The trend towards green developments misses a clear definition of such concepts, though sustainability requires a more precise management of such important issues like climate change, exhaust of resources, pollution and waste. Life cycle assessment (LCA) constitutes a useful tool in order to help decision makers reducing environmental impacts by appropriate design. For instance the proposed concept of net energy producing building may lead to reduce the density of a city, thus increasing the need of transport. LCA could be applied in order to study a global balance and search for an adapted synthesis or optimization. Evaluating a set of indicators, LCA provides a more global assessment than a single criteria method like the ecological footprint or CO2 emissions. Its sensitivity to many parameters allows a decision aid to be provided to many actors like : municipalities and associated technical services, property developers, architects, contractors and users. This method is applied in many countries to study buildings, e.g. 8 tools have been compared in the European thematic network PRESCO. LCA has been applied in Germany to city districts, but for global studies and not as a design aid. The present project proposes therefore to develop an eco-design tool for urban settlements. The work programme includes the following phases. 1 Elaboration of specifications Experiences of green settlements will be analysed in order to review questions which could be answered using LCA, design parameters to be included, and relevant system boundaries according to the objective of the study. 2 Data collection Life cycle inventory data bases (concerning materials and processes) will be updated and complemented with e.g. the hourly variation of the electricity mix in France, emissions of recent wood fuel boilers, impacts related to the fabrication and end of life of PV systems etc. 3 Methodology and modelling A set of environmental indicators can be evaluated, but some aspects like the variation of the electricity mix are not accounted for. This leads to develop a dynamic LCA tool, which is innovative compared to the present methods where all parameters are fixed. This approach can also concern e.g. the variation of a boiler efficiency and thermal properties of insulation. 4 Software development The models developed in earlier phases will be implemented in a package including Pleiades-Comfie (thermal simulation), Equer (LCA of buildings) and Ariadne (LCA of urban settlements). The format of data from Geographic Information Systems will be examined in order to study the feasibility of linking such tools with LCA. 5 Application in case studies The tool will be applied to study : - an urban renovation project in Aubervilliers, North of Paris. The city is studying an environmental plan. Several scenarios will be compared using LCA, and the results will be used to help the municipality improving architectural and urban recommendations within this plan. - a green development project in the South of Paris A high environmental performance is targeted, and it would be interesting to express this performance using LCA indicators. These activities will be performed in link with European networks, e.g. the ENSLIC Building project regarding applications of LCA in the building sector.