If I remember correctly, the CFM ratings for windstopper and eVENT lies between 0,3 and 1 CFM.
I have no idea where you're getting this info, but every source I have says otherwise. These materials do not rely on air permeability for their breathability. Schoeller's WB-400 was designed for softshell stretch wovens and relies on it's small amount of air permeability for it's breathability. In fact, what makes this Schoeller material unique is that it has a slight bit of cfm something that no other membrane has been able to accomplish. The only thing close would be Polartec WindPro which it's cfm is around 20 or so.
I stand by what I said and have not doubts. I'm certain that eVENT is completely windproof recording 0 cfm. I will have to respectfully disagree.
By the way, WB-400 is similar to Windstopper in that both are a laminate. The difference, again, is that WB-400 has a slight bit of air permeability where Windstopper has none.
Not much but enough to have an effect on breathability (it is the reason why eVENT performs that well) and why you can feel a slight breeze through the fabrics
The reason why eVENT performs well is not because of air permeability. eVENT does well because it doesn't have a solid PU membrane blocking the moisture from escaping. It has nothing to do with how much air can pass through. The pores are simply too small. A way of demonstrating this is to take a piece of eVENT or Windstopper and try to blow through it. I've done this countless times in demos and have never felt a thing. If eVENT allowed a slight breeze to pass I should be able to feel my breath which I don't.
eVENT works slowly through a pressure build-up inside the jacket forcing the moisture through the membrane. Goretex relys on the PU membrane to absorb moisture once it's built up, thus the diffusion principle when mated with a hydrophilic material.
I would also dispute that the 1st generation Gore was more breathable than eVENT. I would say they had similar characteristics, but I doubt one was better than the other in this regard. Again, why Gore has floundered with it's technology when they owned it for so long is beyond me. For many, it's hard to believe that they are relegated to take a back seat to another w/b brand. I think their intro of ProShell is an indication that they are floundering.
Why do people say this about eVENT and not about windstopper ? It could be because windstopper garments in general seem to use heavier face fabrics and linings which have an effect too.
With all due respect, this statement doesn't really make much sense. If Windstopper has the same ePTFE characteristics as eVENT, they they should perform similarly. Windstopper is typically either laminated to stretch woven material in a softshell application or to 100 weight fleece. Both these materials are the worst at stopping wind. On the other hand, eVENT is typically laminated to tightly knit outer material that is much better at keeping wind at bay. In fact, most of the outer material that eVENT uses has a very high thread count per square inch. So by my deductions, the eVENT material would perform much better than Windstopper in stopping wind.