The design of the RWE façade system was influenced by the clients' desire for optimum use of daylight, natural ventilation, and solar protection. All these demands resulted in a transparent interactive façade system which encompasses the entire building. The exterior layer of the double-skin façade is 10-mm extra-white glass. The interior layer consists of full-height, double-pane glass doors that can be opened 13.5 cm wide by the occupants (and wider for maintenance). The 50-cm wide interstitial space is one-storey (3.59 m) high and one module (1.97 m) wide. Outside air admitted through the 15 cm high ventilation slit at the base of one module is then ventilated to the exterior out the top of the adjacent module. Retractable venetian blinds are positioned just outside the face of the sliding glass doors (contributes to interior heat gains?) within the interstitial space. An anti-glare screen is positioned on the interior. 

Daylight, direct solar and glare can be controlled with blinds and an interior anti-glare screen. The extra air cavity acts as a thermal buffer, decreasing the rate of heat loss between outside and inside. Fresh air is supplied through the opening at the bottom and warm air is exhausted through the opening at the top of the façade. During extreme cold conditions, the windows are closed. Warm air is returned to the central plant via risers for heat recovery in the winter. The façade provides good heat insulation in the winter and with the combination of slatted blinds, effective solar protection in the summer. 

Reference 

Briegleb, T. (edt.) 2000. High-rise RWE AG Essen. Basel: Birkhauser. 

Compagno, A. 1999. Intelligent glass façades: Material, practice, and design. Basel, Switzerland: Birkhauser. 

Hertzsch, E. 1998. Double Skin Façades. Catalog of Josef Gartner & Co. Munich: Peschke.

Question/Information: eslee@lbl.gov