Cool
There are many on the market that claim this, but none do. Most have a vent system combined with some kind of inner mesh. The idea here being to let the sweat out of the open vents. In reality I have never worn a waterproof jacket that doest get me soaked inside in my own sweat. Often they simply serve to keep one warm, rather than completly dry. So I only wear a waterproof jacket in the cold. It would be good to be able to wear a waterproof in a summer downpour as well for example.
To my mind this isnt about using exisiting materials, its about finding a new type of material altogehter...
something that is pourous one way but not the other...jmho.
Im pretty sure the big manufactures would be on this if they knew how.
Dont forget ..that jacket needs to be aerodynamic, wind proof, have all the right fastenings, reflector strips, be easily packable down to a very small size, and washable, as well as C H E AP!!