GreenGuard® RainDrop® approaches the area of moisture management in two ways. First, as a barrier, it has typical housewrap moisture and air penetration resistance. But, it is unique in that it also is designed as a drainage plane. When siding is installed over GreenGuard® RainDrop® , channels remain for water to drain away from the surface and, with the water gone the surface moisture dissipates through normal drying by evaporation. In addition, GreenGuard® RainDrop® breathes to allow moisture vapor to escape from the wall cavity.