Measuring and estimating airflow in naturally ventilated double skin facades

• Airflow measurements inside a naturally ventilated double skin facade (DSF).
• Wind pressure coefficients determined from wind tunnel tests.
• Airflow estimates from a simple model accounting for the thermal and wind effects.
• Comparison between experimental and a simple model results.
• Discharge coefficients of the DSF system estimated for different blind slat angles.

An accurate assessment of the airflow in naturally ventilated double skin facades (DSF) is crucial for a correct design and performance evaluation. Measuring and predicting DSF airflow is not a straightforward task, given the stochastic nature of the wind, which can assist or oppose the buoyancy force. The present paper resumes the results of airflow measurements inside a naturally ventilated double skin facade using a tracer gas technique. The tests were performed on an outdoor air curtain (OAC) DSF test cell with a movable slat venetian blind. Measurements with no active shading and at night were also performed. Outdoor and test cell air gap temperatures were continuously measured and wind pressure coefficients were determined from wind tunnel tests. Experimental results were then compared to those obtained by a simple model taking into account both thermal and wind effects on the facade. From this comparison discharge coefficients were estimated, which can be used for characterizing the DSF behaviour.