A method of making a non-woven fibrous media, combining high vapor permeability and low liquid permeability, includes the steps of providing a non-woven fabric formed from fibers that are prematurely crystallized during fabric formation and have a wide heat of fusion range distribution, and calendering the fabric to soften the small polymer crystals therein of low heats of fusion, but not the relatively larger polymer crystals therein of relatively higher heats of fusion, thereby to retain high vapor permeability while providing low liquid permeability. The polymer is preferably isotactic polypropylene.