Air resistant - protects the wall assembly from air infiltration to increase the comfort of the building by reducing drafts and increasing energy efficiency. Water resistant - protects the wall assembly against water intrusion that gets behind the exterior cladding. Durability - has the ability to withstand the elements of the weather and tough jobsite conditions. UV Protected. Moisture vapor permeability - perserves the integrity of the wall assembly by allowing the moisture as vapor to escape to the outside.