AS THE NUMBER OF moisture-induced damages in buildings are increasing, demand is increasing for calculation methods in building engineering to assess the moisture behavior of building components. Current events, such as moisture-originated failures of wood frame construction in low-rise residential buildings, increased heat losses due to the presence of wet insulation materials, the heat pump effect due to evaporation condensation cycling, measures taken for the preservation of historical buildings, or retrofitting insulation in existing buildings, are closely related to the moisture performance of the building structure. However, solutions to moisture-induced problems may be difficult when several interacting mechanisms of moisture transport are present.