Transparency in Preservation
Walls of Glass
Traditional load-bearing masonry architecture is often characterized by large areas of solid masonry and much smaller areas of glass. It was not until construction technology advanced that larger openings became typical in masonry facades. Increasingly since the Industrial Revolution, the ratio of solids to voids in the facades of low-rise structures and buildings for which daylight for working conditions or sunlight for growth or health were critical (e.g., factories, greenhouses, sanatoria, etc.) dipped significantly.
By the end of the 19th century, the use of glass and glazing to enhance limited or nonexistent artificial interior-lighting conditions in both residential and commercial buildings became customary and indeed integral to many early modern buildings, ranging from factories like the Fagus Shoe Factory, built 1911 to 1913, by Walter Gropius and Adolf Meyer, to the later Van Nelle Factory by the architectural firm of Brinkman & van der Vlugt.
The ability to manufacture larger sections of glass affordably and the discovery of sunlight's importance to health and well-being both contributed to the acceptance of the extensive use of glass and glazing in 20th-century architecture. More extensive glazing can also be found in residences, pavilions, department stores, sanatoria, and other buildings in which daylight was critical to work, comfort, and wellness. The Zonnestraal Sanatorium in Hilversum, Netherlands, and the Barcelona Pavilion are just a few of the many other prewar examples.
The postwar aesthetic continued and even expanded this pervasive use of glass, notably in residential buildings (some extreme examples are the Glass House in New Canaan, Connecticut, and the Farnsworth House in Plano, Illinois) and in corporate office towers like the Seagram Building and Lever House in New York.
The contrast in the use of glass between traditional construction and modern architecture is best seen in historic photographs of, for instance, Lever House on Park Avenue in the 1950s. A striking contrast is presented between the glazed curtain wall of Bunshaft's design and the surrounding late 19th- and early-20th-century masonry buildings.
It is not the scale of Lever House that contrasts with the surrounding buildings, but rather the juxtaposition of the glass and steel against the smaller window openings in the adjacent masonry facades. The placement and orientation of the tower, which does not completely fill the block from lot line to lot line, further emphasizes this contrast through the creation of the large open space adjacent to the glazed facade, allowing light to enter all floors equally.
Today, Lever House is only one of the many curtain walls that line Park Avenue and the surrounding streets. The transparency of all of these buildings directly affects how they are perceived from the street level during the day and at night. Interior details and finishes, once hidden behind masonry walls or wood-frame structures, become part of the overall exterior architectural expression.
Inconsistencies in the application of current preservation policies to modern architecture occur largely because the regulations were developed for more closed, conventional architecture. In that architectural expression, the separation between outside and inside occurs visually. The regulatory authorities devised discrete exterior and interior designations and protections in response.
But in modern buildings this separation is (intentionally) obscured and that distinction does not exist or is no longer possible, confounding existing preservation policies and landmark designations in the United States. The Seagram Building provides a dramatic example of the importance of maintaining the original unity of the visual intent at night through its ceiling and lighting design.
The impact of this exterior-interior relationship is twofold. First, the building must be addressed as a totality: interior renovations will have a far greater impact than they would on a building from an earlier period, and their implications for the exterior must be considered. Second, an adaptive use selected for the interior needs not only to be compatible with the inside, but also to be evaluated in terms of its impact on the exterior's appearance.
Too often the visual cohesion of an exterior is destroyed because of the wide variety of interior treatments created in a vacuum, without any consideration of their implications on the exterior — or simply to accommodate the (temporary) needs of the occupant at the time. Due to the prominence of the visual statements interior treatments carry — both during the day and at night — any modifications to the transparency of these glazed buildings must be temporary or movable, in the form of elements such as drapes or shades.
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Theodore H.M. Prudon, Ph.D., FAIA, was educated at the University of Delft, Netherlands, and Columbia University. He is a partner of Prudon & Partners, based in New York City, and teaches preservation at Columbia University's Graduate School of Architecture, Planning and Preservation. Prudon is the president of DOCOMOMO US and a board member of DOCOMOMO International, groups dedicated to the study and protection of significant works of Modern Movement architecture, landscape design, and urban planning around the world.
This article is excerpted from Preservation of Modern Architecture by Theodore H.M. Prudon, copyright © 2008, with permission of the publisher, John Wiley & Sons.