The dimensions of the building were calculated to facilitate reductions in energy requirements. Office buildings are customarily 18 m or 20 m deep. Yet daylight effectively penetrates only the first 5 or 6 metres of office space. It was therefore decided that for Green Office® more than half the floors would be no more than 13.5 m deep: 6 m of office space on each facade, with a 1.5 m wide corridor at the centre. On the deeper floors (18.50 m) the central area is occupied by plant rooms, washrooms, tea rooms, etc.).
The façade is divided into 1.35-m-wide vertical strips. Every second one is a very large fixed-pane window. The other is made up of three small strips, one aligned with the concrete structure of the building, one with a motor-controlled window for natural ventilation, and one with a manually opened window. These opening lights enable the façade to be continuously adapted to the building’s heating and cooling requirements, in accordance with the weather. The level of insulation and weatherproofing provided by the façade varies, depending on weather conditions and the required comfort levels