Simulation of the thermal performance of a geometrically complex Double-Skin Facade for hot climates: EnergyPlus vs. OpenFOAM

Simulating the thermal performance of Double-Skin Facades (DSFs) is a complex issue faced by many architects who attempt to utilise them for energy-saving, acoustic, and aesthetic benefits. EnergyPlus is among the most widely used building simulation programs, and its capability of simulating DSFs is controversial which derives the need for further investigation. DSFs are usually designed with flat surfaces, and thus the simulations performed in previous studies to verify the accuracy of EnergyPlus were almost always dealing with simple flat facades. This paper presents a preliminary investigation into the reliability of EnergyPlus in simulating the thermal performance of a geometrically complex unconventional DSF. The increase of geometrical complexity increases the challenge of DSF simulation. Using CFD, the paper also aims at having a better understanding of the thermal performance of the DSF which was not possible using only EnergyPlus. A numerical experiment is performed in which two models of a DSF are compared; one simulated with EnergyPlus and the other with OpenFOAM CFD software. The average cavity temperature and the volume flow rate of the air at the outlets are compared. Results of the comparison showed minor differences between them, which gives a positive indication of the potential of EnergyPlus in handling complex geometries with complex physical phenomena. Conducting physical experiments on built prototypes to verify the results represents both the main limitation of this work and its future plan. The paper discusses some of the challenges that prevent architects from using CFD, and how they can be addressed, then ends with some design recommendations for DSFs in hot climatic contexts.