A removable textile hybrid structural screen for the windows of Castello Sforzesco, Milan: when experimental metrics inform the bespoke ‘design-to-construction’ process in historical contexts

This paper presents the experimental design-to-installation process of two textile hybrid window screens, aimed at mitigating the comfort conditions and preserving the frescoes of Sala delle Asse at Castello Sforzesco, in Milan. Given the historical relevance of the context, the main challenges that the project tackles are: (1) implementing bespoke, low impact, lightweight structural screens as reversible additions to historical buildings; (2) enhancing the visual, lighting and hygrothermal comfort; (3) validating an interdisciplinary methodology from the performance-driven design to construction, with the aim to assess its replicability in other cultural heritage sites. The design task, led by Textile Architecture Network, at hand is to produce self-standing vertical screens for the large-scale windows, in order to control the sunlight amount on the frescos, as well as to block air drafts that cause humidity inside the room. The main challenge of the project proved to be the fragility of the context, since the screens must be sealed on the borders, whitout perforations on the vaulted edges. Thus, a textile hybrid structure is proposed, made of (1) form-active elements, due to its self-standing principle; (2) unconventional knitted textiles, that need to be characterized. Eventually, the paper presents the preliminary multidisciplinary research campaign consisting of (1) in situ anemometric tests by Experimental Mobile Laboratory; (1) material tests on optical transmittance by SeedLab; (3) mechanical tensile tests and the updating of material choices by Textile Architecture Network, all part of the Architecture, Built Environment and Construction Engineering Department’s Labs at Politecnico di Milano, Milan, Italy.