Skin Deep: Making Building Skins Breathe with Smart Thermobimetals
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SKIN DEEP 145 Skin Deep: Making Building Skins Breathe With Smart Thermobimetals DORIS KIM SUNG University of Southern California “The skin is the interface between an organism controls as components in mechatronic systems. and its world...It is probably the most versatile With today’s digital technology and driving interest of all organ systems, having mechano-sensory and skeletal functions as well, whose relative in sustainable design, this simple material can importance is different in different groups of transcend its currently limited role as a mechanical animals. These functions can all be incorporated device to a dynamic building surface material as into our technology.” well as expand the discourse of performance and - Julian Vincent in “Biomimetics of Skins”1 bio-inspired systems in architecture. This article will present a case study project of ongoing TBM research that displays the qualities of performance and optimization in the discipline today. The term performative has become the catchall phrase in architecture that reflects the current cultural interest of comprehensiveness and, as a result, is hard to define singularly or precisely. In his article for Architecture Week, Michael Crosbie points out that performative architecture is “a fresh new way of looking at architectural design that would be more inclusive than past approaches.”2 A symposium called “Performative Architecture: Instrumentality Plus?” at the University of Pennsylvania in Philadelphia in October 10-11, 2003 and in his correlating book called Performative Fig. 1: Thermobimetal skin prior to installation. Architecture: Beyond Instrumentality, Branko Kolarevic talked about performance in architecture INTRODUCTION as a “comprehensive approach to design,” placing it above form-making as a design principle.3 The term Despite the fact that thermal bimetals (TBM), or performative means choreography, or articulation of thermobimetals, have been around for decades, the performative. It is the shift of interest to things renewed interest in its responsive natures have mutable and transient, not static and fixed. In some brought it to the forefront of what some call ways, it is a temporal condition where contexts performative architecture. A poster child for and fields continually affect the equilibrium of the sustainable design, it has been used since the organism, or architecture. It can be applied to how beginning of the industrial revolution and, more a people occupy buildings, how parts of buildings recently and commonly, in thermostats as a go together in the balancing of systems, how measurement and control system and in electrical generative rules or forms of algorithms influence 146 WHERE DO YOU STAND values and parameters, or how interactive materials be useless, if not impossible. Like many things in and systems respond to outside influences. “In nature, the answer lies in the polarity of complexity its shift to the performative, architecture has and simplicity. “Simplicity as an emanation of moved its attention from the transcendental and intelligence finds its expression in the formulation heroic projects of modernism to a more situational of simplicity as the art of the complex.”5 Form, and material understanding of architecture as a structure and material have to be developed performative act, a kind of choreography of active holistically. When understanding the complex systems in the environment.”4 Although Stephen performative principles of these three parts Turk speaks of this performative act in terms of simultaneously, a simple, comprehensive system the critical history and design of tables, namely the will be the resultant with less waste and higher Wave Table Project, this same idea of performance performance. Thinking of materials as something can be applied to many areas in the discipline of independent of form and structure is naive when architecture. looking at biological models. “Biological organisms have evolved multiple variations of form that should The Armoured Corset project exemplifies the not be thought of as separate from their structure comprehensive nature of current sustainable and materials. Such a distinction is artificial, in view design in buildings skins as a contemporary of the complex hierarchies within natural structures case study of performative architecture. Rather and the emergent properties of assemblies. Form, than present it as the definitive performative structure and material act upon each other, and architecture project, this article simply tracks the this behavior of all three cannot be predicted by development of one bio-inspired study that seeks a analysis of any one of them separately.” 6 This is way to self-ventilate buildings through its skin and, the charge of this case study. indirectly, to reduce the need for artificial cooling and additional energy/emissions waste. It relies BIOMIMETICS: RESPONSIVE SYSTEMS AND on the movement of a simple smart material called BREATHING THROUGH SKIN thermobimetal (TBM). As the outside temperature rises, each of the TBM tiles curl, opening up gaps Even during the modern movement, exterior in the surface and allowing air to pass. Like an walls in architecture were designed to be static organic skin, this inorganic matter reacts smartly and rigid. Visual access between interior and to temperature change, mimicking the opening and exterior environments was open with the use closing of surface pores. of glass and steel, but artificial climate control still determined the impenetrable limits of those Throughout the development of the project, it is glass walls. As times change, more recent public clear that focusing on one aspect of design would interest in sustainable design, energy conservation SKIN DEEP 147 and zero-emission building design has infused the It’s strong and resilient. It’s breathable. It creates industry with renewed impetus to seek alternative color through structure. Whereas that chip bag has about seven layers to do all of those things. One of solutions. With the emergence of new smart our major inventions that we need to be able to do materials, the evolution of digital technologies to come even close to what these organisms can do evolving and availability of mass-customization is to find a way to minimize the amount of material, methods, those same walls can now be designed to the kind of material we use, and to add design to it.9 be responsive, interactive and even porous, much like human skin. As a “third” skin (the “first” being Like the beetle described by Professor Benyus human skin, the “second” clothing), architecture in her lecture, bullfrogs, earthworms, bats and can, in effect, bring man closer to nature by other animals have permeable skins that allow elevating the sensitivity of the building surfaces. the exchange of gases. They can virtually breathe Wedged between two dynamic natures, man and oxygen through their skins, but lack the structural his environment, the building skin can no longer integrity present in the beetle’s exoskeleton. remain static or foreign. “Living organisms rely Inspired by this comprehensive capability of the very little on energy to solve technical problems, beetle’s shell, the TBM Armoured Corset study and it should be the main objective of biomimetics attempts to make a dynamic porous system that to show how we can similarly rid our technology at times allows the passage of air, but contains of the energy requirement, thus giving us a more its own structural stability. Hung in tension and sustainable future on this planet.”7 When designing following a catenary curve, the prototype does not building skins, the logic of biomimicry is undeniable. require any additional structural element to hold its shape. The mere flattening of the tiles when Skin is the mediator between the body and cold contributes to the tautness of the form while the environment, between the inside and the the curvature of each piece when hot allows the outside. It is the visual manifestation of a mass overall form to shrink and shrivel. With the help or volume, giving form to a grouping of organic of gravitational forces, the shape of the prototype cells. “Life is made possible by membranes. Part could adjust to any temperature without the rigid of their function is to provide a surface on or from framework of an additional structural form. Like which interactions and reactions can occur and be the beetle’s shell, the simple surface resolved controlled, and part is to provide selective barriers multiple issues by taking into consideration form, to keep reactants together and the rest of the material and structure simultaneously. world out.”8 In architecture, the basic purpose of this skin or membrane is no different than that of By mimicking, or, in some cases, conceptually animals or of humans. Not only specializing as a abstracting systems found in nature, architects, covering, the skin acts a barrier that can selectively designers and researchers may be able to discover modulate the passage of physical, mechanical and more efficient models of sustainability. Like the chemical stimuli, such as heat, water, force, and beetle in Professor Benyus’ lecture, the quest for other organisms in both directions. The function making a skin that breathes, that is strong and of each direction can be dramatically different and, resilient, that is waterproof, is the motivator for inevitably, the requirements in conflict. These this TBM project. Clearly, the surface had to be conflicts have been largely resolved in nature by responsive to allow the passage of air, but restrict evolution, but absent in building technology. Rather the invasion of water. In order to allow the body than mimic efficient systems in nature, many of to breathe, the surface is thermally activated so our technological developments, including building that areas on the surface, like pores, could open up skins, have become overly complex and heavy with when the temperature, inside or out, got too warm. many unnecessary layers like a potato chip bag, These openings would allow hot air to escape and as pointed out by the author of Biomimicry, Janine cooler air to enter.