UHaul/double wall, etc. Some folks have tried the Great Stuff, but caution about the expansion and distortion. I think the toughest places are in the upper walls, since the two shells pinch together a bit. The best time to do all of this is when you have the shell as exposed as possible, with cabinets removed or at least opened up. Good luck!

(We have a similar construction in our UHaul VT, but find the air gap insulation good enough for our minor cold weather camping.)
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Old 12-28-2010, 08:03 PM   #3
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I know this topic has come up before, so you want want to try a quick search for insulation/Burro/UHaul/double wall, etc.
Thanks Kevin, I had already searched and that is why I posted, to see if there was any additional experience.

In my search I did not find anything about anyone insulating between the floor and frame.

I saw some cautions that expanding foam could cause deformation of the shell but did not find any good or bad experience from people that had actually tried it.

Found some posts about sliding insulation between the shells, but no mention of how much coverage that they were able to get.

Thanks for the reply, Andy
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Old 12-30-2010, 01:44 PM   #4
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Originally Posted by Andy B

Thanks Kevin, I had already searched and that is why I posted, to see if there was any additional experience.

In my search I did not find anything about anyone insulating between the floor and frame.

I saw some cautions that expanding foam could cause deformation of the shell but did not find any good or bad experience from people that had actually tried it.

Found some posts about sliding insulation between the shells, but no mention of how much coverage that they were able to get.

Thanks for the reply, Andy
I have heard folks caution against using expanding spray foam for another reason: over time road vibration causes the foam to break down into dust. Trapped between walls, with no where to go, perhaps this isn't a big deal, but no doubt your insulation values will be lost.
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Old 12-30-2010, 09:49 PM   #5
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I have heard folks caution against using expanding spray foam for another reason: over time road vibration causes the foam to break down into dust. Trapped between walls, with no where to go, perhaps this isn't a big deal, but no doubt your insulation values will be lost.
Robert, thanks for the heads up about vibration, I will have look into that. The Great Stuff product description says "Seals and insulates vans and campers." So I expected that it would work in an egg, but maybe there are long term issues. There are also other types of foam in place materials, maybe some degrade and others do not.

Andy
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Old 12-31-2010, 12:12 AM   #6
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I did some searching and found a 10 page discussion about foam insulation deterioration to powder on an Airstream forum.

Spray Foam Insulation - Airstream Forums

After reading all 133 posts I came away with the following:

1) There are many different types of foam in place insulation.
2) Insulation foam technology has evolved and improved considerably over the years.
3) No mention was made of what type of foam turned to powder.
4) Some foams installed 20+ years ago look like new with no deterioration.
5) Some foam manufacturers when contacted say their foam will not powder.
6) This type of foam has some of the highest r-values available
7) The foam would bond the inner and outer shells together and increase strength considerably.

Andy
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Old 12-31-2010, 05:15 AM   #7
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I presume the Airstream discussion was about spray insulating the inner side of their single-skin trailers, like a house. So the question about the durability of the foam is relevant, but not the installation process.

Inject/pour-in-place foam has long been used in the boat industry but only when both mouldings are clamped in heavily-reinforced moulds - the forces that can be produced during the foaming process are huge.

I wouldn't be surprised if injecting just one or two seconds too much foam between a Burro's skins would not only deform the exposed panels, but also break some of the weaker joints - for example, popping the furniture off the now-distorted walls.

If I were going to do this (which I wouldn't...) I would build a little test rig - something like a 24"x24" sandwich of 1/8" ply inner and outer skins screwed to 1x1 framing around three sides - and then try out injecting foam in the gap. A broken test rig is soo much better than a broken trailer.
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Old 12-31-2010, 09:09 AM   #8
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I presume the Airstream discussion was about spray insulating the inner side of their single-skin trailers, like a house. So the question about the durability of the foam is relevant, but not the installation process.

Inject/pour-in-place foam has long been used in the boat industry but only when both mouldings are clamped in heavily-reinforced moulds - the forces that can be produced during the foaming process are huge.

I wouldn't be surprised if injecting just one or two seconds too much foam between a Burro's skins would not only deform the exposed panels, but also break some of the weaker joints - for example, popping the furniture off the now-distorted walls.

If I were going to do this (which I wouldn't...) I would build a little test rig - something like a 24"x24" sandwich of 1/8" ply inner and outer skins screwed to 1x1 framing around three sides - and then try out injecting foam in the gap. A broken test rig is soo much better than a broken trailer.
Andrew, the test rig is a good suggestion, but even with good test rig results with a uniform gap, the gap between the trailer shells varies in size considerably in different areas and would produce different results. My major concerns are not the powdering of the foam, as some types remain flexible, but rather how to effectively fill the gap between the shells without over filling. Most of the areas to be filled have no visual access and I can not think of a way to insure they get filled but not over filled. If someone has tried it, I would love to hear their experiences, good or bad.

There is a similar issue if sheets of flexible foam are inserted between the shells. Visual access is limited and there are compound curves involved. It would be difficult to insert sheets of foam without leaving large gaps between sheets and no way to fill those gaps. Getting sheets of insulation to some areas would be very difficult. It would be great to hear from anyone that has tried this and any methods used to get the insulation to some of the more difficult areas.

Thanks,
Andy
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Old 12-31-2010, 08:45 PM   #9
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I was in Orchard Supply today and they were selling bags of large bean bag pellets. Theirs are much bigger than the old tiny pellet size I'm familiar with. They're about 3/16" and about $12 for maybe 2 or 3 cubic feet. I wonder if you could seal the lower edge with expanding foam and then blow these things in through the roof fan access, or up from the bottom. They should find their own level and fill all the available space, and they wouldn't stop you from running wires or making panel repairs down the road. You could add more beans as they settle out, too. I think it might take a half dozen bags to fill the gaps, but it seems doable. You'd want to seal around the closet area I think, or you could have an avalanche of beans if you ever pull the closet out. What do you think?
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Old 12-31-2010, 09:13 PM   #10
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It is doubtful that anyone would pull the closet, or any other bit of furniture out of a Burro. It is molded and is part of the inside shell. Nothing is riveted on.. its basically all one piece. The only attachment points are on the floor, under a flange. They screw into the subfloor.

I thought Uhauls were the same? I haven't looked that close at any of them.

It could be done, I suppose, but it would take a lot of effort and skill, or a really big budget.

Andy, both my 13 and 17 foot Burros came with the factory insulation, so I had no need to find the way to do this, but I will tell you that I insulated where they didn't and it made a difference. This would be lining all the cubbies under the seats and back walls of the closet and kitchen cabinets with reflectix. Basically..anywhere it was only a single layer of glass. I know you don't like it, but it did work well. It was easy to do with a box knife and foil tape.

You may have to live with some gaps and just shove as much up into the walls as you can.. but some is better than none.
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Old 12-31-2010, 10:33 PM   #11
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Originally Posted by Matt in SV View Post
I was in Orchard Supply today and they were selling bags of large bean bag pellets. Theirs are much bigger than the old tiny pellet size I'm familiar with. They're about 3/16" and about $12 for maybe 2 or 3 cubic feet. I wonder if you could seal the lower edge with expanding foam and then blow these things in through the roof fan access, or up from the bottom. They should find their own level and fill all the available space, and they wouldn't stop you from running wires or making panel repairs down the road. You could add more beans as they settle out, too. I think it might take a half dozen bags to fill the gaps, but it seems doable. You'd want to seal around the closet area I think, or you could have an avalanche of beans if you ever pull the closet out. What do you think?
Matt, that is an interesting idea! I had not thought about blown in insulation at all. In some places the gap between the shells is small, so maybe the smaller pellet size would work better. I wonder if static electricity would be an issue trying to blow them in. I will have to think about it some more, maybe get some R-value information.

Thanks,
Andy
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Old 12-31-2010, 10:54 PM   #12
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Andy, both my 13 and 17 foot Burros came with the factory insulation, so I had no need to find the way to do this, but I will tell you that I insulated where they didn't and it made a difference. This would be lining all the cubbies under the seats and back walls of the closet and kitchen cabinets with reflectix. Basically..anywhere it was only a single layer of glass. I know you don't like it, but it did work well. It was easy to do with a box knife and foil tape.

You may have to live with some gaps and just shove as much up into the walls as you can.. but some is better than none.
Gina, Thanks for your Burro insulating experience. I am planning on using closed cell foam sheets on the outside walls behind the cabinets, etc. like you did with the Reflectix. Closed cell foam sheets should be easy to work with like Reflectix, it is good to hear that it makes a difference. When I remove the windows next spring I will find out if that gives me access to cavities at a higher level. Does anyone know if the Burro inner and outer shells are bonded together at the window openings? If the shells will come apart a bit with the windows out, I could slide some insulation into the cavities through the edges of the window openings.
Thanks,
Andy
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Old 12-31-2010, 11:05 PM   #13
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Matt, that is an interesting idea! I had not thought about blown in insulation at all. In some places the gap between the shells is small, so maybe the smaller pellet size would work better. I wonder if static electricity would be an issue trying to blow them in. I will have to think about it some more, maybe get some R-value information.

Thanks,
Andy
I found this:

Quote:
The thermal resistance or R-value of polystyrene foam board depends on its density. They typically range from R-3.8 to R-5.0 per inch. Polystyrene loose-fill or bead insulation typically has a relatively lower R-value (around R-2.3 per inch) compared to the foam board.
Energy Savers: Polystyrene Insulation Materials.

I think the big benefit will be cutting convection currents in the wall. I am pretty sure mine's a draft magnet!
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Old 12-31-2010, 11:13 PM   #14
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Originally Posted by Gina D. View Post
It is doubtful that anyone would pull the closet, or any other bit of furniture out of a Burro. It is molded and is part of the inside shell. Nothing is riveted on.. its basically all one piece. The only attachment points are on the floor, under a flange. They screw into the subfloor.

I thought Uhauls were the same? I haven't looked that close at any of them.
The U-hauls have the overhead cubbies glassed-in but the closets and cabinets have liners that come out - after 1984 according to the guide. I have had my closet out a couple times to pull wires. Makes a nice tub!

Regards,

Matt
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