Application of life cycle assessment in urban projects

International audienceSustainability is now targeted in nearly all urban projects, but LCA is generally seen as too complex so that more qualitative approaches are generally preferred. Indeed the importance of environmental problems regarding e.g. climate change, human health, biodiversity and resource depletion should justify a more precise decision making process. This communication presents some tools being developed these last ten years and several applications showing that new computer techniques allow LCA to be applied on a larger scale than just one building. Numerous models have been developed since the 80's to evaluate environmental impacts of one building using LCA, but decisions made at the level of a settlement have important consequences on the energy and environmental performance of buildings. Bioclimatic architecture depends on the outline of the streets: for instance organizing terraced houses with a proper orientation decreases the heating load compared to standard detached houses. Also, collective equipment like district heating and public transport can be more efficient than individual systems. Settlement models are therefore useful to complement building models. A life cycle simulation tool has been developed to model urban projects including various buildings, streets, green and other public spaces, and networks (drinking water, waste water, district heating...). This tool, developed in an object oriented approach, associates dynamic thermal simulation and building LCA, complemented with modules for open spaces and networks. A set of environmental indicators is evaluated, e.g. resource depletion, energy and water consumption, global warming, waste generation, toxicity. Several alternatives can be compared, constituting an urban design aid. This communication presents a case study illustrating a possible application of this tool. Several urban morphologies are compared including residential and tertiary buildings, according to passive or Plus energy concepts. Each alternative is defined according to the same functional unit corresponding to a number of inhabitant and employees during 80 years, in the Greater Paris Area context and climatic conditions. The results are presented showing e.g. the contribution of buildings and transport in the overall environmental balance. Perspectives are proposed to refine the model and complement it, regarding e.g. dynamic and consequential LCA. • Maximal length: 2500 characters including space