LCA Based Comparative Evaluation of Building Envelope Systems

Issues about the evaluation of the environmental sustainability of products and industrial processes are slowly involving every industrial sector among which, building and construction sector. While National strategies are finally moving toward an agreement for the reduction of green-house gas emissions, in order to mitigate the global warming effects, buildings, which are also responsible for a significant share of non-renewable energy use, are not yet enough analyzed in every different life cycle phase: the discussion about the choice of environmental indicators to be considered [1], their computational methodology and the limits to be respected is still open. Life Cycle Assessment (LCA), fully defined in a series of International Standards for industrial products, seems to be the only holistic tool able to give an objective measure of the environmental impact of a building and, from it, its sustainability. Nevertheless, its application in the building sector is particularly difficult, due to the intrinsic complexity of the building itself: the variety of products it is made of, the many impacts it generates during its life cycle, the length of its life and the difficulty to forecast its use and maintenance during its service life and disposal or reuse opportunities after more than fifty years. Different models and approaches have been developed and carried out, in the two last decades, by several authors [2], to cope with this complexity and the literature review shows that there are still different opened critical issues for the identification of a valid methodology [3]. The aim of the paper is to make the point of the environmental assessment of building envelope subsystems and to pave the way for a LCA-based measure of the environmental performances of the design solutions and the evaluation of the sustainability propensity of building technologies in general, as a tool to support not only detail design choices but also strategic choices. A preliminary environmental comparison of one technology against another, in fact, can be used to take decisions in the very first phases and to compare life cycle impacts to life cycle costs and performances