My Insulation and Vapor Barrier

There are several threads about insulation and vapor barriers.  I'm not trying to be redundant but just want to share what I'm doing and I am not suggesting that this is right or wrong or that anyone should do it this way. 

I used Extruded Polystyrene Rigid Foam for two reasons:  1.  It is green, and safe.  2. It's the only thing locally that was 3/4" and I didn't want to drive over the mountain to get the pink stuff that I really wanted, also extruded but with a vapor barrier made on it

Extruded Polystyrene is a vapor retardant but not a true vapor barrier.   But I wet some scraps and the water beaded up and rolled off.  Extruded Polystyrene looks like it is put together in layers and is different from styrofoam like is used in styrofoam cups.

I bought plastic for a vapor barrier but after re-reading the threads here, I've decided not to use a vapor barrier.  I camp in the cold and I camp in the extreme heat.  Recalling the condensation experiments I did with my son, I don't think a vapor barrier would be much help and have concerns about it actually trapping the condensation (this is just my own thoughts, no real facts here.) 

The Polystyrene is very easy to work with but while flexible, it was too stiff to stay in the big bends.  I scored, it broke it in 4-6 inch sections and then taped it with foil duct tape on the back side and it rolled around the curve perfectly. 

It probably would stay without help, but I taped it in with the foil tape to secure it and it will also seal it. 

Here are a couple of previous discussions.

vintagetrailertalk.freeforums.net/thread/1146/moisture-barrier-placement-rib-design

vintagetrailertalk.freeforums.net/thread/428/vapor-barrier?page=1

vintagetrailertalk.freeforums.net/thread/749/vapor-barrier-inside-outside

Here is a link to the explanation of types of  rigid insulation:
vintagetrailertalk.freeforums.net/thread/1239/insulation-types-rigid-foam