The importance of good seals in new buildings is noted when walls discolor because of water intrusion; when important papers are soiled, machines get wet and fail, floors and rugs are ruined. Then people think seriously about good sealing practices. Considering the problems and high financial impact that can occur, attention being paid to a good design in sealant joinery is growing.
One of the most reliable ways of eliminating water leakage through the sealant joinery in any building envelope is to apply the rain screen principle within the design, providing pressure equalization, thus preventing the vacuity of water through sealant expansion joints. The basic objective of the Two Staged Sealant System is to provide a major deterrent to water leakage at the outside face of the wall, and seal against air and vapor passage on the interior side of the air space, where the primary seal is exposed to little of the destructive elements of weather and sun.
A Rain Screen Joint Sealant System or Two Stage Sealant System refers to the function of the two beads of sealant as secondary and primary seals in the same joint; preventing water intrusion to the building through the sealed joinery. This system has proven to be an affective way of preventing the vacuity of destructive moisture into the building and its many components.
See full story at: http://uniproseal.com/2012/07/what-is-a-rain-screen-sealant-joint-system/