Technological refurbishment and energy retrofit of large, flat roofs by using metal sheet systems: the case study of a multifunctional building

Flat roofs in architecture are particularly suitable for large buildings such as factories, warehouses, or exhibition halls. Metal sheet roofing systems generally allow to reach slope pitches down to 1%, without compromising the global water-tightness. However, since achieving such performance requires an accurate and experienced design to guarantee a full integrity over the years, the actual roofs service-life is, in often cases, significantly reduced to a much shorter period than expected, possibly leading to the need of a substantial refurbishment to definitively solve problems mostly related to water seepage. Considering the need for refurbishment of a large part of the industrial building heritage, such circumstances can be an opportunity to pursue an energy refurbishment by the improvement of the thermal/hygrothermal performance of the roof and, eventually, also the integration of photovoltaic panels. While waterproofing membranes might be not the most appropriate solution (considering roof dimensions and complex geometry), standing seam roofing systems are a versatile solution which is particularly suitable for large, flat roofs, as they fully comply with the lightweightness requirement typical of large-span structures, guaranteeing an adequate load bearing capacity and wind resistance at the same time. The paper investigates a significant case study of an energy and technology retrofit of a large, flat roof covered with a standing seam system, eventually integrated with a large-scale solar power plant. In particular it examines the previous pathologies occurred and discuss the design of the new roof layouts, slopes pitch, and construction details, also showing the experimental tests conducted to better define the best design solution.