Foil Bubble Insulation Methods

[2airishuman]

hi malcolm and others

your progress with the foil insulation is nice and from the pictures the technique is first rate. it's great that you've documented with so many pictures because once the interior is completed, no one will be know what you've done....maybe you need to do one spot of interior wall with a square foot of lexan....so folks can view the inner details....a see through inner wall?

as for the added tyvek type vapor barrier....given the outer skin, inner skin and wall covering that's about enough barriers. adding more would likely increase moisture retention issues....keep in mind we can add several quarts of water vapor to the insides just hanging out in the tube.....venting is just as important as insulation in an airstream.

mark
you suggested a thermal break at the rib/skin connection....i recently toured the factory (will post pics soon) and they are now using a thin "double stick tape like material" applied to the ribs/cross beams/supports before the outer skin is applied. apparently it hold the skin in place while the rivets are applied and gives the thermal break you suggest between the outer skin and support grid. i didn't see a second layer between the inner skin and inner surface of the ribs....i'll have to look at my pics, but i don't think they are using it on the inner skin.

i'm sure you all know the fiberglass insulation is r-11 and the foil r-19 so this added insulation factor is significant. of course it doesn't address the biggest heat loss issue....single layer glass windows.

don the tour guide said they are using the foil on all slides now. he suggested an entire coach could be done with foil as a special order, but i don't know if this is offical airstream info or just his opinion. since my unit was on the line and just 2-3 days from completion.....i didn't ask them to go back and change the insulation....but i thought about it.

anyway great job with the foil.
cheers
2airishuman

[markdoane]

Originally Posted by 2airishuman

hi malcolm and others

i'm sure you all know the fiberglass insulation is r-11 and the foil r-19 so this added insulation factor is significant. of course it doesn't address the biggest heat loss issue....single layer glass windows.

2airishuman

2air',

Not wanting to detract from the GREAT job Malcolm is doing, but I don't think the R-19 value is accurate. If you read the manufacturer's info, the R-19 is for Reflectix inside a 3 1/2" wall cavity with 3/4" wood sheathing on both sides. Thats a lot different than 1 1/2" with aluminum sheathing, since the air-gaps are a critical part of the system..

I think Malcolm has done a great job, but I wouldn't expect to get R-19.

[uwe]

Malcolm,

Thanks for the information. I really appreciate it.
Somehow I ended up tossing all the 40 year old insulation last weekend, just did not want it laying around the shop. Most of it was actually very clean, some of it not so clean, but none of it showed signs of rodent infestation or insect contamination.
Of course then came the " Now What" phase.....
Foil insulation it is!
Thanks again.

[w7toc]

Hi All:

What I have found in my own testing is that the system approach works best.

About 17 years ago I took a 1981 Ford E350 van and set off to make a 2 ¾ wall cavity as thermally efficient as possible. I used a coating called ENERCHRON V40 a radiant barrier coating, a tri-lament radiant barrier, and long-term R6 foam insulation. The system was as follows: metal wall coated with 10 mils (10 1/1000 of an inch) ENERCHRON V40, 1/8 air space, 3 layers of a tri-lament radiant barrier, R6 foam insulation, 3 layers of a tri-lament radiant barrier, 1/8 air space, back side 1/8 oak paneling coated with 10 mils ENERCHRON V40.

In researching the bubble pack, I found that in high temperature enclosed areas (about 210 degrees F.) the air in the bubble pack expanded to the point where the air escaped from the bubble pack. This would normally not be a problem, because the plastic that forms the air space and separates the aluminum would still allow the radiant barrier to work. For my experiment the problem was that if that happened I would lose too much space.

For those who are not familiar how radiant barrier works it goes like this: The radiant barrier is comprised of 2 layers of almost pure aluminum and a layer of non-conductive plastic which is sandwiched together. As energy is absorbed into the aluminum it is unable to pass through the non-conductive plastic. This due to the fact that, it is easier for the energy to release back to the open air space, than to pass through the non-conductive plastic. This is true only when the aluminum surface is clean. If dust build up becomes too high then the energy will find the path of least resistance, which is through the non-conductive plastic.

In the space of one layer of bubble pack you can fit 10 to 15 layers of a non bubble pack radiant barrier. Since I used a long-term R6 foam insulation as the non-conductive center, it was a more effective system than if I had filled the whole cavity with bubble pack.

Since the ENERCHRON V40 is painted on, I was able to thermally seal the entire wall including all the nooks and crannies of the metal wall. The ENERCHRON V40 has a very unique property, in that it does not lose its effectiveness when it gets dirty. This was very important because even though the wall was enclosed there is no way to stop the dirt that would migrate through the wall. Also, it has a low emissive level which depending on conditions greatly helps to slow the highest level of incoming energy.

The Net Result:

The van had 9 windows, of which 6 were coated with a black film, and 1 roof vent.

In the summer time with the roof vent cracked open and the van sitting in the sun the temperature in the van got no higher than the outside temperature, even in Arizona on days when the temperature reached 120 degrees F. In the morning there was no morning per-heat.

In the winter, the worst conditions I ever tested it in, was where the air temperature was 4 degrees F. below zero with a 35 mph wind (wind chill factor of -33 degrees F.). I used a 6” ceramic block heater with thermostat, which was able to maintain an interior temperature of 72 degrees F. In fact once the van heated (which took an hour and 19 minutes, from a starting temperature of 38 degrees F.) the heater started to cycle in about 22 minute cycles.

In the 11 years I drove the van I saw no loss in performance. I finally had to stop driving the van because of low fuel economy (with changes in fuel formulas and miles on engine at 268,000 I was only getting 6 mpg) which was a sad day for me.

So what I discovered was it is possible to reach thermal effectiveness at very low thickness levels, if you take the time to build the right system.

Rick

[malconium]

Originally Posted by markdoane

2air',

Not wanting to detract from the GREAT job Malcolm is doing, but I don't think the R-19 value is accurate. If you read the manufacturer's info, the R-19 is for Reflectix inside a 3 1/2" wall cavity with 3/4" wood sheathing on both sides. Thats a lot different than 1 1/2" with aluminum sheathing, since the air-gaps are a critical part of the system..

I think Malcolm has done a great job, but I wouldn't expect to get R-19.

I agree with Don. I am not expecting to get R-19 from the foil - just a better value than for 1-1/2" of fiberglass. I do think that only 1-1/2" of fiberglass will have way less than R-11 too. I don't know just how much difference the actual thickness of the air gap on each side of the foil makes in the overall approach. I have generally thought that the important thing was to have some air gap.

Malcolm

[malconium]

Rick,

Your approach sounds interesting. Can you give more details about product names and sources? Did you find your system to be somewhat expensive with all the layers? Of course we have only 1-1/2" to work with so we could not use as thick of a foam core. What do you think you would do for the thinner wall?

Thanks,

Malcolm

[malconium]

Originally Posted by uwe

Malcolm,

Thanks for the information. I really appreciate it.
Somehow I ended up tossing all the 40 year old insulation last weekend, just did not want it laying around the shop. Most of it was actually very clean, some of it not so clean, but none of it showed signs of rodent infestation or insect contamination.
Of course then came the " Now What" phase.....
Foil insulation it is!
Thanks again.

My old fiberglass wasn't too bad either. I did find one area above the right wheel well where there was some rodent evidence. This was in an area where I had a hard time understanding how a rodent could actually gain access.

Malcolm

[w7toc]

quote

"Rick,

Your approach sounds interesting. Can you give more details about product names and sources? Did you find your system to be somewhat expensive with all the layers? Of course we have only 1-1/2" to work with so we could not use as thick of a foam core. What do you think you would do for the thinner wall?

Thanks,

Malcolm"


Hi Malcolm

By the way, I have 1972 31' Sovereign that I am in the process of bringing back to life. It was on the road for only 2000 miles then spent the rest of its life parked in Carson City, Nevada.

The layering process was very easy and inexpensive the way I did it in my van.

What I did was: I cut all the foam board so that it fit in between the metal supports of the van (walls & ceiling), then I took the roll of radiant barrier and simply wrapped it around each foam piece 3 complete times. Remember the radiant barrier doesn’t work without an air space, so when I wrapped it around the foam I wrapped it very loosely. Then I taped the sides closed. Last I inserted the foil/foam panel into the ENERCHRON V40 coated areas.

The most time consuming part, was cutting the foam to size. The reason I taped the sides was to reduce dust build-up on the inner layers. You have to keep in mind that once the aluminum gets dusty two things happen; 1. The rate of energy flow into the foil increases, and 2. The energy flows conductively through the center material, making the product almost useless.

What I find frustrating is that the foil manufactures whose products I have looked at; only give “effective R values” on their products. This value is meaningless once the surface has dust buildup. What is the R value for the material in between the foil? That is what they need to also tell us.

When it comes to thermal coatings there are a lot of scams going on out there. Ceramic paints make R value claims of R 20 which are complete lies. A coating cannot have an R value. Due to the way that the R value tests are conducted coatings cannot be tested. WHEN LOOKING AT A COATING, MAKING THERMAL CLAIMS, BE SURE THAT IT HAS DOCUMENTED GOVERNMENT TESTING SHOWING ITS PERFORMANCE WHEN DIRTY!

I have found that the ENERCHRON V40 coating will stop condensation on metal surfaces. Even in my bathroom, which I coated, will not have water build up after a long hot shower. On my van, all interior rusting stopped when I coated it, which was a nice surprise years later when I inspected it.

The products I used:

The radiant barrier was a “no name” product I bought in bulk. It was 99% pure aluminum foil on both sides which was cold punched every ¼ inch. The middle was a Poly-Mylar that had a fiberglass rip stop scrim. I have not researched the new radiant barrier out on the market. It needs to be looked at if the foam center radiant barriers are worth the extra space they take up. My gut feeling is that more layers of a standard radiant barrier will be more effective. This needs to be tested.

The foam was another “no name” product I bought in bulk which was a rigid board that had a long term R 6 insulation value per inch. Back then that was the best available. Today you can get rigid board with an R 8 insulation value per inch.

The coating was ENERCHRON V40, whose web site is at www.enerchron.com . Check out their testing, very impressive.

Even with an inch and a half space I think that this system will greatly out perform any single insulation. As far as it performing as well as my van, the only way to tell is to test it out.


Malcolm I hope this answers your questions.

Best Wishes,

Rick

[Hit'nMiss]

Fascinating stuff here guys. Rick and Malcolm you guys are apparently true perfectionists and great believers in good documentation and the "scientific" method. I anxiously await further reports and good testing from Malcolm and others who improve outside the "box" er tube.

Travis in Maryland welcome aboard. Do not feel that you need to apologise for your participation or the length of anything you post on this forum, Actually when knowledge arrives brevity just gets in the way. But of course when the BS gets deep brevity takes a holiday. Most of us need good advice explained in lots of detail.

Malcolm your link above:
http://www.airforums.com/foru...ead.php?t=13363
does not work. I get a 404 error notice. Could you perhaps check it out. I guess you will have to have a moderator to edit it .

Insulation scams and confusion I guess are rampant in the world of everyone wanting to feel good about "conservation", saving the planet, etc. PT Barnum must be smiling from somewhere. I am amazed at the money folks in the south spend on replacing all the windows in their homes with the notion that the new ones will completely re-pay their super inflated prices with utility savings.
Yeah maybe in two lifetimes.
The dust on the foil theory is very interesting. If correct it makes even bigger mullets out of all those poor souls (like my ex-in-laws) who spent large sums to put huge sheets of aluminum foil in their attics. Eagle Shield I think it was called. Just laid up there helter skelter style and then they couldnt even go up there for any repair etc without making a total mess of the stuff. Actually couldnt even get in postion to check the installation very well. I have never seen an attic that didn't accumulate dust. But even dust free I think the foil in the attic was a scam.
I made the mistake of advising them what I thought and they always resented my opinion. They just thought that little sales gal was too cute to tell a lie. Ah the original garden blunder....eh Adam?

[w7toc]

HitnMiss

Thanks for the nice comments. I just wanted to say that the foil when clean DOES work. When the Government testing labs put out their original test reports on foil performance they did not take into account dust build up. As foil started being used for buildings they released reports showing the effect of dust/dirt build up. If you look the test report are out there. But as always, "BUYER BEWARE".

Rick

[malconium]

It looks like the addressing scheme for the older threads may have somehow changed. Try the following:

http://www.airforums.com/forum...ad.php?t=13363

Thanks for pointing it out.

Malcolm

[sara jane]

Hello there i am a wondering has anyone got a good brand you would go with for foil insulation in the Uk. I know reflectix is us and costs lots to get over. Any ideas. I am going for double bubble no trouble so any leads to brands would be much appreciated as is a mind field out there.
thankyou
sara jane
ps i dont have a Liner me got a 1950 cruiser

[VIKING]

Welcome to the forum sara jane.
I used a product called Prodex, from a website called www.insulation4less.com
Easy to use product. I think it's probably easier than reflectix and has better insulating performance, plus 19 db sound deadening. It may be more available to you , I'm not sure.
Good luck, Rich

[sara jane]

HEllo everyone anyone got any ideas of products to use from the Uk as there are soooo many out there double bubble i say sounds the least trouble.
so ifyou do know something thats alternative to your us premiums i would love to hear from you
all the best
tinkering ali
Sara Jane

[jcanavera]

Airstream used a foil insulation on the slide out Classics. I'm not sure if was in the floor only or dealt with the slide unit itself. They might have a spec on that. From what I'm aware the foil was used since it could provide equivalent R ratings as the fiberglass only batting, with less thickness.

Jack