Parametric optimization of multifunctional integrated climate-responsive opaque and ventilated façades using CFD simulations

The design and application of dynamic façades have gained attention in recent years as new high-performance building façade alternatives. In this study, the optimization of a novel opaque dynamic façade, the MICRO-V (Multifunctional Integrated Climate-responsive Opaque and Ventilated) façade, is investigated. This façade is comprised of different components to regulate the flow of heat, air, and moisture into buildings dynamically with daily and seasonal responses using an integrated ventilation module, phase change materials (PCM), and an adjustable insulation system. This façade acts as a decentralized ventilation system, in which the fresh air is pre-conditioned using the thermal energy storage provided by the PCMs, and the heat recovery inside the ventilation module. The aim of this paper is to optimize the conceptual façade design using parametric simulations by quantifying the performance of the MICRO-V facade. Multiple parameters, among which the geometry, the material properties, and the airspeed were tested. CFD simulations were performed in both the heating and the cooling seasons in a continental climate (Toronto, Canada). The pre-conditioning efficiency of fresh air in the façade was 73% in the summer week and 65% in the winter week. Including the PCMs to condition the air resulted in an average increase of air temperature in the winter by 3 °C, through solar gain storage, and helped to reduce the extreme temperature by 5 °C on extremely hot summer periods. The study showed the thermal resistance in the façade could be increased and decreased as a function of airflow in the façade, which is a potential way to control the overall heat gain and heat loss through the façade annually. The façade-scale simulations showed the necessity of this type of analysis prior to whole-building simulations to accurately represent the façade's performance.