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I'm just getting started with my 2012 Chevy Express 1500 cargo van. No windows in cargo area except rear. I've read a good deal here on the forums but still have questions. I don't want to overthink this too much, but don't want to run into unforeseen problems later on. For the walls and ceiling, the friend that's helping me suggested we go, in order from van skin in, pink rigid foam insulation, plastic sheeting (vapor barrier) and then my choice of plywood paneling.  I'm reading a lot about using 1/2"polyiso rather than the rigid foam board. Why is it favored? Is the plastic sheeting a viable barrier?
We do have plans to use polyiso under the plywood on the floor albeit thicker. I plan to try to stay within moderate temps, but as weather's unpredictable, I'm sure there will be times that it will be cooler or warmer than desired. I know I can dress warmer/cooler and I do have two fantastic fan vents already installed.Thanks in advance!
If I missed a post regarding the above feel free to redirect me.
I'm just wrapping up on my 2nd conversion, here are my thoughts:

1- Rigid foam board. I've used this a lot and like it. It's just a little behind polyiso in terms of R-value per inch, but also cheaper. I use it everywhere but the ceiling, and that's where I use Polyiso. The reason for this is that polyiso stands up to high temperature much much better than EPS foam board, which becomes very very soft at around 160 degrees F - a temperature that can be approachable on the roof under the right conditions (hot, sunny climate, dark colored roof, etc). If I had to guess, the hottest I've seen on the ceiling of either van may have only been about 120 degrees, but I'm not in a very hot climate and I have a white roof with solar.

2- Vapor Barrier. I would strongly advise against it! The metal walls of the van are already a vapor barrier! Adding another vapor barrier will likely do more harm than good, trapping any moisture that infiltrates its way in between the two. Additionally, once moisture gets in there, it will have that much harder of a time getting out! Ventilation is where you will want to focus your energy when it comes to moisture control in the van

3- In both conversions that I've done, I went simple and light on the floor! I simply covered the (stripped down) floor with those 2' square interlocking puzzle mats, followed by a layer of 1/4" underlayment then applied laminate flooring over top. The resulting floor is thin (1"), very light (90 lbs complete) and plenty strong. If you check out my build log I show it in pretty good detail.

Good luck!
Listen to Viavacavi, he's giving you great advice! Mine is very similiar

1) Polyiso is better but pink board is very good.
2) No vapor barrier
3) Throw down area rugs on the floor and call it good. Insulation on the floor is a waste and why give up all that headroom?
Bob
Thanks for the input!  Looks like I'll skip the vapor barrier.
I do have a question regarding polyiso.  I thinking of adding one inch polyiso under a 1/4" or 1/2 " plywood and adding a polyurathane coating and call it good. If it factors in, I'm only about 120 lbs, and the actual floor area after adding the bed and storage won't be very big, about 4 x4 or so. The question is, the only polyiso I've found is 1/2" or 3/4".  Would it be acceptable to do two of the 1/2" to get the 1"? Any reason not to stack them?
Thanks again!
(09-08-2016, 05:14 PM)LookinUp Wrote: [ -> ]The question is, the only polyiso I've found is 1/2" or 3/4".  Would it be acceptable to do two of the 1/2" to get the 1"? Any reason not to stack them?
Thanks again!
There is no reason not to stack the polyiso...it works fine.

Use the 1/2" but stagger the seams so that no seam is on top of the other.

Most people use the 1/2" so that it's thin enough to bend without cracking on the contours of the inside of a van.
Almost There is correct. I want to add the plywood doesn't need to be 1/4" or 1/2" unless you are going to anchor things to the plywood, 1/8" is just fine. much lighter and much easier to work with. highdesertranger
In my old Chevy build, I kept the black mat chevy puts in the back of the cargo vans with the jute pad underneath. Then threw down a few area rugs like Bob mentions. Easy to clean and sweep, no added weight. Already did a fine job of deadening sound and I saw no reason to reinvent the wheel for the floor area which is covered 80% by the time the build is done.
Thanks, actually I will be anchoring things to the floor such as the bed, a table over my fridge and the cabinets. Some of which will also be attached to the walls.