The article presents a new approach in which the Analysis Of Variance (ANOVA) is used to identify the design variables that have the most impact on the variation of the building energy performance for a typical office building and to allocate the contribution of each variable to this variation. Moreover, the study addresses an important issue concerning the identification and the setting of a set of simple and concise variables that can be used during the conceptual design stage of office buildings. The analysis shows that the suggested approach could be useful for architects to evaluate the degree to which each design variable contributes to the variability of the building energy performance. Besides, the results may be helpful to support policymakers during the elaboration of energy codes by providing adequate information for the selection and handling of the parameters that control the variability of the energy needs. (C) 2010 Elsevier Ltd. All rights reserved.