Field tests to study the pressure equalization on air permeable façade elements

The net wind load on the outer layer of a façade consisting of multiple layers is determined by the external pressure and the cavity pressure. For an air-permeable outer layer, the cavity pressure is dependent on the extent to which the external pressure equalizes over the openings. Minimizing the pressure difference between external pressure and cavity pressure has beneficial effects with respect to the amount of fasteners needed for the elements, thus saving material and avoiding unnecessary penetrations of the thermal insulation layer. Current rules to determine the loads on such structures are very crude and conservative, and are based on very little experimental evidence. A full scale experiment has been set up on a 158 m high tower in Rotterdam, the Netherlands, in order to study pressure equalization in a ventilated cavity. The main interest of this study is the net wind load on the outer layer of the façade. The first results show that pressure equalization occurs very fast and that the cavity pressures generally follow the external pressures rather well