Ever since they set up their firm in Philadelphia eighteen years ago, Stephen Kieran and James Timberlake have been experimenting with new technology. These two architects are interested in understanding the essence or the potential of different materials, as well as the ways in which one can combine these materials through poetic details.
Reprinted with Permission of Costruire in Laterizio Magazine
by Andrea Quilici
Today's technology offers interesting opportunities to experiment new formal solutions in masonry construction: for example the Marks Center for Science and Technology in New York City.
Ever since they set up their firm in Philadelphia eighteen years ago, Stephen Kieran and James Timberlake have been experimenting with new technology. These two architects are interested in understanding the essence or the potential of different materials, as well as the ways in which one can combine these materials through poetic details.
Among the new systems that KieranTimberlake Associates has been interested in studying is the Pressure Equalized Wall. Developed in Canada, this system was first presented to the public in 1963, in an article by G.K. Garden published in the Canadian Building Digest (CBC) 40. Garden brought up the problem of water penetrating in a cavity wall as a result of a difference in pressure on the exterior and interior sides of the wall. By penetrating inside the cavity wall, water can cause the corrosion of metal ties, the formation of efflorescences on the exterior facade, as well as on the inside, humidity spots which in turn can alter the interior's comfort level. At the roots of these problems are: 1) the grouting drying process; 2) the presence of excessive water in the masonry; 3) a capillary action due to the difference in pressure between the exterior and interior of the wall.
In a traditional wall system, a cavity is made to stop interior's water from penetrating from the exterior to the interior; ventilation allows the interior exceeding water to dry; finally, open joints at the bottom of the wall construction ensure the evacuation of condensation water. There is only one problem that the traditional cavity wall doesn't account for: the pressure differential between different layers of the wall construction and the consequent capillary action. The Canadians in question developed a system that keeps the advantages of the cavity wall system, while also solving the problem of water penetration due to a capillary action (when water is drawn into the cavity through the masonry, as well as through imperfect window or door seals). Once inside the cavity, water can move to the building's interior through other wall imperfections such as construction joints or a failure of waterproof membranes or seals. The phenomenon is particularly acute at the corners of buildings, where the wind's directionality can create enormous differences in pressure between the windward and leeward sides of a wall.
According to the Canadians who researched this issue, one can solve the problem by creating a series of rigid compartments inside the cavity and -- instead of sealing the joints -- by opening the exterior wall to the cavity. This system causes the air pressure to equalize, making it difficult for water to penetrate and ensuring that any water that should pass through will evaporate quickly. More specifically, this system is made up of:
Compared to the double wall, the Canadians' system increases the exterior wall's performance. The creation of different compartments maintains the advantages of a cavity wall, while also eliminating the problems caused by the penetration of rain water: the latter is kept from entering, or it is made to evaporate very quickly along with any eventual condensation water.
The Marks Center
As the description of this system shows, the pressure-equalizing wall solves the problem of water penetration. At the same time it offers an opportunity to rethink the articulation of a brick facade. KieranTimberlake Associates embraced this opportunity to reconsider the meaning of an exterior wall. At the Marks Center of Brooklyn Polytechnic Preparatory county day school, in New York City, Kieran and Timberlake decided to use the exterior wall as a site on which to experiment with this new technology. They seem to have thought of this project as an imaginary laboratory which -- most appropriately -- eventually became laboratory for science and new technologies. The building was initially conceived as an extension of the existing school. Later, during the schematic design phase, it became a single quasi-cubic object of 4 stories and 48 feet, placed in the middle of an open space. The lab was then connected, via a bridge, to a new terrace/ path designed in front of the existing building. The simplicity and repetitiveness of this program, the four floors of labs, and the form of the building itself all risked making the facade monotonous and repetitive. Instead, the pressure-equalizing system and the need to compartmentalize the interior cavity allowed the architects to create a panelized wall which ultimately gives the wall's facade a compelling rhythm and theme. This system also allowed them to reduce the wall to a more human scale, while refocusing attention on the wall's modular component: the brick itself. The brick is in fact framed, horizontally, by steel profiles and, vertically, by aluminum brake-metal profiles. The joints between the bricks and the profiles are left open to allow the pressure to equalize in the interior compartment. This detail also solves the problem of control joints. As a result, this facade can be read as a catalogue of the joints necessary to the building of a brick wall: control joints are typically required a) in -- or adjacent to -- corners (at the Marks Center, the wall is in fact disjointed at the corners; the brick is free to expand; the joints are open and the space between the two planes is occupied by down-spouts); b) at the sides of openings, when the latter are over 6 feet wide; or, as in this example, at the sides; or in the center when these are less than 6 feet; c) every 90/100 feet of wall; d) finally, control joints are required at steel angles to support masonry veneers, often at each level.
From a formal point of view, the building's exterior wall can be viewed as a series of four panels that rotate around the rain water conductors to form a box which contains the laboratories within. This box opens up only on the entrance side, where a separate plane runs horizontally, thereby defining the different function of the internal stairs that connect the building vertically. In order to emphasize the separation of these vertical planes, a continuous glass window is inserted. The other openings, in turn, are equally designed in aluminum brake-metal profiles, and their joints are left open so as to allow the functioning of the wall structure. A number of other details ultimately contribute to making the building more interesting to the user: they insert formal elements which instill a compositional tension, and stimulate in the user that process of architectural discovery which is at the heart of KieranTimberlake's philosophy. Among these details, one should at least mention the transition between the brick wall and the ground or sky. Indeed, given that the brick wall has lost its bearing function and that it is made up of panels that dematerialize the facade, there is no longer any need for the brick wall to touch the ground. Here, too, a steel profile can help us in the transition; it exalts the lightness of a wall which now is nothing more then a protecting screen against water. The coping equally enhances the lightness and ephemerality of the wall, thanks to its light and continuous lines. At the entrance, where the wall runs horizontally to make room for the stairs, there is a cantilevered roof, along with a bridge that connects the building to the terrace, the path to the entrance. Finally, the gutters have become architectural elements which, with their shadows and asymmetrical positions, create moments of tension within the uniformity of the facade: they are elements of contradiction or ambiguity, as Robert Venturi would call them.
The exterior wall thus reveals its true identity in the Marks Center project. Modern technology no longer uses brick as a bearing structure; instead, the wall functions as a form of protection against water. In addition, it also can be made to illustrate its own tectonics. This last point is a guiding principle for Kieran and Timberlake, who insist upon the modern meaning of the ancient Greek tekton, or tectonics, a term that initially designated a carpenter or constructor, but that now also signifies an assembly art through which technology and beauty converge to create meaningful architecture. In KieranTimberlake's office, every project is a new and unique experience: the uniqueness of place and the different design conditions inspire new formal and technological solutions. The firm also takes into account recent technological developments and the ever more restrictive wall performance requirements. But it considers these new systems or requirements not as problems that must be resolved, but as an opportunity for the architect to develop. In the architecture of KieranTimberlake, there are no immutable and eternal aesthetic choices. Their projects narrate the creative process through tectonics. As Kieran has noted, "Great architecture has never -- at its soul -- been about style. It is about the discovery of principles. Those principles are hard won -- discovered -- building by building. Those principles are recurring -- they have a truth -- a life -- beyond any individual. Their foundation lies deeply within the craft origins of architecture itself -- yet the ground for ever evolving, fertile invention is vast." Kieran and Timberlake like to involve their collaborators, clients and users in this creative process. It is therefore through the texture and juxtaposition of their materials, as well as through the detail work involved in the latter's assembly, that the student, teacher or visitor to the Marks Center in New York City is made to discover, day after day, the beauty of the architecture and of the space in which he or she lives or works.
© 1997– KieranTimberlake Associates LLP
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