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

Reliability and adequacy of current watertightness test standards used to evaluate the performance of façades

Watertightness test standards are used to evaluate enclosure components in terms of water penetration resistance. Currently, there is a wide variety of watertightness tests in use for façades elements and wall systems. However, recent research has revealed many inconsistencies in the possibility of current test standards to reproduce real exposure conditions. As such, the main test parameters specified in watertightness test standards have been called into question. Nonetheless, these studies do not pay attention to the protocols and the technical specifications incorporated in the test standards. Neither to the influence that these aspects could have on the watertightness results. The present paper provides a general overview of current watertightness tests standards from around the world. Thereafter, a thorough comparison of the technical specifications incorporated in the protocols of the test standards has been carried out. Finally, an evaluation and discussion of some parameters suggested in the tests standards is undertaken based on the state of the art and laboratory experiments over diverse mock-ups