The Berlaymont building is a double ventilated glass façade building with glass louvres.  The inside glazing layer is made of traditional double glazing and the outside façade is made of rotating glass louvres.The louvres are made of two glazing leaves with a multi-layer film inside.  The external face of the micro-perforated film is white, in order to reflect the daylight.  The louvres inside colour is black, so as to allow the view towards outside.

The louvres are organised in frames of 2m high and 3.3m width.  Each frame contains 6 superimposed elements.  The frames are organised by sectors, each of them including 3 frames that are interdependent for the louvres rotation command.The louvre rotation is thus made by sectors (on the whole 433) thanks to engines (on the whole 748), that are ordered by a central unit.The louvre control is a function of:-          The sun position (date and time) ;-          The louvre location on the façade (orientation et height) ;-          Information collected by the meteorological sensors located on the roof (wind, horizontal illuminance, rain and temperature).

The louvres are tilted according to these parameters and make function either of shading (from 0° to 60°) or of reflectors, in order to increase the luminous penetration (110°), when there is no direct sun. For each sector, the sun height and solar mask have been calculated, as a function of the time, and it is from this calculation that the louvres slope is determined.  For the shading function, the louvres are oriented perpendicularly to the sun.  As the rotating movement is only possible by 10° step, the louvre will be perpendicular to the sun rays, with ± 5° accuracy.

Under cloudy sky, the daylight factor values are strongly dependent on the louvres slope.  When the louvre slope is equal to 110°, the daylight factor increases by 33% compared to the value obtained with a 90° slope and by 100% compared to the value obtained with a 0° slope. The luminous direct transmittance of the louvre is about 70%.  This value is constant as the louvre stays perpendicular to the sun.