Cross-Ventilation Measurements in Buildings: Small and Full Scales Experimental Models

International audienceIn the environmental context, night cross-ventilation combined with thermal mass of walls is a promising passive solution to reduce the energy consumption of buildings while maintaining comfort, especially during summer. We realize measurements in a full-scale apartment in real conditions and in a reduced scale model of the apartment positioned in a wind tunnel. Concerning the measurement of natural ventilation air flow rate through large openings in a real apartment, an air direction detector coupled with classical anemometers has been developed and calibrated in a controlled test room. To study the flow in controlled conditions, a 1/20th size model that takes into account the details of the apartment geometry was built. Moreover, to understand how heat is removed by the flow and the role of turbulence, we develop a micro-machined sensor able to measure the local heat flux : a 375×35×1 ?m cantilever whose deflection reflects the local fluid velocity, with a temperature-sensitive thin layer deposited on its tip. This combined approach grants access to crossed turbulent statistics, in particular the contribution of the turbulent heat-flux. Data in real buildings are compared to the measurements in the reduced scale model and the validity of the approach based on the similarities is discussed. The results of the measurements in real buildings lead to distinguish between windy and calm periods, the latest being the most critical one regarding summer comfort. During calm period, we observe reversed flows in the measuring section and the duration of their occurrence is analysed