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Old 07-11-2014, 11:45 AM   #1
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Default Spray foam

Why would you fool with dynamat or some other similar product, when you could just spray foam?

Look at the depth of these ribs! Lots of room for foam insulation, yet there is none in my van that I can tell.



I think it would save alot in labor.
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Old 07-11-2014, 01:21 PM   #2
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Default Re: Spray foam

I am generally a bit Leary about spray foam products because there are more sham products on the market than legit. Over the course of my architectural career I had researched and had independently tested just about everything on the market. I had that luxury with a company building billions of dollars of new construction yearly. The only products that performed to claims were the polyurethane/polyisocyanurate closed cell products. They are generally expensive, you might have issues with blowing agents, odors and combustibility. In buildings and homes Sheetrock covering was a requirement and that isn't going to happen in an RV at least in a B. Read the claims carefully by spray foam companies. They are generally well written evasive non-answers that would make a politician proud. Oddly these companies survive and RV builders even use the products which in turn seems to make them legit. Spray foams just intuitively seem like they might work but surprisingly dead air could work better than many of them.
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Old 07-11-2014, 02:08 PM   #3
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Default Re: Spray foam

In home, I have spray foam insulation - couldn't be happier with it. I keep cool 3800 sq ft for around $150 a month. It's exposed in the attic - you can actuallly stand up there and it's as cool as the rest of the house. It's also exposed underneath the house in the crawlspace. Whether any of this violates code, or the manufacturer's requirements, I don't know.

The ambulance video I posted showed them applying aluminum sheeting over the foam. I suppose they are figuring that provides the fire protection requirement.

Another benefit, I would think, is that once your electrical and plumbing was installed in the walls, and then you spray, those items are locked into place. That could be a detriment in some views, but it certainly would prevent movement and chaffing in most cases I would think.

For sound deadening, I don't see how you'd do better than foam.

I may be able to pry off one of my van's plastic side panels and see what's in there. I'll post a pic if I do.
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Old 07-11-2014, 10:52 PM   #4
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Default Re: Spray foam

I don't know if it is true but I was once told that spray foam may emit some type of gas like formaldehyde or something. Possibly earlier products may have, but I hope that it would be safe to use in a closed environment. Could someone clearly if this is true? I hesitated to use it in a closed area because of this reason.
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Old 07-12-2014, 12:17 AM   #5
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Default Re: Spray foam

There was once a product known generically as UFFI - urea formaldehyde foam insulation. It was used for a number of years in home insulation. Eventually (years ago) its use was discontinued (banned?) at least in Canada. Its potential health effects were such that a homeowner selling his/her home had to declare the home was UFFI free.
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Old 07-12-2014, 12:34 AM   #6
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I've mentioned this in other forums... The research i found on moving vehicle application of spray foam products available back in 2010 showed that after a couple years of daily driving the foam had disintegrated to clumps and dust behind the RV's walls. I think you will find that no DIY'er who has done thorough due-diligence on the subject ever installed the product(s). They went the matt/board/wrap way (as we did in our conversion).

Thom

PS...the other reason is proper air flow and ability for condensation to exit down the inside surface of van's exterior wall. If you look closely at a vehicle's walls you will notice periodic "weep holes" to allow any moisture/condensation buildup to exit and not cause rust. Case in point; there was a DIY'er at another forum who had a professional spray foam the interior of his van conversion shell. On the third or fourth year he had to remove part of a lower wall for some reason...that is when he saw the clumps/dust and rust. Any water from condensation had been trapped and had caused quite a bit of damage from what i recall.
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Old 07-12-2014, 12:52 PM   #7
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Default Re: Spray foam

not sure if sticking dynamat all over would be any different as far as condensation goes. I'd think that the more insulation you have, the less risk of condensation you'd have.

Now if you spring a leak in the vehicle skin goes, that kind of water needs to go somewhere.
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Old 07-12-2014, 01:04 PM   #8
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Default Re: Spray foam

Quote:
Originally Posted by wincrasher
not sure if sticking dynamat all over would be any different as far as condensation goes. I'd think that the more insulation you have, the less risk of condensation you'd have.

Now if you spring a leak in the vehicle skin goes, that kind of water needs to go somewhere.
I can't speak to how well the foam holds up in a van sidewall, but the foam that Roadtrek used to seal some of the openings under the van that go to the interior has held up OK for the 6 years of our C190Ps life.

I do know that using any kind of insulation that will absorb and hold water is not a particularly good idea. It doesn't matter if the water comes from leaks or condensation, it the insulation gets and stays wet, you will have rust or mold issues. Although not the worst, even fiberglass batts will hold moisture, and many of the sheet stuff that is made for under floor mats, or in doors, is terrible for holding water and rusting floors or other area. Heavy type absorbent stuff like mineral wool, cellulose, maybe even the denim stuff (I have never seen it in person) can hold a lot of water and vapor barriers just keep them from drying as quickly as they would without. I really don't think you can use a vapor barrier that would keep all moisture from getting from inside the van to the metal skin as there are just too many paths to get there, and if it gets there it will condense if it is cool outside. If you get moisture on your single pane van windows, you will also have moisture even sooner on the metal skin.
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Old 07-13-2014, 01:19 PM   #9
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This is interesting - check out post #15 on this link - http://www.promasterforum.com/forum/...t=16609&page=2

They are spraying with a ceramic coating first and then using batt. I imagine you still have the problem of not plugging any drain holes, but it is an interesting approach.
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Old 07-13-2014, 10:24 PM   #10
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Ceramic paints are the too good to be true Holy Grail dream. I feel about the same as this guy. Ceramic Paint-on Insulation: Does it Work? A few mills thick is not insulation. I'll spend money on it like that author when water-powerd Class Bs become a reality.

Vapor barriers are tricky. Basically vapor will flow from inside (heat) to outside in cold weather. Vapor in insulation will condense when it hits it's dewpoint inside a wall. That is why you place a vapor barrier inside. Outside the steel is a perfect vapor barrier. inside is more difficult. In homes a plastic poly wrap is about as good as you can use behind sheetrock but it gets punctured. It retards but is not perfect. About the best you can do in a B is to use the Dynamat or HushMat products which have an aluminum foil backing (aluminum foil another near perfect vapor barrier) with foil back tape. They are not insulation as their primary function is for sound but they can be effective heat loss or heat gain barriers as well from air infiltration or exfiltration. Then in some climates, especially hot humid climates you do not want a vapor barrier at all because you want the vapor just to pass through completely and probably never reach a dewpoint to condense. Vapor will get in and will condense which is why the bleed holes. So what do you do with a B that goes everywhere and already has steel on the outside?

I mentioned earlier the only good foam is a closed cell foam and they need a chemical blowing agent to place. After curing it is all the locked closed cells that create the insulation qualities. It is the chemical blowing agents that have been a problem in the past but I think now they have been eliminated in the building industry products.

I am amazed that companies can claim their blowing agent can be water-based and also not be closed cell. That means if originally mixed with water to blow, it can readily absorb water again. In effect we tested them and they disintegrated with moisture. Read their claims carefully. Note they will cite an insulation testing standard and you'll assume they actually tested their products. To a T we asked every company to provide an independent testing report on their products and not one actually had one. They assumed since their product was foam it was good to go without testing. So we tested them.

Stuffed insulation products like cellulose, mineral wool, fiber glass and that blue denim are all chemically treated or inert so that the material itself will not absorb moisture.

My knowledge really ended 7 years ago when I retired and shoveled out all the stuff in my brain I hoped to have to never use again. So, if there have been new developments since, I haven't kept up. But it is really simple physics. I did develop an almost true rule at the time of research. If the foam was white it was worthless because most all the bogus claimants had white foam. But just about anything will work as long as it stays dry and doesn't lose its integrity. That is why they stuffed crumpled up newspapers in walls a lot before WWII and made remodeling old homes fascinating finds. Newspapers of old evidently had integrity. Water blown foam has the integrity of the RV recommended toilet paper you put in your toilet. Think about that.
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