Assessment of enclosing structure unsteady-state moisture behavior using moisture potential theory

The logistics of the moisture movement in the building wall is very important. We need to know the movement of moisture from one point to another. Two known moisture transport equations are analyzed. The first one is based on vapor-state moisture movement in sorption wetting zone, and the second one - on combined transfer of vapor and liquid moisture. Their strengths and shortcomings are described. Analytical formula for moisture potential F developed by V.G. Gagarin and V.V. Kozlov is given. This formula allows taking into account moisture transport simultaneously in sorption and ultrasorption wetting zones in a consistent way. Derivation of a new moisture transfer equation based on moisture potential F is given. Benefits of such approach are introduced. Boundary conditions for moisture transport problem are formulated, problem solution by finite difference method using an explicit difference scheme is given. The proposed method is applied to single-layer enclosing structure made of aerated concrete blocks. It is demonstrated that illustrated method takes into account wetting inertia, and allows moisture distribution determination in all enclosing structure sections at any time. Results can be presented as moisture distribution along enclosing structure thickness, or as enclosing structure average moisture variation during a year. It is highlighted that calculation using the proposed method does not require values of separate moisture transfer potentials.