Insulation Question/Need Help

[John61CT]

> Is this the stuff that everyone told me not to use because it would cause the van sides to bulge out? (I’m only planning to use it on gaps where it is free to expand inward without resistance and so should put no pressure on the van wall.

No problem as long as you know and you're careful, little at a time.

Spray can do the same, need to drill escape holes pretty frequently in an enclosed space.

Done right, then it's just wasteful if you use too much at once. And major mess, no solvent cleans it up once cured (20-90 sec), have to scrape / sand it off.

 

[John61CT]

> The ribs are like 2” into the vehicle envelope. Filling the large gaps with insulation is fine, but am wondering how to isolate the ribs (which have a direct thermal connection to the outside van wall.). I can fill them with insulation, and thermally isolate them from the interior structures, and I guess I can give up an inch in that process and fill it with insulation.

Yes just spray more layers in between the ribs until you're more or less flush with the ribs, trying to follow the same curve. Fill the ribs or not your call.

Then 1-2 more layers, covering all exposed steel IMO at least an inch, but depends how much living space you're willing to give up.

Sawing/scraping to get a nice even facing surface is a real PITA. Rather than just airspace where uneven, you could fix your vapor barrier and innermost luan? lining in say 8-16" course from the bottom up, squirting or pouring in the last layer of foam as you go to maximize R-value.

> Can you tell me what you mean by “6 mil dropcloth” for a vapor barrier? Is that just the plastic sheet you commonly see for covering a floor while painting? How about Tyvek? Is it a better vapor barrier?

Yes, plain plastic, thicker if you're concerned about it getting ripped or punctured. I'm usually skeptical of "breathable" claims, since blocking all air infiltration (convection heat loss)

but in this case the complete foam envelope is already pretty complete.

Then again better for any offgassing vapors to only go out not in right?


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[SoulRaven]

Is this the stuff that everyone told me not to use because it would cause the van sides to bulge out? 

The "pour" 2 part foam, would likely only bulge out if it were used within a tightly enclosed area, as was stated several times both on their website and here as well. That "bulging" is really not a concern, as my van's walls are open and using closed cell DOW 2 part "spray" foam is still an option & for now, an uncommitted choice until I do decide, but not until after discussing with DOW FS techs. 

I have decided to not use the "Pour" 2 part foam. I prefer the DOW 2 part Spray Foam.

It is fairly obvious to not use that type of foam within a van's support vertical ridge beams, or within already enclosed walls. I will update, after I discuss the OTHER "Spray 2 part Foam" with DOW tech support on Monday, that is, if they are available to talk.

 

[Canine]

Buying insulation from roofing companies is often cheaper. They are also more likely to have the heavy duty stuff. (If rigid foam insulation can be referred to as 'heavy duty'. lol) Keep in mind they stock for themselves or for wholesale to contractors; they don't cater to the general public. However, if you go in there cash or credit card in hand with a specific list of what you want and a way to easily load and haul it off right away, they will more likely sell you several sheets. If you go in there asking, "Should I use XPS or polyiso?" or if you make several trips getting only a few sheets at a time, that will turn them off in a hurry. I saved hundreds when I brought my truck in, had my list in hand, and loaded up. And I mean loaded up. It didn't seem like much, but when it was piled up in one stack, it was a lot!

 

[SoulRaven]

^ Good ideas. I would never have thought to go to roofing co nor could I 2nd guess their ways of business vs general public dealings. Thank you Canine!