One of the most significant changes to the design of EIFS in the last few decades is the advent of EIFS with drainage. EIFS with drainage has a cavity behind the foam through which water in that area can migrate downward and out of the wall. EIFS with drainage also have a weather resistive barrier on the substrate side of the cavity. The WRB's function is to protect the substrate from water and keep water out of the wall structure. Sometimes, WRBs are used in conjunction with a barrier-type EIFS without an adjacent drainage cavity, simply to protect the substrate.
Work is taking place now in various technical organizations to qualify WRBs: In other words, to define what properties make for one that will function properly. This month's column is an explanation of some of the key properties of WRBs.