ABSTRACT
The most common device for natural ventilation is the operable window for which the mechanism involved is primarily wind-driven ventilation, although buoyancy may have a non-negligible effect. Stacks and chimneys are used for buoyancy-driven ventilation; when designed to take advantage of the wind, stacks become wind catchers. Neither the operable windows, nor the vents described in the following section are well suited for large airflow rates when protection against rain, insects and burglary is required. One of the reasons for replacing natural ventilation with mechanical ventilation is the external noise, often disturbing in the urban environment. Stack ducts have long been used to either introduce outdoor air in buildings or to extract vitiated air from rooms. In windy areas, wind catchers tower on top of buildings to take advantage of higher wind velocity. The Siemens building in Dortmund was renovated with a double-skin façade after a fire in 1996.
