Pressure-equalized rain screen systems function by blocking all of the forces that can drive water across a barrier. See the article on Moisture Protection for a complete explanation of how pressure-equalization resists water passage. As related to curtain wall systems, PE rain screen systems design the inside face of glass and the inside face of the glazing pocket and the interconnecting gasket or wet seal as an airtight barrier. The outside face of glass, exterior glazing materials and the outer exposed face of aluminum framing function as a rain screen, shedding water away. Between the exterior rain screen and the interior air barrier a pressure-equalization chamber is formed in the glazing pocket, which serves to reduce water penetration by eliminating (equalizing) the pressure difference across the rain screen that tends to force water into the system. Minor amounts of water that may penetrate the system are weeped harmlessly to the exterior.
Water-managed systems appear similar at first glance, incorporating drains and weeps from the glazing pocket, but no effort is made to create an air barrier or "zone-glaze" each glass or spandrel unit, and therefore a larger amount of water is forced into the system and must be weeped away. Also, since no air barrier exists, the pressure differential between the glazing pocket and the interior may be strong enough to force water vertically higher than interior gaskets, resulting in leaks. Weep holes in a water-managed system function largely to drain water that enters the glazing pocket while weep holes in a pressure-equalized system function primarily as vents to allow air movement between the exterior and glazing pocket. Weeping of water is only a secondary function. Note that the easiest way to recognize a pressure-equalized rain screen system is yo note that the that glazing pocket around each individual unit of glass is isolated air tight from adjacent units, most obviously with plugs or seals at the gaps between screw splines at mullion intersections. Detailing of spandrels, shadow boxes and interface with adjacent construction must maintain the continuity of the air barrier and rainscreen to function properly with a pressure-equalized rainscreen curtain wall framing system.
Material : corten steel