To become more energy efficient, structures are now being built with extreme airtightness.
This is why air and water barriers are becoming increasingly important. Tighter buildings are designed to prevent outside air and bulk liquid from entering, while allowing damaging interior moisture vapor to escape.
Building wraps are often used even though they are easily damaged. This is primarily caused by the difficulty of properly installing building wrap; every staple hole, seam or wall intrusion allows for movement of air. Uncontrolled air movement can lead to unwanted condensation due to temperature differentials across the wall.