Help me find a good class B or B+

[Davydd]

No, I am not associated with Advanced RV. I cannot be responsible either for the information they provide which is not up to date, IMO. I haven't seen any B with blue denim after mine three years ago in visits there and they install Tyvek which is not a vapor barrier. That one photo shows it. But again you cite unknowingly and refute anything I say. I stand by you being snarky because you do so every chance you get with me.

[BBQ]

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[booster]

Tyvek makes sense to me, as the whole thing is backwards from a house wall in the North. In the south, I am told the vapor barrier goes on the outside of the house.

The Tyvek will stop any water that hits it from getting to the insulation should there be a leak or spill, but still will breath enough to let the insulation dry out once the condensation conditions are gone if it gets damp that way. Steel bodied vans will get the wall, lined with Hushmat or not, plenty hot enough to dry out the insulation if the vapor generated can get out, as it would with Tyvek.

[avanti]

Originally Posted by booster

Tyvek makes sense to me, as the whole thing is backwards from a house wall in the North. In the south, I am told the vapor barrier goes on the outside of the house.

The Tyvek will stop any water that hits it from getting to the insulation should there be a leak or spill, but still will breath enough to let the insulation dry out once the condensation conditions are gone if it gets damp that way. Steel bodied vans will get the wall, lined with Hushmat or not, plenty hot enough to dry out the insulation if the vapor generated can get out, as it would with Tyvek.

Yes, Tyvek will do no harm, since it is indeed moisture-permeable. It HAS to be in order to avoid creating a second vapor barrier (which is ALWAYS wrong, even in a van which is "not stationary"). But it does no good, either, in this application. It is intended primarily to minimize wind washing, which cannot happen in a B-van. It has zero R-value. Yes, it will protect against liquid water, but so will the vinyl or wood finished walls. And, in any event, it is not particularly stable over time, as anyone who has removed the sheathing from an older Tyvek-treated wall knows.

I love ARV to death, and greatly admire their willingness to experiment. But there is a fine line between free-wheeling experimentation and ignorance of best practice. They certainly used to say that they used vapor barriers--I take them at their word, although perhaps they just didn't know what that meant when they were getting started. Whether a given owner will admit it or not, not providing a venting path on the opposite side of an absolute vapor barrier is an obvious rookie mistake. I am guessing that they have discovered and corrected the error.

[GeorgeRa]

Originally Posted by booster

Tyvek makes sense to me, as the whole thing is backwards from a house wall in the North. In the south, I am told the vapor barrier goes on the outside of the house.

The Tyvek will stop any water that hits it from getting to the insulation should there be a leak or spill, but still will breath enough to let the insulation dry out once the condensation conditions are gone if it gets damp that way. Steel bodied vans will get the wall, lined with Hushmat or not, plenty hot enough to dry out the insulation if the vapor generated can get out, as it would with Tyvek.

Having a single water vapor barrier for insulation is an accepted standard for insulation, van has one already, it is the steel chassis. Personally, I wouldn’t place Tyvek from inside because it will inhibit vapor diffusion in both direction, but Tyvek would be far better than water vapor barrier. Based on ARV written information and pictures I think ARV is using excellent Tyvek tape to attach a plastic foil which doesn’t look like Tyvek, Tyvek has markings and is sold in rolls. See this video youtube......com/watch?v=vHBpvyoRuO0

[booster]

The pic that davydd put up also shows the Tyvek tape, apparently on the Hushmat, so you may be correct. The pic you showed may be shiny plastic that is taped, but it also may be the Hushmat.

[Davydd]

Originally Posted by booster

The pic that davydd put up also shows the Tyvek tape, apparently on the Hushmat, so you may be correct. The pic you showed may be shiny plastic that is taped, but it also may be the Hushmat.

It's not taping over the Hushmat. Hushmat is self-sealing.

[BBQ]

.

A vapor barrier is used to keep moist air from reaching a cold surface.
Because once the moist air, no matter how "dry", touches a cold surface,
it will condense and turn to water.

The RV's steel outer skin is not a vapor barrier.

It is an exterior water barrier.

[avanti]

Originally Posted by BBQ

.

A vapor barrier is used to keep moist air from reaching a cold surface.
Because once the moist air, no matter how "dry", touches a cold surface,
it will condense and turn to water.

The RV's steel outer skin is not a vapor barrier.

It is an exterior water barrier.

If you check any of the standard references, I think you will find that this is not consistent with standard usage of the term.

But, it doesn't really matter what you call it. If you have a volume of space that is bounded by surfaces that are impermeable to water vapor, you are going to trap moisture permanently, with deleterious effect. An RV's steel outer skin and an internal plastic sheet are an example. If you could make a perfect vapor barrier, this wouldn't be true. But you can't.

[Technomadness]

Originally Posted by Davydd

All Advanced RVs since inception have as much insulation as you can practically add. There was a major difference in my Great West Van Sprinter and my Advanced RV in both insulation comfort and sound deadening. Night and day if for instance you might want to boondock in a Walmart parking lot.

My budget for a fully custom van would max at $200k, I assume that’s well below what an advancedRV costs, right?


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[Technomadness]

Originally Posted by mtmdatlanta

Avion talks a lot about their advanced Azdel insulation and 4-seasons construction, FYI.

Thanks. I’ll check them out. Their website is weak, but maybe I should pay them a visit. What I saw so far looks ok.


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[Technomadness]

Originally Posted by GeorgeRa

I insulated our DIY van back in 2013 with Thinsulate.



I am shocked that some vans have no insulation, but, I would prefer no insulation than dealing with consequence of bad insulation material like Denim or wool.

If I go the DIY route my plan is rattletrap or other tar like exterior sheet, then a couple inches of polyisocuranate, with DIY foam in the cracks. Probably have to use UHMW between the inner structure and the stringers to prevent heat transmission.

It’s too bad the stringers are so much deeper than the walls, as the heat loss from them alone kinda renders too much effort on the walls pointless.



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[Technomadness]

I really am tired of the constant attacks against advancedRV and davidyy- he owns one so he references it for referring to his experience.

Anyone who has spent an hour watching the advanced RV videos on YouTube can see they are very experimental, very scientific, and learning what it takes to make an RV to a level that other manufacturers aren’t trying.

Obviously that means they will make mistakes and evolve over time.

Personally I’m grateful people like David are spending the big bucks to fund this because the entire DIY movement benefits from what they learn at his expense! (And he gets to he on the cutting edge so win-win.)

This entire debate should have been about layers and the physics of vapor, not a criticism of ARV, which just detracts from any message you might have wanted.


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[avanti]

Originally Posted by Technomadness

I really am tired of the constant attacks against advancedRV and davidyy- he owns one so he references it for referring to his experience.

Anyone who has spent an hour watching the advanced RV videos on YouTube can see they are very experimental, very scientific, and learning what it takes to make an RV to a level that other manufacturers aren’t trying.

Obviously that means they will make mistakes and evolve over time.

Personally I’m grateful people like David are spending the big bucks to fund this because the entire DIY movement benefits from what they learn at his expense! (And he gets to he on the cutting edge so win-win.)

This entire debate should have been about layers and the physics of vapor, not a criticism of ARV, which just detracts from any message you might have wanted.

I assume you are addressing me. But I plead not guilty. I have repeatedly stated how much I admire ARV. I couldn't agree with you more about how much they have benefited the DIY community. I have stolen a number of ideas from them, including using the Espar coolant for freeze prevention, much of my electrical system, the installation of a Bird View camera, and more. I have always tried to credit them when I have done so. Their openness with their ideas is truly admirable.

But, their mistakes are as valuable as their successes (as is true of all of us). It is not an attack to point to an isolated error, especially one that they have corrected. It does no good to blindly accept everything they do, right or wrong.

If I have come across as if I think otherwise of them, it is not my intention.

[GeorgeRa]

Originally Posted by Technomadness

If I go the DIY route my plan is rattletrap or other tar like exterior sheet, then a couple inches of polyisocuranate, with DIY foam in the cracks. Probably have to use UHMW between the inner structure and the stringers to prevent heat transmission.

It’s too bad the stringers are so much deeper than the walls, as the heat loss from them alone kinda renders too much effort on the walls pointless.

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I would stay away from any product which would emit VOC like tar. 2” of foam would be very good but difficult in a van which has limited flat places, a lot of inner steel structures. Using foam in cracks could cause VOC, especially the DIY type and likely external metal distortion.

In my opinion foam sheets are great for insulation but van's nooks and crannies are difficult. I picked on Thinsulate because it is very easy to install, no loose fibers, no VOC, has decent insulation and sound blocking qualities.

Good insulation is also full foam in situ done by real pro, rarity. The issues are external metal buckling and VOC.

Best for 4 seasons would be a C -RV with flat wall insulation sandwiches done on a factory press. I had 4 season Bigfoot trailers with 2.5” inches of foam and loved it, just too bad it was a trailer.

Wherever you go for your van, insulation wise you should be in the driving seat. If you plan to have aluminum framing make sure to use thermal breaks between the chassis and Al framing. In my O/H cabinets I used structural fiberglass angles.

Building a DIY is like building a prototype, one and only one, it is rare to come back and get improvements into a second or a third one and definitely not a production unit, so I had my share of oppsies, it is life. But, Thinsulate would stay for a never happening production unit.

https://www.youtube.com/watch?v=dq671waCndc

[Davydd]

Originally Posted by Technomadness

My budget for a fully custom van would max at $200k, I assume that’s well below what an advancedRV costs, right?


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They have a few low mileage vans below $200 grand with features unavailable at any other company at:

https://advanced-rv.com/available/

They have pretty much bought back vans from customers under various circumstances and there are quite a few on their second Advanced RV. Sue Valentine, whom you may know on Facebook if you follow Class B groups, went this route originally and is now getting her second ARV being built and she cancelled an order for a Winnebago Revel. She impresses me as very cost conscious. A lot of people who buy those available ARVs have them upgraded and customized for their needs because Advanced RV talks to their customers. You don't go through middleman dealers or salesman making commissions.

The "experts" here will only tell you the cost of the most unique ARVs. They have no idea what the true cost is. I paid under $200,000 for Alvar new and I got exactly what I wanted with no compromises. Keep in mind most ARVs are loaded with features their customers want that you cannot get from other companies at any cost. You have to talk to them directly. I have no idea what other customers paid for their ARVs as it is not my business. I don't even know if they negotiate on those stated prices.

[Technomadness]

My comment was addressing the general tone of a number of responses, not any specific person.


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[Technomadness]

Originally Posted by GeorgeRa

I would stay away from any product which would emit VOC like tar.

In my opinion foam sheets are great for insulation but van's nooks and crannies are difficult.

Best for 4 seasons would be a C -RV with flat wall insulation sandwiches done on a factory press.

If you plan to have aluminum framing make sure to use thermal breaks between the chassis and Al framing. In my O/H cabinets I used structural fiberglass angles.

Thinsulate is not something I’m opposed to but I’m missing the advantages of it over polyisocuranate. Seems more expensive and thinner.

At any rate it’s the nooks and crannies and the structural sheet metal ribs/supports that’s the challenge. I understand the buckling issue can be fixed by using foam that expands less? Window sealant I think?

I’m kicking around the idea of making a unified wall structure that doesn’t try to fit the curve if the van wall. Just straight up for so many feet then a fixed angle for so many feet to the ceiling. I can insulate that, and fit it to the sides and leave air gaps in the rib space or just fill those and not worry about the nooks and crannies. Basically a shell wishing the van body, structurally connected to it, thermally isolated. I would lose two inches of width for every inch of insulation, but it could be pretty modular. 80/20 May make this easy to build. Not ideal but it might be worth the tradeoff for build optimization.

The more I think about it the more I’m convinced this needs to be four season capable and I am gonna have to DIY. If I’m going that route I’m going to design for replication. So if the van is totaled I can recreate it very fast, even use the modules in the next van. This may not be practical but looks like it is at this point. Won’t be able to tell until I have the van in hand.

I saw someone using fiberglass angle to isolate internal structural aluminum from the van structure and was stealing that idea, only my thought is to use UHMW. UHMW is polypropylene of high molecular weight, and can be worked like wood, is electrically and thermally jnsulating but not rigid and brittle like fiberglass angle can be. (Tears rather than sheers). It might be a bad idea but I’ve worked with it in very high stress environments before— battlebots— and it can take a beating from an opponents weapon.

By the way, I’m pretty Ute the guy I saw using Fiberglass angle mentioned he got the idea on the sprinter forums from a George, so maybe that was you— it’s a great idea!

I agree best for insulation would be a class C with well made insulation. Good structural integrity could come from vacuum forming or solid fiberglass. If Bigfoot we’re still making motorhome a id be keen on that. I have considered remodeling an older fiberglass RV, but that’s looking like several weeks to get to the point where I can start building. (Eg have to tear out the interior, clean and repair it etc.)

Anyway, having looked at a bunch of RVs, right now when I see a TRAVATO (about $80k Street price) I figure it’s worth the $40k over the cost of a bare pro-master to do it myself.

Though I’m torn. I’d rather buy than build, but I’d rather spend the time doing it right upfront than deal with the consequences of their low quality down the road.

My mistakes will be a lot more fun to deal with than theirs!


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[Davydd]

For once I agree with GeorgeRa about foam insulation. Even Advanced RV tried it and removed it from a van because of skin distortion.

Typed with GoAbout an intelligent responder when you are away from your iPhone.

[GeorgeRa]

Originally Posted by Technomadness

My comment was addressing the general tone of a number of responses, not any specific person.


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You are correct about the general tone, forums are places for folks with common interests to share their views, sometimes strong, sometime agree, sometime agree to disagree. My threshold point is name calling, it could be “it is a lie”, “stupid”, at these points built into my DNA ROI triggers, why, life is too short.