Hygroscopic Coffer: Digital parametrization and realization of timber bilayer composites for passive dehumidification in built environments

Abstract

The integration between renewable materials and passive design strategies for the improvement of the built environment comfort leads to a reduction in energy consumptions and in the use of active HAVC systems. Sustainability concerns the materials employed, but also their performance: natural materials with embedded responsive properties respond to specific external stimuli, changing some of their physical or chemical properties and this represents an additional and innovative advantage in built environments. As biomimicry suggests, it is possible to take advantage of the embedded hygroscopic behavior of wood in order to create a hygromorphic composite material that passively reacts to relative humidity variations of the environment. These composites are realized with a cross-grained double-layered structure, joining a thicker veneer (active layer) and a thinner one (passive layer), in order to reproduce the principles that make pine cones scales bending after exposure to humidity variations.

The double-layered panels, called “unplywood”, can be digitally parametrized and used as a false ceiling for the passive dehumidification of an indoor environment, using only the convective motion of the humid air and the stack effect. This is particularly useful when the relative humidity excessively increases, exceeding the comfort levels.

The result is a passive dehumidification system where the timber panels act as sensors and as decorative architectural elements at the same time and contribute to improving the indoor environment from a hygrometric point of view as well as from a perceptive one.