Abstract: A wall panel structure for controlling humidity within a building having a panel assembly attachable to an inner wall surface of the building including: a first panel having a surface with a first predetermined porosity to moisture; and a second panel secured to said first panel with a space for accomodating airflow between the first and second panels, the second panel having a surface with a second predetermined porosity to moisture, the first perdetermined panel porosity being greater than the second predetermined porosity to thereby absorb moisture from air being circulated between the first and second panels; whereby humidity of an environment within the building is controllable.