Thermal Performance and Energy Efficiency of Lightweight Steel Buildings: a Case-Study

Steel façade systems follow the actual tendencies in construction offering robust and sustainable solutions, able to answer to actual conditions and to offer adequate interior thermal comfort. The modern sandwich panels provided by the current façade system producers combine the required thermal resistance by varying the thermal insulation material and its thickness with the required structural demands. In addition, the façade layer could be over-coated with different materials, thus offering the required architectural aspect. Other advantages of the systems rely on industrialized prefabrication, fast installation and adaptability. They could also be disassembled and reused. The study presents an analysis of some envelope solutions existing on the market for buildings made of thin-walled cold-formed steel structural systems. The study consists in an annual energetic analysis of Mineral Wool (MW)-based system and a more sustainable recycled-PET thermal wadding-system. The analysis includes for input the own-produced energy by power grids and additional national grid energy while for output heating / cooling and electric appliances are considered. The study is completed by a life-cycle environmental analysis. The study revealed that when the thermal insulations have nearly the same U-value, the environmental impact of the recycled-PET thermal wadding-based system is smaller than that of MW-based system. Although the environmental impact of the recycled-PET thermal wadding is higher in the production stage, the insulation quantity of the material needed for PET-recycled thermal wadding to accomplish the required thermal resistance is much smaller than that of MW. Moreover, the original material for the recycled-PET thermal wadding is 100% recycled which implies a certain benefit of circularity to the material. The study also proves that the glazing ratio has also an impact on the thermal performances of studied systems: by reducing the overall glazing ratio of the envelope, the solar gain drops significantly, which leads to an increased heating energy demand, in order to meet indoor thermal comfort.