Drained and back-ventilated rainscreen cladding system (3)

Drained and back-ventilated rainscreen systems involve draining off most of the rain water at the outermost surface of the wall. Joints are designed to protect against the kinetic energy of wind-driven rain, either by incorporating baffles or limiting joint width. However, such claddings are not sealed, and no specific attempt is made to minimize leakage through the effects of gravity or wind by means of pressure equalization. Instead, the cladding is allowed to leak and the cavity behind the cladding is drained. Positive back ventilation is used to promote the rapid evaporation of any rainwater deposited on the inner leaf. Drained-and-ventilated systems are provided with ventilation openings in addition to drainage openings. This combination of openings allows air to circulate and dry the cavity between the inner and outer seals. In D and B-V systems the moisture barrier must be a water barrier. Its performance as an air barrier is less critical.