An ecologically-minded high-rise

Using state-of-the-art technology to achieve an environmentally friendly high-rise

In 1991 Germany's fifth largest corporate group put a major architectural project out for international bids. RWE AG was looking for a new home for its Headquarters. The contract was awarded to Düsseldorf architects Ingenhoven, Overdiek, Kahlen & Partners, whose superlative design produced the building. The move is planned for March 14, 1997. At 162 meters (including antenna), it is the tallest building in the state of North Rhine-Westphalia. Cost of construction was ca. 150m Euros. Even more surprising is another superlative: RWE's new Headquarters building is the world's first environmentally friendly high-rise.

This project marks a decisive turning point in high-rise construction, which had previously been dominated by the American principle of strict separation of the interior from the outside environment by means of air-conditioning. Construction of the RWE Group Headquarters heralds the advent of a new breed of multi-story building which no longer hermetically seals the interior from the vagaries of the weather outside, but instead benefits from outside conditions in an ecologically useful and environmentally friendly way. This is certainly not just for the sake of saving electricity - it also benefits the tower's "inhabitants," RWE's staff, who can enjoy fresh, naturally conditioned air, individual control of air-conditioning and lighting, the benefits of natural daylight and an unimpeded view of the outside world.

The shape - lots on inside, a minimum on the outside

Assuming an equal circumference, the circle has the largest area of all one-dimensional shapes. This simple principle of geometry was the basis upon which the aerodynamics, illumination, floor space layout and element usage were optimized. The same mathematical principle can be seen both in the shapes of the industrial structures found in the Ruhr Valley - from chimneys and pipelines to water towers and gasometers - as well as in nature. The principle holds true in the biological world too: a small amount of skin covering a large volume keeps the body warm.

A glass skin that breathes

An ingenious system ensures a constant supply of fresh air to the rooms in the building. The two courses of glass that form the facade create a type of miniature winter garden which allows air to pass through to the inside without causing drafts.

A lesson from aeronautical engineering

The principle of a fish's mouth is used in aircraft construction. Air passes through its aerodynamic "gills" into the plenum without any irritating noise. There it heats up, rises and exits at the top. Sun control slats are recessed into the underside of the fish's mouth. The upper sides can be converted into running boards for the window cleaners by means of a damper.

Cranking up fresh air

The RWE Tower is not a glass cage. It is a building that's in harmony with its surroundings. Using a crank like this one the windows can be opened - even on the 30th floor - so that air and sounds from the outside world can gently drift into the staff's offices.

The right working atmosphere at the push of a button

Unlike the fully air-conditioned and energy-wasting high-rise buildings of the 70s and 80s, this new building puts control into the hands of the people who work in it. Every employee can independently adjust illumination and sun control or heating and cooling in his or her immediate vicinity. This is thanks to a control panel located in each office.

Wind tunnel engineering

Numerous experiments were necessary to test the airflow behavior of a naturally-ventilated multi-story building such as the RWE Tower. These were carried out on a scale model in a wind tunnel. This allowed information to be gathered, for example, about the forces acting on the glass facade, about optimum ventilation in a building of this type, and about the effects all this would have on the behavior of airflow around the neighboring buildings. Yet another superlative: The RWE Tower is the first high-rise to have been designed in a wind tunnel.