GCP Applied Technologies PERM-A-BARRIER VPL 50 Membrane is a fluid applied, one component, STPE vapor permeable air and water barrier. When applied to approved construction surfaces PERM-A-BARRIER VPL 50 liquid is designed to cure and form a resilient, monolithic, fully bonded elastomeric sheet and to create a continuous barrier against air infiltration and exfiltration, reducing associated energy loss and condensation problems. PERM-A-BARRIER VPL 50 Membrane is specifically designed to provide superior protection against the damaging effects of air and liquid water ingress on the building envelope. Vapor permeability allows the wall to breathe and dry by preventing water vapor from being permanently trapped and condensing within the wall. While PERM-A-BARRIER VPL 50 Membrane is vapor permeable, it is impermeable to liquid water, allowing the material to act as a water drainage plain within the wall.