Insulation?

There was a great thread a few months ago about different approaches to insulating the interior walls. I did a search but haven't been able to find it, so if someone has a link I'd appreciate it.

Originally I was planning on using fiberglass batting but that thread pointed out how those bats retain moisture, eventually causing rust from the inside out. Not good, obviously. I will be doing my interior in the next few months so I need to refresh my memory on the alternatives.

Also, after I finish rewiring everything I was planning on using that spray foam insulation in all of the structural ribs and anywhere else I can insert the nozzle, to try and seal everything up as much as possible for sound deadening purposes. Any reason why this might not be a good idea?

Fiber glass insulation has been known to trap moisture which leads to rust, true.
Spray foam traps moisture which leads to rust also.
Spray foam can expand and distort panels if too much used.
Spray foam is impossible to remove.

The problem of trapping moisture has less to do with the insulation used and more to do with. #1 external leaks allowing water ingestion. But mainly #2 lack of air flow inside the wall panels and a build up of condensation.

If you are truly concerned about corrosion, then spend time thinking about the inner walls ability to dry out. One good idea is to leave air space top to bottom inside the wall. Stop the insulation about 1" short of the floor.

People have experimented with "vapor barrier”, the problem here is vapor barrier is to be at the heat side of the insulation. Seeing as the van could be left is the hot sun, or out in cold weather, which side is the heat side of the insulation? The vapor barrier will become a moisture trapping seal.

In aircraft this condensation entrapment and corrosion is a large issue. Aircraft exteriors experience extreme temperature changes several times a day. Combine that with all the people stuffed inside giving off moisture and you have what amounts to "a still" condensing water that flows down the walls. Some larger aircraft have an air flow and water removale system specifically for keeping the cabin wall interior dry.

Vans will not be like aircraft for condensation production but the principals are the same.

If you are concerned about corrosion causing condensation entrapment think about these processes. In aviation the fiberglass insulation is attached the wall panel boards and not to metal surfaces anywhere. In some instances the fiberglass insulation is inside a sealed plastic bag and placed into the cavity with a snug fit. There is usually small slit openings in the panels to let air in and out of the wall structure and the insulation is not allowed to touch the floor panels where water may accumulate and need to dry up.

If sound is the issue, smaller pieces of sticky tar paper are attached to the middle of larger exterior pannels and that stops the tin can sound dead while letting the metal surface breath. You don't need or want to cover the whole pannel. You can get the sound deadner at the local hardware store.

Automotive manufactureures insulate higher end vehicles in this same manner, thin insulation attached to the interior pannels, tar paper patches attached to the exterior steel pannels, including fiberglass incapsulated in sealed plastic bags. They do used (not vapor barrier) but moisture barrier in certain locations but those locations always have drain holes at the bottom of the cavity and the moisture barrier is to keep the maoisture off the insulation.

The single biggest corrosion causing problem in these old vans is a lack of stratigicaly placed body drain holes leaving much trapped moisture, water and mud.

Choking your van up with foam insulation is a garanteed slow corroding death for the poor thing. The walls have to breath man!

M1D

A good read m1dadio. Thanks!
I'm hoping to do something with the interior of ours soon too.

Thanks for the link Dix - that was the one!

Great info M1. You've convinced me to forget the spray foam!

Doug is offering insulation kits for A-100s and others on the Yahoo site with a year-end discount....

people stuffed inside giving off moisture and you have what amounts to "a still" condensing water that flows down the walls. Some larger aircraft have an air flow

After considering all of this, and taking a good look at the insulation options at Home Depot and Lowes, I think I'm getting close to figuring out what I'm going to try.

Lowes has what I think others have described as a thin metal foil covered plastic/air pocket combo. Very thin, and in my opinion not enough.

I think I'm going to use the 'styrofoam' sheets, glued to the back of the side and top finish sheets of wood, but done in a way that they never contact the side sheet metal or the ribs. This should give me some air circulation and prevent squeaking from rubbing against the styrofoam (although I must admit the stuff I found didn't seem prone to having sqeaking issues, a major consideration for me).

I'll staple the foil insulation on top of all that to seal it up better, leaving some room at the top and bottom for it all to breath.

I am still concerned about getting rid of the tin can sound, since the insulation shouldn't be touching the sides, especially the roof. I saw the suggestion about tar paper strips on only part of a sheet metal section, but I'm not sure what these strips are, and where you can purchase them. Hard rain used to be the worst, and once I crammed household insulation in my old A100 it made all the difference. Bad idea, I now know, but I remember how much quieter everything was once I insulated it.

The noise from the sheet metal comes from the fact that they resemble a speaker being a lerger surface area that can vibrate and reverb the noise into the inside.

The tar paper I refer to is that sticky stuff which usually has a foil backing.
I think someone else said there is a cheeper product called "roof patch" at the hardware stores.

Heres on example


The truth is you don't have to cover the whole pannel to stop the noise transfer. If the panel is say 24" by 24" like a door pannel. placing a patch of this about 5" X 10" sloppily in the middle will stop the reveb and transfer of sound.

The trick is to "not be semmetrical" A perfectly shaped piece placed carfully in the middle will only change what frequencies come through. An irregular shaped piece placed somewhere abouts the midle on a crooked angle will absorb and disrupt the sound transfer of just about all frequencies.

Thats the science used by the big three and many other vehicle manufacturues.

Find your self a piece of sheet metal like the metal shelving or something like that and do an expirement . wrap on it with your fist or pray water at it. Then attach a piece of sticky stuff to the under side and hit it again. Decide for your self how much is actually needed to deaden the sound.

Covering the whole pannel cost too much and wieghs too much and is a real prick if you have to remove it.

I will be doing my interior pannels as you are. insulation 1/2 the tickness of the wall cavity attached to the back of the pannels (except where the posts are) covered with a foil type backing. I will glue it to the pannels with spray on upholstery glue. The foil backing will also reflect sound.

M1D

m1dadio wrote:

The truth is you don't have to cover the whole pannel to stop the noise transfer. If the panel is say 24" by 24" like a door pannel. placing a patch of this about 5" X 10" sloppily in the middle will stop the reveb and transfer of sound.

The trick is to "not be semmetrical" A perfectly shaped piece placed carfully in the middle will only change what frequencies come through. An irregular shaped piece placed somewhere abouts the midle on a crooked angle will absorb and disrupt the sound transfer of just about all frequencies.

Thats the science used by the big three and many other vehicle manufacturues.

M1D

I've seen this example many many times at my work where I do autobody repair there. From many cars and vans where I would remove any inner cover panels or interior door panels - I would see this tar paper inside on back of any body panel. Most of times they're not on exact center of the panel there - and they are by smaller sizes ... oh, say like 1/4 or 1/3 of the size of the body panel.

I will get around doing this method on my van like the way above.

Thanks M1!! I'll look for that stuff.

i donot know if you will find the product you are describing ? just my thought is you may try a spray undercoating/ sound deadener and install the tarpaper while the spray is still wet??. on the house roor they use a ice & water sheild .it's 1 side you peel the paper off then install it under the shingle. it is very sticky it would also act like a sound deadener. just trying to throw some thoughts out there...

I used peel n stick roofing dry-in.I was still roofing at the time so the price was right help deaden sound in my pick-up cab very well.

actually some do use that thick spray undercoating and just spray patches of it on each pannel.

M1D

Grace makes a peal-n- stick product to wrap windows with. I think it comes in a roll 8" wide by like 50'. This way you don't spend $100 on a large roll of ice and water shield. I think Lowe's has it.

I was just about to get into my sound deadening and was looking at this product. http://www.fatmat.com/
I wasn't going to use it as an insulation though.I thought about backing it up with some of the foil backed stuff you by at Lowes.