PERM-A-BARRIER® VPO is a fluid applied, one component, acrylic membrane that provides continuous air tightness and water protection throughout the wall assembly. PERM-A-BARRIER® VPO is dark-colored and designed for exposure to indirect and intermittent sunlight, such as behind open joint rain screen systems. PERM-A-BARRIER® VPO is for wall assemblies requiring “breathable” characteristics. As a vapor permeable membrane, PERM-A-BARRIER® VPO permits the transfusion of water vapor that may otherwise condense in the wall structure; but is impermeable to liquid water, which allows the material to act as a water drainage plain. The Volatile Organic Compound (VOC) content of PERM-A-BARRIER® VPO is less than 20 g/L.