Naturally ventilated double-skin façade with adjustable louvers

Naturally ventilated double skin façade (NVDSF) absorbs solar radiation to introduce natural ventilation. It has been proved with significant importance in building energy-saving, and louvers on the NVDSF could be essential in real-life applications for the adjustment of uncomfortable flow. However, the impacts from this practical feature of adjustable louvers on the buoyancy-driven airflow are still not known. Motivated by this, this study addressed the influences of an operable outlet louver on the natural ventilation performance of an NVDSF, with louver angles of 30°–150° under various solar conditions (i.e., solar altitude angles within 10°–80° and direct incident solar radiation within 50–1,000 W/m2) for two types of glazing materials (i.e., regular and low-e glazing). A validated CFD model was used to solve the solar radiation and natural ventilation coupling problem between two semi-transparent façades. The results show that the outlet louvers’ influences are significant and should not be ignored in practice. Compared to the no-louver case, upward-opening louvers (louver angles within 30°–67.5° in this study) can promote the ventilation - the optimal louver angle at 45° can enhance the natural airflow by 10–14% for two types of glazings; whereas downward-opening louvers (112.5°–150°) will weaken the natural flow by 6–9% per increment of 10° in louver angles. Empirical models were also developed to quantify the impacts of the typical solar conditions on natural ventilation performance. The obtained power-form functions between the ventilation rates and solar factors (altitude angle and incident radiation) show similarities between NVDSFs and solar chimneys.