Hygroskin - Meteorosensitive PavilionEdit profile
Climate-responsiveness in architecture is typically conceived as a technical function enabled by myriad mechanical and electronic sensing, actuating and regulating devices. In contrast to this superimposition of high-tech equipment on otherwise inert material, nature suggests a fundamentally different, no-tech strategy: In various biological systems the responsive capacity is quite literally ingrained in the material itself. This project employs similar design strategies of physically programming a responsive material system that requires neither extraneous mechanical or electronic controls, nor the supply of external energy. Here material computes form in unison with the environment.
The project explores the tension between an archetypical architectural volume, the box, and a deep, undulating skin imbedding clusters of intricate, climate responsive apertures. The pavilion’s envelope, which is at the same time load-bearing structure and metereosensitive skin, is computationally derived from the elastic bending behaviour of thin plywood sheets. The material’s inherent capacity to form conical surfaces is employed in combination with 7-axis robotic manufacturing processes to construct 28 geometrically unique components housing 1100 humidity responsive apertures.
The apertures respond to relative humidity changes within a range from 30% to 90%, which equals the humidity range from bright sunny to rainy weather in a moderate climate. In direct feedback with the local microclimate the pavilion constantly adjusts its degree of openness and porosity, modulating the light transmission and visual permeability of the envelope. This exchange results in constant fluctuations of enclosure, illumination and interiority of the internal space. The hygroscopic actuation of the surface provides for a unique convergence of environmental and spatial experience; the perception of the delicate, locally varied, and ever changing environmental dynamics is intensified through the subtle and silent movement of the meteorosensitive architectural skin. The changing surface embodies the capacity to sense, actuate and react, all within the material itself.
Nature has evolved a great variety of dynamic systems interacting with climatic influences. For architecture, one particularly interesting way is the moisture-driven movement that can be observed in spruce cones. Unlike other plant movements that are produced by active cell pressure changes, this movement takes place through a passive response to humidity changes. Therefore, it does not require any sensory system or motor function. The movement is independent from any metabolic function and hence, it does not consume any energy. Here, the responsive capacity is intrinsic to the material’s hygroscopic behaviour and its own anisotropic characteristics. Anisotropy denotes the directional dependence of a material’s characteristics. Hygroscopicity refers to a substance’s ability to take in moisture from the atmosphere when dry and yield moisture to the atmosphere when wet, thereby maintaining a moisture content in equilibrium with the surrounding relative humidity.
In this way, the movement of spruce cones is rooted in the material’s intrinsic capacity to interact with the external environment, and it shows how a structured tissue can passively respond to environmental stimuli: The cone opening (when dried) and closing (when wetted) is enabled by the bilayered structure of the scales’ material. The outer layer, consisting of parallel, long and densely packed thick-walled cells, hygroscopically reacts to an increase or decrease of relative humidity by expanding or contracting, while the inner layer remains relatively stable. The resultant differential dimensional change of the layers translates into a shape change of the scale, causing the cone’s scales to open or close.
description by the architects