The Moisture Transport in Building Materials (mt) interface () is used to model moisture transport in building materials by taking into account moisture storage, liquid transport by capillary suction forces, and the diffusive transport of vapor. A Building Material model is active by default on all domains.

When this physics interface is added, these default nodes are added to the Model Builder: Building Material, Insulation (the default boundary condition), and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Moisture Transport in Building Materials to select physics features from the context menu.

The shape functions used for the relative humidity are Quadratic Lagrange.