Controlling humidity to prevent moisture and condensation phenomena is a growing problem for building designers nowadays. Ventilation and air conditioning are common solutions to avoid mold and condensation. However, to promote low cost energy buildings, an alternate solution may be to decrease the daily variation of humidity with anti fungi treated absorbing material. In this case, a very accurate evaluation of room humidity is necessary to determine material ability to buffer moisture. This paper briefly presents a model of moisture transfer between room air and walls for tropical climates. This model includes hygroscopic and nonhygroscopic wall behavior. The aim of the model is to calculate the water quantities buffered by walls and thus better evaluate room moisture. A validation of the model is presented consisting of a sensitivity analysis and an experimental comparison. The experiments carried out in a test cell are described. An application of the model is also proposed to tackle mold presence with various absorbing materials located in a tropical humid environment.