The rainscreen principle theorizes that the equilibrium of air pressure between the outside and inside of the "rainscreen" prevents water penetration into the building itself.

The majority of the water is deflected off the outside face of the cladding panel. Any water that may have penetrated during the rain fall is removed by drainage. As the rainscreen system is pressurized and the joints are slightly open, pressure equalization in wind blown driving rain is immediate. Pressure inside the internal void is equal to the pressure outside; therefore, rain does not have a tendency to enter the cavity.