Despite the large amount of existing research that has focused on the analysis of the uncertainties of environmental impacts of buildings, the improvement of its reliability still remains a problem. Current studies highlighted the influence of uncertainties in the minimization of effectiveness of life cycle assessment (LCA) method for decision making. With an aim of improving the reliability for strengthening the comparison of building projects, in this study, we propose a novel way of interpretation of environmental impacts. Coupling uncertainty and sensitivity analysis to the model for the evaluation of environmental impacts of buildings was possible to improve the robustness of project comparisons. Moreover, it is found that the contribution of uncertainties of inputs is not the same for different values of a building’s lifetime.