The assessment of environmental performances of building is now commonly based on a life cycle approach. The current studies comparing such performances highlight the problems related to uncertainties in the Life Cycle Assessment (LCA) results. The aim of this study is to identify the sensitivity and robustness of LCA models to uncertainties related to building materials in order to strengthen comparisons which can be done between building projects and secure the assessment of the building environmental performance calculation. However, in this study, all uncertainties are not covered and we restricted our calculation to uncertainties related to the use of building materials during the life cycle of the whole building. We have considered that the relative contribution of each material to the environmental impact of building is sensitive to three key points which are submitted to uncertainties: the service life of the building component; the environmental impact of this building component's production and the amount of material used in the building. The assessments of the uncertainties are treated at two levels: the material or element level and the building level. A statistical method, based on Taylor series expansion is developed to identify the most sensitive and uncertain parameters, with standpoint to strengthen comparison between projects. The first results are promising, although further work remains to be done to better quantify the uncertainties at the material scale. © 2013 Elsevier Ltd. All rights reserved.