Simulation and validation of plain and low emissivity cavity Opaque Ventilated Façade configurations

Opaque Ventilated Facades (OVFs) are effective building components particularly in mitigating cooling needs. When their implementation in a building needs to be assessed, a building-level analysis is necessary. This approach though, presents several challenges, as whole-building simulation tools do not incorporate direct OVF models. There are, however, simulation paths someone can follow which provide more approximate solutions, whose precision though, remains uncertain due to lack of existing validation studies. EnergyPlus is a widely used simulation tool, and the Airflow Network Model (AFN) integrated into it offers the capability for airflow simulations, but has not, to date, been evaluated for OVF simulations. In this study, a simulation model was developed in EnergyPlus using the AFN to simulate an OVF, which was validated against experimental data. The model was built and validated for two façade heights and for a façade embedding a reflective/low-emissivity surface in the cavity. All three model variations were successfully validated against the experimental data, demonstrating that the AFN can be used in building simulations to accurately predict the thermal performance of an OVF. Validation also revealed that surface temperatures are the model’s most reliable variables. Using the validated model to analyze the OVF’s performance, it was revealed that it contributes to 48% less heat gains than an unventilated facade, while the addition of a reflective coating yields an OVF system approximately 21% more effective during the cooling period.