Watertightness and water management of curtain walls

Curtain wall systems typically rely on pressure equalization to achieve a good watertightness. The insulating glass unit is clamped to the mullion between two gaskets, functioning as a rain screen and airtightness layer. When the curtain wall system is subjected to wind driven rain and a pressure difference, water may penetrate past the first gasket into the drained cavity. Depending on the airtightness of the interior and exterior gaskets, the pressure equalisation will determine the actual pressure over the exterior gasket. That pressure, in combination with hydrostatic pressure from water runoff, is the most important driving forces for water ingress. In this paper, the watertightness and drainage of water in curtain wall systems is investigated. In an experimental setup, a fullscale curtain wall system was subjected to a range of pressure differences under static and cyclic test procedures. For each condition, the water ingress into the drained cavity was measured. Next to that, the phenomenology of water ingress was analyzed based on airtightness measurements, dynamic watertightness tests, and pressure equalisation.