Is usually defined “waterproofing” the ability of a window to prevent the infiltration of water even in the case where between an external environment and the internal rainy there is a pressure difference (strong wind). This test must be performed on the product that has been tested in wind load, which must demonstrate that such tests do not have decreased the ability of resistance to the infiltration of water. Also in this case there is a standardized test procedure: the frame is subjected to progressive pressure, ie to playback the thrust of the wind, toward which is also splash water to volume and constant pressure. Consequently, in relation to the pressure value reached just before the occurrence of water infiltration, is assigned the class performance, according to UNI EN 12208, which provides up to nine classes (also depending on the type of exposure of the product): 1, 2, 3, 4, 5, 6, 7, 8, 9 (method A - method B).