Biologically inspired compliant building façade systems with tunable heat transfer capabilities

Abstract

Energy consumption for building thermoregulation is a major contributor to the environmental impact of our built environment. Building envelope systems that actively tune their heat transfer rate in response to environmental stimuli and leverage the free energy the exterior environment has to offer, thus represent a promising solution to make building thermoregulation more energy efficient. This dissertation investigates the means and methods to develop façade systems that tune heat flow by drawing inspiration from nature and leveraging the unique properties of compliant materials. The research encompasses a wide range of highly complementary fields including thermodynamics, materials science, and soft actuators, all of which are framed within the context of employing nature’s design rules for tuning heat transfer and generating motion. From these interdisciplinary investigations, two novel thermoregulatory concepts are presented in the form of mechanically actuated designs made from the optically transparent elastomer polydimethylsiloxane (PDMS). Inspired by the chromatophores in coleoid cephalopod skin, the first example is a novel infrared light-modulating technology constructed from a PDMS film with a thin gold surface coating. Inspired by the cutaneous cardiovascular system in endothermic homeotherms, the second example consists of a PDMS-based vascular device that modulates conductive and convective heat transfer. Through both experimental projects, the work investigated how to translate biological design principles into our own concepts for tunable systems, how to fabricate these systems, how they can be actuated, how to evaluate their performance, and where and how to apply them in our building envelopes to benefit building thermoregulation. To achieve these goals, the research encompasses an extensive literature review of the biological precedents, iterative and functional prototyping, and performance analysis through numerical modeling and experimentation. The results from these efforts demonstrate how the new concepts provide opportunities for optimizing heat transfer and utilizing freely available solar energy and wind, and consequently, significantly reducing energy use for building thermoregulation. Fundamentally, the work demonstrates how a design strategy that integrates science, technology, and design creates new design opportunities for façade systems with tunable heat transfer.