The study estimated indoor thermal environment of the traditional building in summer and winter terms were simulated with CFD analysis. Furthermore, As a results, We could quantitatively show the usefulness of passive technology by conducting numerical fluid analysis for buildings from the past to the present age. By comparing various models against one building, it is important to confirm that spatial confirmation that the passive technology applied to traditional Japanese buildings contributes greatly to the fittings applied inside done. In addition, by verifying the reproducibility of past thermal and air environments using numerical fluid dynamics, it is possible to compare models of traditional buildings that have been carried out in past studies so far, by using a credible model of passive technology I was able to clarify the usefulness. It is thought that the result of this time will be useful for the improvement of the basic data on preservation utilization of the mulberry house currently being preserved.