Life cycle assessment has been applied to buildings in order to evaluate and reduce environmental impacts in this sector, and many tools have been developed in order to provide assistance in the design process. But the application of this method on a larger system like an urban islet allows more aspects to be studied like global planning, mutual shading and shared equipment (e.g. district heating, compost system…). The work presented here focuses on the scale of an urban settlement, and aims to better understand the links between decisions and impacts. The objective is the development of a tool providing help in the design process of a settlement, by evaluating the impacts of the project. This will permit a comparison between design alternatives, and the study of some new concepts integrated in the settlement, like plus energy buildings.