Thursday, January 02, 2014
Materials shape our built environment, with architectural glass playing a dominant role in defining our current cityscapes. But while the attributes of transparency are indispensable in many applications, the formability of architectural glass is limited. As designers continue to search for greater freedom of architectural form, recent advances in molded, composite concrete technologies suggest an opportunity. The question is: to what extent will molded materials shape the built environment of tomorrow?
At the center of the composite discussion today is fiber-reinforced polymers (FRP) and their potential for application in the building facade. The advantages are many: an extremely favorable strength-to-weight ratio, highly customizable engineered properties, a resistance to surface cracking (such cracking is a frequent problem with its close material cousin, glass fiber reinforced concrete (GFRC)), and a higher durability when compared to many traditional building materials (such as environmentally exposed finished metals, which are prone to deterioration from rust and corrosion).
Leading industry professionals are already developing these molded technologies into built realities; prime among them the San Francisco Bay area firm of Kreysler & Associates. Kreysler is currently fabricating the oversized sculpted FRP facade panels for the San Francisco Museum of Modern Art (SFMOMA) expansion designed by the Norwegian architectural firm Snohetta. Equally strong is interest in the material from academics, including California Polytechnic State University–San Luis Obispo, whose bachelor of architecture program was just ranked first in the nation by DesignIntelligence. Relevant in this regard is the program’s top spot in the “Construction Methods and Material” category, where faculty such as associate professor Mark Cabrinha and assistant professor Jeff Ponitz lead students in materials-based seminars supplementing their studio work.
For the seminar’s final project, five student teams presented projects with a single requirement: develop a process and concept for an FRP facade system. Results varied from panelized systems, grid based designs, cylindrical forms and tessellated patterns. Concepts included both barrier wall and rain screen systems.
“The issues with FRP are compelling,” Cabrinha says. “We use curvature for strength, but how much is enough? How much is coming from the material, and how much is coming from form?”
The review panel included three integrally involved industry professionals to weigh in on the design, constructability and material properties of the student projects: Shawn Gehle, principal and design director at architect Gensler’s Los Angeles office, Dan Green, vice president at national facade contractor Enclos, and Joshua Zabel, director of digital fabrication at Kreysler & Associates. Gehle noted “the range of ideas presented is a great indicator of the material’s potential.” Green offered design and constructability considerations, ranging from the thermal expansion properties of FRP (it’s similar to aluminum), its interaction with adjacent wall systems, and his surprise with the student’s “interest in developing cost effective designs for the future.”
The application of FRP as a building facade material is not without its challenges. There are few examples of the large-scale application of the material in commercial building projects, and a resulting reluctance by many risk-averse building owners to its inclusion in their construction programs. The primary limiting factor has been fire code restrictions, specifically National Fire Protection Association NFPA 285: Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components. Recent advancements, however, backed by successful testing — the approval of Kreysler’s SFMOMA project being the most recent example — have opened the door for the widespread adoption of this exiting material in commercial building facade applications.