© Farshid Assassi
© Farshid Assassi


Public Library Des Moines

Order Volume

3.500 m²


David Chipperfield Architects with
Herbert Lewis Kruse Blunck Architecture





Public Library Des Moines

Des Moines, Iowa, USA

Insulating Glass with Expanded Copper Inlay - OKATECH: Attractive Design and Sun Protection Function

More than being a shelter for books, the central library for the city of Des Moines, Iowa/USA, acts as a community centre with a wide range of educational services. In addition to collections of books, periodicals and other media, the library comprises a collection of historical documents and extensive youth and children’s facilities such as classrooms and play areas. As another service to the local community, the building houses a conference centre and commercial space.

The striking feature of the design concept is the 3,500 m² glass façade. For David Chipperfield Architects, OKALUX in Markt­heidenfeld/Germany developed an insulating glass with an expanded copper inlay which gives glass facades a warm, metallic glow and an appealing glint when the sun shines on them. The expanded copper inlay produces soft light in the interior of the building and provides effective protection against sunlight and glare. The glazing is semi-­transparent. The fine-mesh perforation pattern offers an elegant “one-way function”: People inside can look out, but people outside can’t look in.



The expanded copper inlay is not only a distinctive design element, it also performs the function of a directionally selective daylight system. The countless, asymmetrically arranged metal perforations act as shading elements in miniature. When the sun is high, the expanded metal screens it out completely and when the sun rays are vertical, the total solar energy transmission reaches a value of 0.13, increasing for smaller elevation angles. This means seasonal sunlight protection for the building in winter and heat protection in summer. OKATECH forms a visual and technically perfected synthesis of sun protection and transparency.

OKALUX, Marktheidenfeld, developed this new insulating glass at the request of David Chipperfield, London, for the Public Library in Des Moines, Iowa (USA). Most of the library was triple glazed: 6 mm single-pane security glass on the outside, an expanded copper inlay in the 2 mm cavity between the first two panes, 6 mm single-pane security glass with a sun and heat protective coating in the middle and another 6 mm single security glass pane covering a 14 mm air-filled space.

In addition to this, double glazing was used with 6 mm single-pane security glass on the outside, an expanded copper inlay in the 2 mm cavity between the panes and 6 mm single-pane security glass on the inside.