Computer-simulation study on fire behaviour in the ventilated cavity of ventilated facade systems

Fire spread through the facades is widely recognized as one of the fastest pathways of fire spreading in the buildings. Fire may spread through the facade in different ways depending on the type of facade system and on the elements and materials from which it is constructed. Ventilated facades are multilayer systems whose main feature is the creation of an air chamber of circulating air between the original building wall and the external cladding. The "chimney effect" in the air cavity is a mechanism that improves the facade's thermal behaviour and avoids the appearance of moisture from rain or condensation. However, in a event of fire, it may contribute to the quickest spreading of fire, representing a significant risk to the upper floors of a building. This study deals with some aspects of fire propagation through the ventilated cavity in ventilated facade systems. Also we review the provisions stipulated by the Spanish building code (Codigo Tecnico de la Edificacion, CTE) [1] to avoid fire spread outside the building. The results highlight the importance of the use of proper fire barriers to ensure the compartmentalization of the ventilated cavity, as well as the use of non-combustible thermal insulation materials, among others. In addition, based on the results, it might be considered that the measures stipulated by the CTE are insufficient to limit the risks associated with this kind of facades systems. The study has been performed using field models of computational fluid-dynamics. In particular, the Fire Dynamics Simulator (FDS) software has been used to numerically solve the mathematical integration models.