Environmental impact of building materials

Methods used for assessing the environmental impact of products comprise "life-cycle assessments" (LCAs) designed to provide information on all the significant environmental effects of products from raw-material extraction and manufacture to end-use and final disposal. The environmental impact of a product is often expressed in terms of an environmental "profile" indicating how the product contributes to changes in the environment, such as global warming or acidification. Research into the environmental impact of building materials and the methods for its evaluation has been carried out at VTT Building Technology Institute. This report discusses the principles and problems of LCA and suggests guidelines for evaluating the environmental impact of building materials. The guidelines are based on the LCA procedure suggested by SETAC. At least the following can be identified as special characteristics or problems in the LCA of building materials: Service life is usually long compared with ordinary consumer goods. The basic materials of building products such as rocky and clay materials, timber and gypsum are largely available. More important than the consumed materials is the means of removal and disposal. A considerable percentage of raw materials can be substituted by waste or co-products. At the same time, large amounts of co-products or re-usable waste of low value are generated in the course of production compared with the quantity of primary product. Thus the principles of allocating environmental burdens significantly affect the results of LCA. Selection of a well-defined functional unit in a building is complicated. Environmental impacts of wooden structural parts in house constructions were studied as a pattern. The environmental profile was calculated and compared with that of heating a small house. Structural timber, roof truss and cladding boards were studied separately. The effects of system boundary and limitations on the results were investigated. The dominate parts in the life span of wooden products were discussed from an environmental point of view.