Insulation Advice

[Synel]

Good morning.

I need clarification insulation in custom builds. Specifically, the M820 expansible camper (I am aware of the difficulties with the expansible part.) Trying to convert it into an RV but I want to add four layers of insulation, starting maybe with dynamat, UHMWPE, aerogel, rockwool and then the interior wall (~2 inches of insulation.)

I can't find any concrete step by step guide on how to insulate though I do know that you should use foam filler for corners and cracks and you should have some kind of vapor barrier. Aside from that, I'm looking for as much advice as possible.

Thank you in advance if you can help.

 

[SolaAesir]

Look into the ways that people insulate cargo containers. Your primary concern is going to be with moisture/condensation. I believe spray foam is the most highly recommended option.

 

[chucky]

Spray foam will serve you better over the long term ! Just pre run any wiring/ plumbing ect . before you spray !

 

[ckouba]

What benefit are you expecting from Dynamat and the PE?

I believe Dynamat is acoustic attenuation, and it'd be a LOT of extra weight, likely without much benefit.

If you're familiar with an UHMWPE which has good thermal insulation properties, go for it, but I do not think it's a feature of the material. They are good electrical insulators though. What are you planning to use?

Aerogel is expensive, but buy once and cry once. I imagine you'll be happy long after.

I used the pink foam at 2" thickness with the Lizard Skin as a base. It's been fantastic in a 22' x 8' box. Reasonable on budget and has been warm when heated in the winter, and remains reasonably cool in the summer (no A/C installed yet).

 

[Synel]

What benefit are you expecting from Dynamat and the PE?

I believe Dynamat is acoustic attenuation, and it'd be a LOT of extra weight, likely without much benefit.

If you're familiar with an UHMWPE which has good thermal insulation properties, go for it, but I do not think it's a feature of the material. They are good electrical insulators though. What are you planning to use?

Aerogel is expensive, but buy once and cry once. I imagine you'll be happy long after.

I used the pink foam at 2" thickness with the Lizard Skin as a base. It's been fantastic in a 22' x 8' box. Reasonable on budget and has been warm when heated in the winter, and remains reasonably cool in the summer (no A/C installed yet).

Hey. Sorry for the delayed reply.

I was recommended to use the dynamat by several of my coworkers. Originally the plan was the UHMWPE to combo with the aluminum shell. The aerogel was the major contributor for R value and then rockwool for extra sound proofing.

I was shooting for somewhere in the area of 10-13. The ceiling I need to push that up a bit. From what I've read you want somewhere in the area of 20 for the ceiling. I'm still iffy on whether I want to insulate the floor but, if I did I would shoot for 10 there as ell.

Those same coworkers did recommend lizard skin as well but in place of the dynamat.



Thanks for the replies overall by the way. Whenever the project gets underway in earnest I'll see about taking pictures of the process.

 

[ckouba]

I gave very little consideration to acoustic abatement and have no issues getting a peaceful night's sleep. I'd be skeptical of needing it unless you're camping somewhere noisy, which rather defeats the point of getting away from it all. Obviously it's up to you but for the weight it would add, I would skip it.

Is the PE supposed to be thermal insulation? I haven't seen a version of it which offers that as a benefit, although I haven't looked too hard into it.

I would absolutely recommend insulating the floor, with the goal of getting all your tankage inside the thermal insulation envelope. I see you're in AZ, but even up north there, I've been in snow and ice. Now is the time to build it correctly as it will be painful to go back and add it later.

 

[TechnoWeenie]

Good morning.

I need clarification insulation in custom builds. Specifically, the M820 expansible camper (I am aware of the difficulties with the expansible part.) Trying to convert it into an RV but I want to add four layers of insulation, starting maybe with dynamat, UHMWPE, aerogel, rockwool and then the interior wall (~2 inches of insulation.)

I can't find any concrete step by step guide on how to insulate though I do know that you should use foam filler for corners and cracks and you should have some kind of vapor barrier. Aside from that, I'm looking for as much advice as possible.

Thank you in advance if you can help.

Tiered insulation is a great way to create space for water (vapor+condensate) to get trapped.


You're better off gutting everything, sealing everything, then look online for some low cost spray foam installers in your area - they're usually out of a trailer or something - then offer to bring it to their shop. The labor/time to shoot it is minimal compared to prep and finish work.

2" of closed cell foam will act as a vapor barrier.

 

[hike]

Tiered insulation is a great way to create space for water (vapor+condensate) to get trapped.

Finding the dew point locations in a wall section for all likely temperature differentials and humidity directions is important—

 

[TechnoWeenie]

Finding the dew point locations in a wall section for all likely temperature differentials and humidity directions is important—

Spray-in closed cell foam that's at least 2" negates that issue.

 

[87cr250r]

Right. Corrosion under insulation is a specific engineering problem. It's caused by insulations that breathe. Closed cell foams don't breathe but you need to treat them like a paint and prep surfaces so that they coat like a paint. Other types of insulations need some type of encapsulation. This can be as simple as tape.

There is no one step solution here. Be more specific about what you want to achieve.

 

[hike]

Spray-in closed cell foam that's at least 2" negates that issue.

We agree, though there is more to consider.

Spray foam is only one component of a wall. You are right: condensation will not occur within closed cell spray foam and it does act as a moisture and vapor barrier itself if well sealed at the through points. A wall is more than insulation alone, typically. What is the insulation clad within? The key to fighting condensation is to make sure the dew point location is either: within a wall space where no moisture can condense, (closed cell foam, for example); or outside the wall's cladding, preferably outside the conditioned space.

There are many ways to combat condensation, the key is finding where the dew point location occurs during the seasons and managing the materials at those locations to either thwart condensation or mange it well—

 

[Synel]

Thank you again for the replies. I've tried some research into the issue and the dew point factor is essentially the direct "point of failure."

But I also think that can't be eliminated entirely, and I don't think I want to try and heavily deal with differing layers of insulation and manipulating it to the one point where it can be dealt with.

I think I'm going with a high R value insulation nearest the exterior wall, but I'm gonna try and make sure there's a intake/exhaust system for ventilation to minimize the humidity.

Or at least that's part of the system at this point.

Reading through this and other sources:

Condensation in Van: Why It Happens and How To Manage It - FarOutRide

Condensation is part of vanlife. But too much, too often, is an invitation to mold and rust! Here's why it happens and how to manage it.

faroutride.com

Edit:
Also, the plan is to gut the interior to install a fresh insulation system. Basically starting from scratch outside of the aluminum shell.

 

[hike]

Thank you again for the replies. I've tried some research into the issue and the dew point factor is essentially the direct "point of failure."

But I also think that can't be eliminated entirely, and I don't think I want to try and heavily deal with differing layers of insulation and manipulating it to the one point where it can be dealt with.

I think I'm going with a high R value insulation nearest the exterior wall, but I'm gonna try and make sure there's a intake/exhaust system for ventilation to minimize the humidity.

Or at least that's part of the system at this point.

Reading through this and other sources:

Condensation in Van: Why It Happens and How To Manage It - FarOutRide

Condensation is part of vanlife. But too much, too often, is an invitation to mold and rust! Here's why it happens and how to manage it.

faroutride.com

Edit:
Also, the plan is to gut the interior to install a fresh insulation system. Basically starting from scratch outside of the aluminum shell.

Thoughtful article, thanks for sharing

I have been wondering in your case starting from the outside in:

sealing exterior,
van box skin,
lizard skin on inside of exterior skin (would help seal potential leaks and provides a ceramic thermal barrier),
closed cell foam between structural elements,
furring strips over structural elements (already covered by lizard skin),
interior finish (not vapor barrier type)

may be best?

Then as the article and you say: active heating and venting.

Let us know what you do, and photos are always enjoyed—