Exterior Cladding System
In OSIRYS, the external cladding system is designed not only to provide a skin or layer intended to control the infiltration of weather elements, but also for aesthetic purposes.
The multilayer façade is divided into three components; a) multilayer module part (or core wall), b) an exterior finishing panel and c) an interior finishing module.
The interior finishing is the solution proposed for the interior part of the multilayer façade. It combines lightweight bio-materials and an active coating, which combined in a single unit will bring significant benefits on healthier indoor environment, thermal and acoustic performance compared to existing alternatives.
The multilayer module or the core wall of the envelope, which is a combination of different materials developed in the project, provides the acoustic and thermal protection, but also the fire resistance and the structural resistance to the whole system. A combination of bio foams (VTT), cork (Amorim), FR cork-thermoplastic sheets (Conenor) and pultruded profiles (Omikron) developed within OSIRYS has been used for these elements.
The exterior finishing panel is made of natural fibre (jute twill 2×2) and bioepoxy resin and has been manufactured through resin vacuum infusion by ACCIONA. These panels have a 3D curved surface (UNStudio) and are 4.3 m long by 1 m width both things are very challenging from a manufacturing point of view. Different combinations of natural fabrics and bio-resins have been tested and the combination that better meet the design requirements, from both, a mechanical and processing point of view was selected for the demo buildings.
TECNALIA has carried out mechanical analysis by Finite Element Analysis (FEA) to evaluate the estimated stresses and deformations produced by mechanical loads in the multilayer façade. The results will validate the designs according the failure criteria defined in European construction standards. These simulations showed a requirement to use some ‘ribs’ at certain points of the length of the panel as reinforcements. These ribs are used to stiffen the panel in order to avoid excessive deformations when it is subjected to different loads. The rib consists in a core of recyclable fire retardant PET foam covered by flax fibre that creates the union with the rest of the part. Figure 3 shows the final appearance of the reinforcement solution, one covered only with glass fibre and in the other one using jute fibre.
Another challenging point from a manufacturing point of view is to obtain 90° angles on the panel flanges. Previously manufactured countermoulds with well-defined angles are placed between the first and the second layer of dry fabrics in order to avoid wrinkles, air gaps and resin excess in the final parts which gives the desired result (Figure 4). It will contribute to a fast installation because it eliminates the need for a vertical set joint and the large sheets give fast wall coverage.
ACCIONA has demonstrated that is feasible to manufacture these complex biocomposite thermosetting panels (Figures 5 and 6) by resin infusion. The figures below show the mould and the curved panel from different perspectives once it was demoulded.