Design of Natural and Hybrid Ventilation

The effectiveness of natural ventilation, i.e. its ability to ensure indoor air quality and passive cooling in a building, depends greatly on the design process. Mechanical ventilation systems can be designed separately from the design of the building in which they are installed. They can also be installed in existing buildings after a few modifications. In contrast, ventilation systems using only natural forces such as wind and thermal buoyancy need to be designed together with the building, since the building itself and its components are the elements that can reduce or increase air movement aswell as influence the air content (dust, pollution etc.). Architects and engineers need to acquire qualitative and quantitative information about the interactions between building characteristics and natural ventilation in order to design buildings and systems consistent with a passive low-energy approach.Natural ventilation can be used to provide fresh air for the occupants, necessary to maintain acceptable air quality levels, and to cool buildings in cases where the climatic conditions allow it. Natural ventilation is caused by pressure differences at the inlets and outlets of a building envelope, as a result of wind velocity and/or stack effect