Cup method based on the EN ISO 12572 is the widely used method to measure the water vapor permeability in porous building materials. The cup test is categorized into two ranges: dry and wet conditions. This technique evaluates the vapor pressure gradient across the sample, and the entire cup is assessed by monitoring its weight over time. While the external environment is precisely regulated by climate chamber, appropriate solid desiccants or saturated salt solutions are used to control the interior of cup. Dynamic vapor sorption (DVS) method provides distinct advantages because of the highly reproducible data over the wide range of the relative humidity as a function of time. DVS method was utilized to measure sorption hysteresis and equilibrium water content and kinetic of sorption. In this paper, we applied the macroscopic model to analyze the dynamic vapor sorption in an earthen brick with taking into account the sorption hysteresis. The effective water vapor permeability calculated by the optimization method in our model and compared against the standard cup method test according to EN ISO 12572. The results showed that applied model is able to predict the water vapor permeability of earthen brick as a function of the relative humidity and as well as the resistance factor. The error in the simulation results was below 10% within the relative humidity in the range of 20% and 95%.