Energy Performance Evaluation of a Ventilated Façade System through CFD Modeling and Comparison with International Standards

Abstract

Ventilated façades can help to reduce summer building thermal loads and, therefore, energy consumption due to air-conditioning systems thanks to the combined effect of the solar radiation reflection and the natural or forced ventilation into the cavity. The evaluation of ventilated façades behavior and performance is complex and requires a complete thermo-fluid dynamic analysis. In this study, a computational fluid dynamic (CFD) methodology has been developed for the complete assessment of the energy performance of a prefabricated timber–concrete composite ventilated façade module in different operating conditions. Global numerical results are presented as well as local ones in terms of heat flux, air velocity, and temperature inside the façade cavity. The results show the dependency of envelope efficiency on solar radiation, the benefits that natural convection brings on potential energy savings and the importance of designing an optimized façade geometry. The results concerning the façade behavior have been thoroughly compared with International Standards, showing the good accuracy of the model with respect to these well-known procedures. This comparison allowed also to highlight the International Standards procedures limits in evaluating the ventilated façade behavior with the necessary level of detail, with the risk of leading to design faults.

Desempenho térmico de fachadas ventiladas opacas

“…Stazi, Veglio and Di Perna (2014 ) showed that lower facades perform worse because they receive ground-reflected radiation and, due to the reduction in the air column, there is an increase in the temperature of the channel, reducing the internal-external temperature difference. Pastori et al (2021) conclude that it is essential to consider the efficiency of the facade along its height to correctly design the energy performance of the building.…”

“…The light color reduced the thermal load by 80% and the dark one by 31% compared to a non-ventilated facade. According to Pastori et al (2021), the light color (α=0.4) allowed a heat flux reduction of 40% when compared to the dark color (α=0.8). Marinosci, Semprini and Morini (2014) highlight that the thermal performance of facades is very sensitive to the radiant properties of outer layer.…”

Analysis of condensation and ventilation phenomena for double skin façade units

“…If energy efficiency is not improved, the energy demand is expected to increase by 50% by 2050 (Wu¨est and Luible, 2018). High energy-efficient building envelopes have a primary role in reaching a high sustainability and improving the indoor comfort (Baldinelli, 2009;Bazjanac et al, 2002;Lollini et al, 2010;Pastori et al, 2021). In this regard, Double Skin Fac xades (DSFs) are a relevant technology trend for high-rise glazed building envelopes (Aksamija, 2017), because of their high grade of transparency and their possibility to 'adapt' to outdoor conditions thanks to their ventilated cavities and integration of solar shadings, allowing to reach acceptable thermal and visual performances.…”

Eco-Efficient Ventilated Facades Based on Circular Economy for Residential Buildings as an Improvement of Energy Conditions

“…The facade is the part of the building where the most energy is lost [15], because of this, it is essential to develop facades for the rehabilitation of buildings. In recent years, plenty of studies have been developed to analyze the energy improvements involved in the implementation of ventilated facades as rehabilitation [15][16][17].…”