In site situations where rain water penetrates into the stud cavity of the building envelope and concentrates at the bottom, the wet bottom plate becomes a moisture loading source. This moisture evaporates creating a vapor pressure profile that decreases with height and causes a corresponding absorption-evacuation mass profile through the sheathing. Such profiles were observed during an experiment designed to develop a test method to compare the relative performance of different wall configurations. In this experiment 31 wall assemblies were subjected to steady-state climatic loadings and uniform moisture loading consisting of water trays on load cells at the bottom plate within the stud cavities of the wall assemblies. In this paper, a new method is used to develop evacuation profiles due to evaporation of moisture sources in stud cavities of building envelope panels of various configurations. This method takes into account the vapor-pressure-vs.-height and vapor-mass-vs.-height profiles.