Proposal of a method for allocation in building-related environmental LCA based on economic parameters

Application and development of the LCA methodology to the context of the bu ilding sector makes several building specific considerations necessary, as some key characteristics of products in the building sector differ consider ably from those of other industrial sectors. The largest difference is that the service life of a building can stretch over centuries, rather than dec ades or years as seen for consumer products. The result of the long service life is that it is difficult to obtain accurate data and to make relevant assumptions about future conditions regarding, for example, recycling. Thes e problems have implications on the issue of allocation in the building sec tor, in the way that several allocation procedures ascribe environmental lo ads to users of recycled or reused products and materials in the future whi ch are unknown today. The long service life for buildings, building materia ls and building components, is associated with the introduced concept of a virtual parallel time perspective proposed here, which basically substitute s historical and future processes and values with current data. Further, th e production and refining of raw material as a parallel to upgrading of rec ycled material, normally contains several intermediate products. A suggesti on is given for how to determine the comparability of intermediate material s The suggested method for allocation presented is based on three basic ass umptions: (1) If environmental loads are to be allocated to a succeeding pr oduct life cycle, the studied actual life cycle has to take responsibility for upgrading of the residual material into secondary resources. (2) Materi al characteristics and design of products are important factors to estimate the recyclable amount of the material. Therefore, a design factor is sugge sted using information for inherent material properties combined with infor mation of the product context at the building level. (3) The quality reduct ion between the materials in two following product life cycles is indicated as the ratio between the market value for the material in the products. Th e presented method can be a good alternative for handling the problem of op en-loop recycling allocation in the context of the building sector if a con sensus for the use of the fictive parallel time perspective and the use of the design factor can be established. This as the use of the time perspecti ve and design factor is crucial to be able to deal with the problem of long service lives for buildings and building materials and the specific charac teristics of the same building materials and components built into differen t building contexts.