This node adds an initial value for the relative humidity that can serve as an initial condition for a transient simulation or as an initial guess for a nonlinear solver. In addition to the default Initial Values node always present in the interface, you can add more Initial Values nodes if needed.

For User defined, enter a value or expression for the initial value of the Relative humidity . The default value is 0.5. Else, select an Ambient relative humidity defined in an Ambient Thermal Properties node under Definitions.

Physics Tab with interface as Moisture Transport in Air or Moisture Transport in Building Materials selected:
Domains>Initial Values