LIGHTWEIGHT TRANSLUCENT FAÇADE

Spatial Timber Assemblies enables the fabrication of structures with a high stiffness in all directions with no requirement for additional reinforcement plates. DFAB HOUSE researchers used this liberty in material selection to develop an integrated high-tech façade solution. Instead of heavy timber plates a lightweight material with no capacity to take shear loads, specifically a transparent membrane, was chosen.

The main components of the lightweight translucent façade are aluminium profiles, membranes, translucent insulating material and cables that limit the deflection of the exterior membrane under wind suction and assist to withstand the forces generated between the two membranes. An important geometrical attribute regarding the load-bearing behaviour of the membrane system is its double surface curvature which is required to transfer external loads to the supports efficiently.

The cavity between the two membranes is filled with aerogel. This wall build-up exposes the interior spaces to natural light and ties them to the current external condition. Furthermore, using aerogel is the most efficient way to reach a lightweight system with ultra-high performance thermal insulation. While early developments of aerogel were restricted to niche applications in aerospace, the material has become commercially available in large amounts in the form of granules.

To enhance the façade’s thermal insulation without having to increase the wall thickness a novel material processing was developed to achieve a high packing density of aerogel particles. The new method takes advantage of the low stiffness of the employed high-performance transparent membranes. It involves cycles of first overfilling the cavity with aerogel granules, while simultaneously regulating the air pressure in the cavity to avoid reaching the plastic deformation of the membranes. Each cycle then has a step in which compressive loads are applied through the external post-tensioned cables, causing the desired irreversible densification of the granule bed. The combination of these strategies represents a generic approach that can be adapted to a broad range of lightweight translucent membrane façades.

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