The term "open-joint ventilated facades" refers to a building system in which coating material (metallic, ceramic, stone or composite) is hanged by means of a metallic-frame structure to the exterior face of the wall, creating an air cavity between wall and slabs. The coating material is placed in an arrangement of slabs and a series of thin joints from slab to slab to allow the surrounding air to enter and leave the cavity all along the wall. In addition to aesthetic and constructive reasons, the main interest in open joint ventilated facades is their ability to reduce cooling thermal loads. This is achieved by the buoyancy effect induced by solar radiation inside the ventilated cavity, where the air can enter or leave freely through the joints. This paper focuses on the phenomena produced on a typical open joint ventilated facade, and the comparison of its energy performance with that of a conventional sealed air cavity facade. The thermo fluid-dynamic behaviour of both systems has been analysed with CFD techniques and the results of the 3D simulations conclude that open-joint ventilated facades can help to achieve important energy savings in climates with hot summers and mild winters. (C) 2011 Elsevier Ltd. All rights reserved.