Rain infiltration mechanisms in ventilated facades: literature review, case studies, understanding common practice flaws

Ventilated facades are contemporary construction systems, which present a number of benefits in comparison to a traditional facade (unventilated or vented air cavity). Nevertheless, there is a gap in the understanding of its watertightness performance. It is commonly accepted by manufacturers and building practitioners as a rule of thumb that ventilated facade systems are designed to deflect the largest part of the rainwater that impinges on them and only a minimal part infiltrates through the open joints of the cladding. This residual amount of water is supposed to be drained at the bottom, temporarily stored in materials, or dry out to the interior, or to the exterior by means of the chimney effect inside the air cavity. In this way, the air gap of ventilated façades as well as being a capillary break for rainwater, acts as a channel for drainage of the infiltrated rainwater. However, some authors have already reported some pathological lesions on ventilated facades (stains and soiling damages due to biological colonization, problems with wind pressures due to the use of linear connections between panels and substructure, etc.) This paper presents a broad literature review on the response to rainwater of ventilated facades and typical pathologies. Next to that, an analysis of the main guidelines relating to the construction of ventilated facades is conducted. Finally, rainwater infiltration problems from real buildings with ventilated facade systems have been collected in a field study of 20 buildings. From this field study, four study-cases have been selected and thoroughly analysed, first measuring the components of the ventilated façade fixing system in order to draw their constructive detail, second working out on its water management and third, relating the water management to the damages observed in the visual inspections