Cross ventilation consists of forcing air circulation through the entire structure of the building and not only in the different separate rooms. The air intake and its outflow should be placed at different levels of the building’s structure in order for the fresh air to be directed towards its internal space. There are many examples of how double fa9ades are integrated into the general strategy of cross ventilation of the building.

One example is the GSW office building in Berlin (designed by Sauerbruch Hutton Architects), which has a narrow, oblong shape [1]. The double facade is applied to the long western wall. The space between the layers is not divided in any way and it acts like a powerful ventilation channel. The fresh air enters into the building through windows in the single-wall eastern facade. Subpressure in the western part of the double-glazed facade forces the air to move horizontally and sucks it outside (fig.3) with the additional support from a disc-shaped element suspended over the roof of the building.

Fig.3 Scheme of cross ventilation across the width of the building (left) and vertical cross-section though the upper part of the building with an aerodynamic element, which increases subpressure in the area inside the double facade.

Another example of using a double facade for the ventilation of buildings is a concept office building in London, which was elaborated as part of a research project „Green Building" (designed by J. Kaplicky,

A. Levete, Ove Arup&Partners) [1]. It has an unusual ‘egg-shaped" form, which is suspended over the ground on a tripod. The entire external surface consists of two layers.

Fresh air enters through intakes located at the bottom, rises to the top and enters office space, where it leaves the building through a

void space of the facade, which functions as an air evacuation duct (fig.4).

One of the well-known examples of using double facades to take advantage of natural air flows within the structure of the building comes from the Commerzbank in

Frankfurt (designed by Foster&Partners) [3]. The inter-facade void together with the internal atrium and spiral-shaped winter gardens created a system of buffer zones in which air circulates, ventilating and regulating

temperature within the entire structure of the building (fig.5).