Exploitation of shape memory materials in sun adaptive user-controllable building façades

Smart morphing materials are increasingly studied and are also expected to soon become economically available for architects and engineers, being potentially suitable for a great number of applications. In particular, shape memory materials possess the unique feature of memorizing shapes that can be continuously recovered through the application of external stimuli. This research proves the potentialities of an adaptive shading module actuated by smart materials, which enable the facade shape to change in response to the incoming solar radiation. The final goal is to design a building skin that is attuned to climatic changes and which creates occupants’ awareness of environmental variation. In particular, the exploitation of the physical properties of shape memory materials would guarantee the internal daylight comfort with (almost) zero-energy actuation and reduced system complexity; this would be in contrast with kinetic envelopes which, in order to preserve interior conditions in response to external variations, rely on sensors, motors, and computational feedback loops. Inspired by nature and mimicking petals’ movement dynamics, the proposed facade module has been designed starting from a geometrical schematization of flower’s shape: four triangular petals on a square basis dynamically adapt their degree of openness based on the incoming solar radiation. The petal-like wings, actuated by strips of a two-way shape memory polymer, allow a completely autonomous passive control of building interiors’ conditions and zero-energy actuation. The actuator is located on each petal side directly exposed to solar irradiation, triggering the shape transition: activation is started by solar absorption, which increases the polymer film temperature until the transition condition in attained. Moreover, the integration and addition of a matched internal opaque layer, actuated by a set of (electrically controlled) antagonistic shape memory alloy torsion springs, grants the possible implementation of the resulting structure in real buildings, conciliating comfort, well-being and user controllability of living and working environments. Dynamic daylight simulations have been carried out to assess the effects of the resulting shading system on a medium size office room oriented towards South-East, during the most illustrative days of the year. The movement of the external autonomous shading layer has been discretized into four different positions, from a completely open to a fully closed one. The daylight quality was assessed by computing two different performance indices: the work plane illuminance and the degree of glare probability (Dubois, 2016).