Experimental and CFD study of ventilation performance enhanced by roof window and mechanical ventilation system with different design strategies

Abstract

Ventilation performance could influence thermal comfort and building energy. This study aimed to investigate the ventilation efficiency enhanced by roof window and mechanical ventilation system in the first certificated Active House building of China. The artificial and natural ventilation strategies were evaluated and compared quantitatively. The methodology was integrated by on-site experiment and CFD simulation: air exchange rates were calculated based on tracer-gas-concentration-decay experiment; CFD simulation helped in analyzing the mechanism by visualizing airflow velocity magnitudes. Findings can be summarized as follows: (1) The artificial and natural ventilation enhancement strategies of using mechanical ventilation and roof window systems have been compared quantitatively and demonstrated to be significantly effective. (2) The ventilation efficiency enhanced by roof window can be 1.62 times higher than the mechanical ventilation system under the particular condition. (3) The design of roof window and opening on the door is crucial for the generation of dominant air flow in the ventilation promotion. (4) The experiment and simulation suggest that the geometry of indoor space, local climate condition and heating strategy of using ground-source heat pump would influence the ventilation performance synthetically. Holistic design strategy is highly recommended for sustainable design considering multiple elements comprehensively.