Well that is interesting,not as much as I had guessed but EPS dose take water on.

I have used forms that come factory wrapped that sat out in the rain and you could really feel the difference between them and a dry one.

 This is why I know that an icf and water have issues. Water vapor will pass though it as well as the concrete from inside the house and hit the dew point on the outside of the wall up north here. When the water freezes it will expand and push the defis off the wall.
 Now do you see why I think you need a DRAIN SCREEN , or rain screen in the mix.
If air movement is allowed drying will happen faster.
 So think (OK I'll bet) you will be dry and at the same or even less weight than when you started. ( beer and  brats)
 We make eps with water (steam) so it is able to pass trough it by design.
 I still wonder if we did it in beer and used duck tape what would happen. ( a red green thing)

What dose foam desity realy have to do with it?

Water will do the same thing no mater what the density is (is it stiil made with steam)

May be it will do it faster but water will still be a problem to deal with a rain screen /drain screen (or am I all wet?)

The less dense panels have less eps per unit volume. Since the less dense panels have more air per volume, this air could be displaced with water. Just a guess,........only testing would tell. I wonder if forms that sit out in the elements with the rain, hot, cold, and a significant amount of time will have more moisture permeate into them. Might be psychological, but I have picked up forms that have been outside for a while, and I swear they were heavier than a new form. I also notice on hot sunny days when stacking a wall, you can hear the foam "poppping". I think this is the foam moving (sliding) over one another due to the heat,....who knows what this is doing to the foam at a molecular level.

Bunt

Now we got something here.

This is what I was getting at, The water will dry out if air and heat is allowed to remove it.

But if you put EFIS with out a rain screen or a drain screen on it and just reinforced it with fiberglass mesh so it wont fall off.

Where dose the water go?

 It can't evaporate so it travels into the foam deeper,and concrete and foam, and leaks into the home some were that you can't  even see that whats happening. This may even take 6 months for it to show up with out rain or water outside the home to explain what going on.
 This is my ? to you Am I all wet or dose this make sense.  I seen this and its all that I can come up with for what is happening.
Is it the EFIS problem  No it's not leaking right. 
 Well it may be just no letting the eps dry out from normal water vapor pushing its way out of the building.
 My short answer  to the original poster is not just vapor barrier but a place to drain the water behind the the barrier is needed.
Their is a block out their that this is built into and dose all of this if you pm me I will let you know what it is. No advertising here.
 I hope this helps
PS what about the beer and brat's or are we both right! COOL looks like a win / win

Jim,

From what I understand, once the stucco is wet/ saturated say after heavy rains, when the air temp/sun increases this will cause some of the water to migrate inward into the EPS foam; it may also keep the stucco from drying itself out more quickly.

I'm not a builder but I am trying to determine if this issue would be a problem in Florida, where heavy rain/humidity is prevalent.

This concept of drainage is also recommended by cement.org for ICF construction, although I undestand that the building codes themselves don't require it. 

Just think that is easier to plan for water intrusion and built accordingly than finding out later, perhaps years from now that the EPS foam or stucco exterior is failing due to the presence of wetting/water behind the stucco.

Thanks for your input and to anyone else who cares to chime in,

Mark P