Glass Transparency and Thermal Cushion

The effect of extraordinary transparency at SANAA’s Glass Pavilion is intrinsically related to the problem of heating and cooling and, subsequently, the architects’ integration of engineering with architecture. Questions of heating and cooling glass buildings challenged modem architects from their early days. Bruno Taut’s Glass Pavilion in Cologne and Paul Scheerbart’s book Glasarchitektur, both dated 1914, foreshadowed a future in glass buildings with double-glazed walls, including their capacity to solve glass’s critical weakness, thermal transfer. Like Taut, Scheerbart believed that technology was “the formative agent of the current culture”²⁸ and saw the need to experiment with glass architecture enabled by iron structure. Taut invited Scheerbart to write 14 mottos in rhyming couplets in German, each in 28 letters. These words were incised around the concrete at the base of the dome. One of the 14 phrases by Scheerbart explicitly referenced a double glass wall: “Greater than the diamond is the double walled glass house.”²⁹ Scheerbart speculated that interaction between two sheets of glass held a greater potential than a single lite, anticipating the transparent poché space between the curved sheets of glass at Toledo. In Scheerbart’s prophetic 1914 book Glasarchitektur, he contemplated double glass, looking far ahead of his time to speculate what glass architecture could be. He wrote, “As air is one of the worst conductors of heat, the double glass wall is an essential condition for all glass architecture. The walls can be a meter apart - or have an even greater space between.”³⁰

What is remarkable is not only the dimensional similarity between the perimeter air circulation zone at SANAA’S building in Toledo and what Scheerbart describes as glass walls “a meter apart.” It is also that the “light between these walls shine outward and inward.”³¹ The play of light between the layered sheets of glass at Toledo makes the reflections and their refraction appear superimposed on each other, constructing a delicate, diaphanous space, and suggesting a new sort of transparency. Moreover, Scheerbart forecast double glazing as a response to the problem of heat conduction with glass. What Taut and Scheerbart envisioned with two sheets of glass spaced about a meter apart bears a notable resemblance to the 30-inch air space at the Toledo Glass Pavilion.

There were other modern architects who notably pioneered environmental control in glass façade buildings. Early examples of double glass façades first appeared in industrial buildings, including the Steiff factory in Giengen, Germany (1903) and Olivetti’s IGO factory in Ivrea, Italy by Figini and Pollini (1937—1939). These buildings were designed for laborers who worked by natural daylight and ventilation. In the late 1920s, Le Corbusier gave the name “neutralizing wall” to the double skin façade that cuts heat transfer between the inside and the outside and, instead, circulates mechanically conditioned air in the cavity. He proposed the neutralizing wall for the League of Nations assembly hall in Geneva (1927), the Tsentrosoyuz office building in Moscow (1929-1935), and the Salvation Army City' of Refuge in Paris (1930-33). The double façade was only implemented at the Tsentrosoyuz building, but with operable windows. The City of Refuge was built with a non-operable airtight glass façade, but was only single-glazed.³²