Quantification of Ventilated Façade Effect Due to Convection in Buildings

Abstract

[EN] The external layer in a building has a paramount role under the building s energy behaviour point of view. The ventilated façade is a passive system installed on buildings to improve the global energy behaviour. The ventilated façade performance is described. Ventilated façade is mainly based on convection and radiation. This contribution focuses on the convective effect due to buoyancy driven respect to wind forces in the ventilated gap and their influence on the building thermal behaviour. To do so, several computational fluid dynamics models are undertaken with 1.5m/s, 0.5m/s and 0.2m/s wind velocities and a wind temperature of 298K and 300K. In the modelled conditions, the temperature of the external face of the façade was decreased due to the ventilated façade effect at 0.2m/s. 35% of the temperature reduction was due to natural convection buoyancy-driven effect and the rest due to wind-driven effect. With higher wind velocities (1.5m/s) the temperature reduction due to the convective effect was negligible. According to these simple trials, it can be concluded that the buoyancy driven forces have influence only below a certain threshold of wind velocity. The paper helps to better understand the behaviour of the ventilated façade installed in a building and allow designers to quantify the influence of the façade on the global building energy balance.