Experimental assessment of rainwater management of a ventilated façade

Façades are not watertight systems in which the exterior surface of the cladding plays the role of the water shedding surface; the air space is the drainage plane; the exterior surface of the thermal insulation layer acts as water-resistive barrier, and the interior layer of the inner leaf is supposed to be the air barrier. The degree of watertightness of ventilated façades relies on the characteristics of the materials used, the geometry of the external cladding element, and edge profile of the joints. Hence, in this article, we extrapolate the laboratory testing to develop a holistic approach on the water management of ventilated façades. The laboratory test showed that 50% of the water deposited to the surface of the wall splashes back, 22% creates a runoff film along the exterior surface of the cladding, 27% infiltrates into the cavity behind the cladding, and <1% reaches the inner layer of the wall. Given these results, the moisture load has been determined for a range of wind-driven rain loads and vertical joint configurations. Such information can be used as input to hygrothermal simulations.