LA HOJA
The commission involved creating a covering for the central space of the recently completed library at Monterrey Tec. The goal was to protect the space from rain, sun, and uncontrolled winds so that it could be used year-round. This was particularly important, because the space was underutilized and had become somewhat dysfunctional during storms, to the point that the lack of covering was creating a condition that was beginning to cause the deterioration of the building’s courtyard.
The building in which the new roof is located was designed by Sasaki and Associates in a contemporary style defined by large stone and glass planes. The rigidity of the geometry is broken by a series of bridges crossing the space at varied angels as well as stairs connecting the different levels. It was important to pay homage to the geometry and style while also introducing a more whimsical element to the design. Doing so might help bring the space to life and create a dynamic environment that would attract people, so that it would become a central gathering space within the campus.
The trees on the lush campus inspired the creation of a veil simulating leaves falling on the surface via a pattern screened on ETFE. The falling leaves were further connected to the idea of evoking fall and the moment when the semester begins, when students are positive and excited by a new beginning. The ultralightweight structure will create new patterns as the sun moves across the surface and, in turn, provide a sense of time passing as one studies in the library.
The roof is defined by both the large figure of the leaf and also by the smaller leaves that make up this figure. The leaf itself comes from a tree that is native to the area—the white poplar, or álamo blanco. In some ways, the use of the leaf is intended to create an opportunity to reflect on our relationship to the natural environment and the impact that buildings have on the environment.
In designing the specific surface of the membrane, a wide range of potential patterns were explored. Parametric modeling tools were used to design the geometry of the roof. A physics engine was then used to simulate wind blowing leaves across this surface. Each leaf had a certain number of dots. The process required multiple simulations. This allowed the team to achieve a sense of randomness. In this sense, the pattern was designed directly via digital tools that were in turn linked to the digital printing technology that ultimately fabricated the membrane.
The surface of the roof is supported by a system of ten steel trusses set at an angle that would complement the angle of the bridges and stairs below. The triangular trusses would have a varying peak point that would follow a diagonal line from one corner of the atrium to the other. While a steel member would follow this diagonal peak, additional steel members would connect the two corners of the trapezoid in order to provide added stability. Below the surface of the roof, a network of tension cables completes the structural system. The structural system in turn supports the single-layer ETFE membrane that is held in tension along the perimeter.
The roof extends beyond the edge of the courtyard. In this sense, it is a cover rather than an enclosure. A wind study suggested that if an enclosure was created, the structure would have to be much more robust because the wind entering the courtyard from below would be trapped. This would have significant cost implications. By raising it slightly above the level of the roof, hot air can escape. Extending it beyond the edge also protects the courtyard from strong winds and rain.
The use of ETFE cladding material with a printed pattern reduces the potential for heat gain within the space. In addition, the use of natural ventilation along the perimeter of the roof systems allows for heat to escape while keeping water from entering the space. At the same time, the use of an ultralightweight structure reduces the overall embodied energy of materials and carbon cost of transporting those materials to the site. The result will be a space that does not significantly add to the energy load of the building.
The process of building the roof was challenging. The building is located in the center of campus with little room for staging the construction. In addition, students would continue to use the building throughout the construction process. The client was against putting a crane in the middle of the building. This meant that all materials had to be lifted from the side. In spite of these limitations, the project was finished both on time and on budget.
The intervention not only solved the initial problem but created a space that was not there before. This made it possible to introduce new programmatic functions into the atrium that enhanced the overall functionality of the library. In some sense, it has become the heart of the campus—a point where people meet and collaborate.
