Building walls are usually wetted during winter and dried during summer. This process can be treated as periodic process oscillated by annual cyclic input(temperature and humidity). This indicates the need of periodic steady state solution of the non-linear gorverning equations of this process. In this paper, it is studied that a numerical method of periodic steady state solution of the process which is governed by non-linear diffusible equations. In the periodic steady state solution, a initial state is equal to the state at the time after a period of main cycle. Based on the relations, a numerical method of periodic steady state solution is presented using the time variant linearlized equations derived the non-linear governing equations. Effectiveness of the solutions are discussed. Non-linear temperature and moisture behavior of the periodic steady state process in the wall are discussed, using Fourier analysis of solution. Closs effects between inputs frequency components are apparent.
