Recently, dwelling houses have become very airtight and nonhygroscopic. Accordingly, damages caused by vapor condensations has become real problems. An available countermeasure to treat the problem of vapor condensation is that to prevent condensation damage by utilizing hygroscopicity and capacity of moisture content in hygroscopic material. In order to examine this effectiveness, it is necessary to predict both temperature and humidity in a real dwelling house with hygroscopic material attached on walls. We made experiments in a full scale dwelling house under some condition of daily life. We verified adequacy of prediction by comparison of the experimental results with theoretical results. In conclusion, it was clarified that room temperature and humidity could be predicted in the experimental dwelling house with hygroscopic material attached on walls.