What is "rainscreen"

A rainscreen is an exterior wall detail where the siding (wall cladding) stands off from the moisture- resistant surface of an air barrier applied to the sheathing (sheeting) to create a capillary break and to allow drainage and evaporation. The rain screen is the siding itself but the term rainscreen implies a system of building. Ideally the rain screen prevents the wall air/moisture barrier on sheathing from getting wet. In some cases a rainscreen wall is called a pressure-equalized rainscreen wall where the ventilation openings are large enough for the air pressure to nearly equalize on both sides of the rain screen, but this name has been criticized as being redundant and is only useful to scientists and engineers.