US Patent 7117649 Vented furring strip

A wall system for a structure including elongate furring strips having a multiplicity of transversely oriented air passages. The elongate furring strips are arranged on a first envelope layer of a wall and covered with a second envelope layer. The furring strips space the first and second envelope layers apart, forming a plurality of enclosed cavities or air spaces. The cavities are in fluid communication with each other through the air passages in the furring strips, and may be in fluid communication with the outside atmosphere. Air is thusly enabled to circulate from the outdoors through substantially all portions of the cavities, promoting drying of the first and second envelope layers, which may be sheathing and finish siding.