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Old 10-17-2017, 11:41 AM   #21
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Got a link?
here

Part of his issue was using thin ceiling tin to cover windows.

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Old 10-17-2017, 01:57 PM   #22
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I wonder to what degree the oil canning was a result of foam mechanically pushing the metal out, versus the heat from the exothermic reaction causing the metal to heat and expand.
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Old 10-17-2017, 02:36 PM   #23
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I wonder to what degree the oil canning was a result of foam mechanically pushing the metal out, versus the heat from the exothermic reaction causing the metal to heat and expand.
Its not from metal expanding. that takes a LOT of heat.
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Old 10-17-2017, 03:11 PM   #24
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[QUOTE=Tedd;229780]
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Originally Posted by Pygmy Yeti View Post
At the 1:50 mark, they show adding the foam with the old insulation left in. Very interesting. I'm calling these guys tomorrow. If there are no problems, I am certainly going this route. /QUOTE]

Neat vid. This stuff has a lot going for it. From the vid it looks like the foam would collapse and encapsulate the existing batts of insulation just fine.

Make sure to tell them that the roof and ceiling material is nearly paper thin, not very rigid and non supported areas can be as much as 36 ins. across.

And try to get an idea of costs.
I can't tell if the foam they use is closed or open cell. It doesn't appear to say on the website, and google didn't help.

There is another company that does this work too, and their R-Values seem higher.
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Old 10-17-2017, 03:12 PM   #25
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I wonder to what degree the oil canning was a result of foam mechanically pushing the metal out, versus the heat from the exothermic reaction causing the metal to heat and expand.
This foam doesn't expand. It is fed in with the consistency of shaving foam, and sets in place.
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Old 10-17-2017, 03:54 PM   #26
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Not having followed the Transcendence build, I had to do some digging to actually lay eyes on the bulging. I found the post there which embeds the video episode 25, application of the spray foam. Didn't find any mention of the bulging from there to the current end of the thread, but I did find episode 41 which mentions the new exterior paint and gives a few glimpses of the exterior surface.

Some lines visible on the exterior look like they're telegraphing the location of the interior horizontal wood straps (example: episode 25, 3:35, note the location of the straps relative to that little window on the left side. In episode 41, 5:53, note the line visible front to back at about that same elevation). That effect would likely be from the force of the foam expanding behind the wood strap.

That said, there's other more random-looking ripple in the skin that to me looks heat-related. This past summer as I hung new skin on my bus I was surprised at how little heat it takes to put some ripple in even a 16 gauge strip. Just a few seconds of brushing the flame of a propane torch (the same I use for sweating copper pipe) could make the metal move visibly. About the same time in episode 25 one may note that the applicator's technique laid the foam heavy around the perimeter of each space, then filled the center. I submit that may have something to do with the ripples that are visible outlining the spaces from the outside. In these areas expansion can't explain what's seen on the exterior.

Perhaps heat and expansion both play roles.

In any case: we probably all agree it doesn't take much movement to make a visible bulge in these large sections of sheet, and it doesn't take very many pounds of force to produce that movement. IMHO injection of foam into a closed wall cavity would have a high opportunity for bulging the walls like a marshmallow, even if only slightly. To control the effect would surely require careful measurement of the space, metering of the foam, and a soft/low-expansion material. While I don't dispute that it's possible, I expect it's unlikely to be done at a price point most of us DIY skoolie-builders would go for.
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Old 10-17-2017, 05:26 PM   #27
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A couple of observations:
) That stuff looks like it's non-expanding. That would be a real advantage in the use case we're talking about.
) The insulation in a bus wall or roof isn't paper-backed. Still worth doing the experiment, but I would not draw conclusions from the video.
) My parents got a similar treatment done to their old house in the 80's. (The 2" hole saw and the hammered plugs look like what happened to our house.) The place got warmer and less drafty very quickly, but we got hairline cracks all over the wall, and that wall was old school plaster-and-lath. Not sure if I can claim any similarity to this situation, but that seemed to be a lot of force to me.
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Old 10-17-2017, 09:09 PM   #28
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I have talked to a few contractors that specialize in this stuff and they don't seem too eager to try something new. They usually don't even stage a job on a house for under $2500. I offered to pre-drill my access holes and drive the bus to them. They didn't budge.

Doing any sort of experimental trial run would necessitate using the exact product that will ultimately be used. Each company has their own recipe and with no fish on the line, none are offering any trial product.

Finding a DIY kit is tough. Spray foam isn't hard to get but injection seems a different story as it looks as if there are a few more moving parts.

If bulging is such a concern, I would think pre-drilling two holes per void (opposite ends from each other). That way there is an exit for over-swelling.

After talking to few people, a major concern is that you are still left with the inner metal skin that transfers heat from the outer skin via the ribbing. I suppose you could veneer over that with some wood, upholstery, etc.

I guess I'm just overly dreading popping all of those rivets out. Anyone have a de-riveter tool for sale?
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Old 10-17-2017, 09:14 PM   #29
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Here is some insight on the topic from a Reddit user named, Wavefunctionp.

That it a great idea. I think it'll be mostly wasted though. The heat will conduct through the metal, which is why most insulation installations you see on schoolies are ineffective. When you see people gluing reflectix to the walls, you know the person hasn't done much research. Or even bother to read the directions for the products they are using. You need a continuous barrier to break the thermal conduction/radiation. Stuffing of pouring into the crevices in vans and schoolies are wasted for this reason.
To put it into perspective, imagine a dutch oven with lid on a hot stove. Do you think stuffing the oven with insulation will keep you from burning your hand on the top? Ofcourse not, the heat just conducts through the metal and into the lid, the insulation only had a minor if any measurable effect on the lid's temperature.
A bus or van is just like that oven.
i still propose that something close to iseal would be very similar to that used in automobiles, which makes sense, because it is designed by engineers.
Use a rigid board material with moderate insulation properties like thin rigid foam, cardboard or plastic. Cover it with a layer of insulation like low density foam or thinsulate, and wrap it with a decorative fabric or vinyl. Fasten with those screw on button snaps for easy removal and cleaning. You could even get fancy with pleats or pillowing, since it is basicly an uppolstered panel.
Here's the basic idea on a van.

The guys in the 70s with custom van upholstery had the right idea. You want to cover the metal with as much continuous insulation as you can. Stuffing it in walls and ceilings doesn't do all that much.
The great thing about this plan is that you can do it at any time, you don't need to strip the bus down to the ribs. Really just only rip up the old floor, clean and seal it, and put down the new floor and start framing out. You can add the uphostered panels later since they would be easy to put in or change later. It'd be a finishing step instead of a structural step.
And since it is so common, not that you mention this in particular, I always mention that the ceiling panels are structural depsite what many people may say. They wouldn't be made of expensive metal and riveted if they were not. They make a huge continuous box beam arch. Taking it is out like like removing one of the sheets of the side of a piece of cardboard leaving only the other sheet and the corrugations....much flimsier now right?....same deal. A person may decide that it is still safe enough, and that's fine, but it is still MUCH less safe than stock.
If I didn't go with the upholstered panels thing, my second option would removing the ceiling sheet metal, studding the walls and placing wood standoffs on the ceiling, and then spray foaming the entire interior continuously. I would only do that if I KNEW I was going to be spending a LOT of time in cold climates for extended periods.
I still maintain that the best strategy for a bus is to plan to chase good weather, and have backup plans for the odd times it's not. Building for extremes is planning to add a bunch of complexity and cost to your build. Best to embrace the 'bussiness' of the bus first and adapt, instead of trying to make a bus into a climate controlled modern home.
Another minor quibble. I see people placing vapor barriers all the time. I don't know what they think they are doing. The sheet metal will block the transfer of vapor....their yeti thermos is prove enough of this. Anywho, stop with vapor barrier people, and if you are concerned about moisture....don't use a unvented propane heater like a little buddy, wave, or the like. You are going to be drenched. You are going to get mold. If you have need for extended periods of heating, put in a proper rv heater or a wood stove.
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Old 10-17-2017, 09:45 PM   #30
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Good post Pygmi Yeti.

The problem with "chasing the good weather", is that it will always be either too hot, or too cold for life in a tin can ... except maybe in New Hampshire on June 17th.

So one way or another we do need to insulate ceiling, walls, and floor.

Your point about the structural strength of the shell is well taken, and I doubt many would disagree. The counter-point is simply that even the compromised shell is still vastly superior to an RV, and a school bus has other designed in features that add to the safety aspects, most notably the raised floor. When I drive up behind a school bus in the Taurus, my head is about level with the feet of the kids sitting in the back. If I hit the bus, I am going under it.

Nonetheless, retaining as much strength as possible plays to the reasons we buy the things in the first place, and in a rollover I'd like as much strength in the roof as possible.

So how do we insulate effectively and retain the strength? Both being desirable.

The standard way is to remove the ceiling, spray foam or add rigid panels then fur over the braces before adding a wooden ceiling. The furring provides a thermal break, although not nearly the same R-value as we have in the voids.

One way would be to leave the ceiling in place and use construction adhesive to bond rigid insulation to it, then more adhesive to skin a new ceiling from plywood, or the lumber of your choice. It would cost some ceiling height, but offer a fully insulated roof with zero thermal conduction paths. Add a fresh layer of bus kote and that roof should suffer little in the way of condensation as well as keeping much of the heat outside. With a 78" headroom bus, that would probably be a reasonable solution without a roof-raise.

A ceiling done this way would still provide sufficient support for dividing walls if they were adequately tied to the floor and walls ... and still much better than a Class A motorhome.

The other option would be to add the insulation above the roof, but right now I can't think of how to make that practical.

The current approach to the walls seems to work quite well, especially if attention is paid to how the ribs are furred out.

A fully floating floor, maybe with a little adhesive to prevent is moving up and down, takes care of the floor ...

I dunno ... food for thought.
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Old 10-17-2017, 10:00 PM   #31
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If you use an air chisel and a decent compressor the rivet removal isn't bad.
Nothing to be scared of.
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Old 10-17-2017, 10:00 PM   #32
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So many engineers in one place.

Take the ceiling down, remove the gross insulation, spray the foam, cover ceiling up.

The ceiling tin does add *some* rigidity, but so does spray foam. My advice would be not to roll the bus for best results. If you do, the cabinets, stove, water tank will be much more of an issue than the removed tin.

Spray foam guys are aware of the Ziebart system, but they don't try to shoot into a wall cavity thru a hole. When you spray foam, you gotta keep that sucker flowing or it clogs. You don't have the luxury of poking around little holes and spraying a circular motion.

If you are dead-set on being a Guinea Pig, there are services that will drive a loaded spray truck to your door, tutor you quick, set-up their rig and let you shoot your own foam.

Part of the beauty of removing the tin is you can run wires up n over.
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Old 10-17-2017, 10:02 PM   #33
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So many engineers in one place.

Take the ceiling down, remove the gross insulation, spray the foam, cover ceiling up.

The ceiling tin does add *some* rigidity, but so does spray foam. My advice would be not to roll the bus for best results. If you do, the cabinets, stove, water tank will be much more of an issue than the removed tin.

Spray foam guys are aware of the Ziebart system, but they don't try to shoot into a wall cavity thru a hole. When you spray foam, you gotta keep that sucker flowing or it clogs. You don't have the luxury of poking around little holes and spraying a circular motion.

If you are dead-set on being a Guinea Pig, there are services that will drive a loaded spray truck to your door, tutor you quick, set-up their rig and let you shoot your own foam.

Part of the beauty of removing the tin is you can run wires up n over.
Insulation post of the year!
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Old 10-17-2017, 10:05 PM   #34
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Insulation post of the year!
Not really.

This is an interesting discussion that you can add to if you want

None of the usual methods do much to address the issue of thermal bridging through the ribs in the ceiling. Plywood furring is a poor compromise so it's worth exploring possible alternatives.
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Old 10-17-2017, 10:08 PM   #35
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Not really.

This is an interesting discussion that you can add to if you want

None of the usual methods do much to address the issue of thermal bridging through the ribs in the ceiling. Plywood furring is a poor compromise so it's worth exploring possible alternatives.
How does leaving the tin in-place address thermal bridging? Did you see the informal study I did with the IR thermometer?
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Old 10-17-2017, 10:12 PM   #36
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So many engineers in one place.

Take the ceiling down, remove the gross insulation, spray the foam, cover ceiling up.

The ceiling tin does add *some* rigidity, but so does spray foam. My advice would be not to roll the bus for best results. If you do, the cabinets, stove, water tank will be much more of an issue than the removed tin.

Spray foam guys are aware of the Ziebart system, but they don't try to shoot into a wall cavity thru a hole. When you spray foam, you gotta keep that sucker flowing or it clogs. You don't have the luxury of poking around little holes and spraying a circular motion.

If you are dead-set on being a Guinea Pig, there are services that will drive a loaded spray truck to your door, tutor you quick, set-up their rig and let you shoot your own foam.

Part of the beauty of removing the tin is you can run wires up n over.
Well we were discussing "injecting foam", and yes, they absolutely do inject through small holes into cavities.

What I can't work out is what kind of foam it is, and in a bus that matters. So I remain unconvinced, even though the system works without expanding foam, until someone can tell me it is closed-cell foam. Open cell, in a bus roof, seems to be a recipe for disaster.
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Old 10-17-2017, 10:13 PM   #37
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How does leaving the tin in-place address thermal bridging? Did you see the informal study I did with the IR thermometer?
You can add sheet foam insulation unbroken, from front to back by sticking it to the ceiling.
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Old 10-17-2017, 10:23 PM   #38
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You can add sheet foam insulation unbroken, from front to back by sticking it to the ceiling.
Have you looked at the inside of the bus ceiling yet? I don't know where you get 32' long sheets of foam, but I'd bet they'd be a bear to curve and apply.

You are overthinking it. I understand the topic is injected foam and I am saying, it's not a good approach for this application. I can buy a billet of steel and mill it to make angle iron, but why? You don't need to reinvent the wheel on this.

Blue Bird sprayed my bus with foam before it was placed on the frame. That is the best way to do it.

Second best is remove interior paneling and spray. Put sheets on the floor. If you want moar insulation, add sheets.

Do you know why the Industry calls it Rigid Foam? My first experience with spray foam was in 1974 when my dad had it installed on our house in Tucson.

Like I said, let us know your results.
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Old 10-17-2017, 10:31 PM   #39
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Have you looked at the inside of the bus ceiling yet? I don't know where you get 32' long sheets of foam, but I'd bet they'd be a bear to curve and apply.

You are overthinking it. I understand the topic is injected foam and I am saying, it's not a good approach for this application. I can buy a billet of steel and mill it to make angle iron, but why? You don't need to reinvent the wheel on this.

Blue Bird sprayed my bus with foam before it was placed on the frame. That is the best way to do it.

Second best is remove interior paneling and spray. Put sheets on the floor. If you want moar insulation, add sheets.

Do you know why the Industry calls it Rigid Foam? My first experience with spray foam was in 1974 when my dad had it installed on our house in Tucson.

Like I said, let us know your results.
All good points, but we are still discussing options and opinions either way are useful.

32' sounds to me like 4 x 8' sheets butted end to end and taped.

Yes, the sheets will take a curve very easily. Set the table saw to the correct angle and bevel the edges of 12" wide strips for the sides of the roof.

The two problems I can see to this approach are that the final covering won't be quite as strong as a screwed in ceiling, but construction adhesive is very good, and ceiling height will be reduced some.
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Old 10-17-2017, 10:47 PM   #40
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All good points, but we are still discussing options and opinions either way are useful.

32' sounds to me like 4 x 8' sheets butted end to end and taped.

Yes, the sheets will take a curve very easily. Set the table saw to the correct angle and bevel the edges of 12" wide strips for the sides of the roof.

The two problems I can see to this approach are that the final covering won't be quite as strong as a screwed in ceiling, but construction adhesive is very good, and ceiling height will be reduced some.
I consider butted and taped to not be unbroken. The issue is the ribs- are you spanning that gap, leaving a void? You are correct in not wanting to loose any headroom unnecessarily.

Ok, I went-out and took a picture of my ceiling. Even if you cut the foam neatly and kerf-cut the back, you will never match the efficiency of a liquid in hugging a contour.

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