Thermally Adaptive Building Coverings Inspired by Botanical Thermotropism

Abstract

This paper covers the new field of thermally adaptive building coverings, their inspiration, basic operational characteristics, analytical modeling and coupon testing. Inspiration for thermally adaptive building coverings come quite notably from various families of thermotropic plant structures. Certain plant cellular structures like those in Mimosa Pudica (Sensitive Plant), Rhododendron leaves or Albizia Julibrissin (Mimosa Tree), exhibit actuation physiology which depends on physical manipulation and/or thermal loading as a function of solar radiation. The paper draws parallels between the differential actuation via cellular turgor pressure manipulation. A parallel with these structures can be seen in the new field of thermally adaptive building coverings which use various forms of cellular foam to aid or enable actuation much in the same way that plant cells are used to move leaves. When exposed to high solar loading, the structures curve upwards and outwards. When cold, these same structures curve back towards the building forming convex pockets of dead air to insulate the building. The paper shows the basic classical laminated plate theory models comparing theory and experiment of such coupons. The study concludes with a basic description of the effectiveness of thermally adaptive building coverings.