Zero Energy Adaptive Façade (ZEAF) for Energy Efficient Buildings

Rendering of the proposed self-shading system.

Published March 18, 2016

H. Lin (CBE), J. Y. Song (Architecture), J. Shim (CSEE)

Dynamic façade systems with inexpensive material cost and a high degree of design flexibility for buildings with high energy-efficiency.

This goal of this project is to build a smart building envelope application which can control daylighting, heat gain, and loss. The needs for high performance buildings and the advancements in manufacturing industries have facilitated the design of dynamic building envelopes to replace traditional, mundane shading controls. The current dynamic shading systems adopt either glass enhancement or motorized mechanical movement. In our study, the prototype Zero Energy Adaptive Façade (ZEAF) is designed to integrate a photochemical responsive polymer sheet into building facades through an origami inspired folding pattern. It aims to emulate the diffuse, dappled light quality created by deciduous trees in the summertime by smoothly responding to daylighting conditions.

The specific folding pattern is developed in the sense of its geometric efficiency for its folding mechanism. This frees the burden of complex construction and maintenance of mechanical dynamic façades, while it allows diffused shading with millimeter scale panel folds, just like sunshine through leaves. This scale factor can also specifically respond to the problem of glare. The module size can be very small and ZEAF’s shrinking capability in both directions also maximizes the diffusing quality. Lastly, this method can be applied to the mass production of dynamic façade systems with relatively inexpensive material cost and a high degree of design flexibility.

Another outcome of this project is the development of light-responsive polymer, which can be used for other applications such as light-responsive membranes with robust antifouling properties for water purification.  The detailed design of ZEAF prototype was developed and the folding pattern analyzed and simulated for the optimal open close system as shading application. We learned that the folding mechanism based on Miura-ori is promising for the application of responsive building envelope. We fabricated the folding module using Shape-memory polymers to confirm the concept. We also researched and fabricated light responsive polymer sheet based on azobenzene-containing materials. We learned that the current azobenzene-containing materials do not provide enough folding movement. The volume change of the synthesized material is less than 3% in response to the light. Therefore, we decided to apply the principle of ZEAF and the folding pattern to the similar open close mechanism using the store strain energy of the metal band with different scale. We fabricated the folding membrane between the elastic bands. The design has won the first prize at an international design competition, acepted to international conferences for archtiects and engineers.

The light-responsive materials have been used to design light-responsive membranes with superior antifouling properties for water purification.  Stimuli-responsive membranes have been widely explored to mitigate fouling on the membrane surface to achieve stable performance of water purification. In this work, we demonstrate a facile one-step coating of photo-mobile materials on membrane surface to impart self-cleaning property upon exposure alternatively to ultraviolet (UV) and visible light. Specifically, we successfully co-deposited photo-mobile 4,4’-azodianiline (AZO) and a bio-adhesive polydopamine (PDA) on the surface of ultrafiltration (UF) membranes. The effect of the coating layer on the surface hydrophilicity and pure water permeance was systematically evaluated. The photoresponsive properties of AZO in solutions and thin films with PDA was characterized using UV-Vis absorption spectroscopy. When shed with UV light, AZO undergoes photoisomerization from trans-AZO to cis-AZO, increasing surface hydrophilicity and decreasing the volume, while the exposure to visible light enables the transition from the cis- to trans- configuration. The resulted self-cleaning behavior of the modified membranes is demonstrated in treating 1 g/L bovine serum albumin (BSA) solution. For example, the self-cleaning of UF membranes increased water flux by ~160% when the membranes were challenged with the BSA solution.