Energy efficiency in buildings has become a key goal of any energy policy. Europe relies on the Energy Performance of Buildings Directive (EPBD), which has been converted by Flanders into the 'Energy Performance and Interior Climate (EPB). Taking into account this Flemish EPB-standard (in terms of maximum U-values, E-level and K-value), this study seeks the economically most profitable combination of insulation facade, roof, floor and glazing for the Flemish citizen. For this purpose, a scenario-analysis is conducted using the EPB-software Flanders and a self-designed Excel file. Based on some important profitability criteria, the most profitable combination is determined for three representative types of dwellings studied. The scenario-analysis generates some well-founded guidelines for the Flemish citizen when building a house. It shows that in order to ensure the maximum profitability from investment in insulation, the key factor for the semi-detached dwelling is the insulation of roof and floor, whereas for a detached dwelling the key factor is the insulation of facade and floor. As a subsidiary consideration, the study also indicates that the U-values resulting from the more stringent E-level are still not sufficiently stringent because the U-values obtained for the most profitable combination are far below their maximum value. The same consideration applies in the case of the K-value. (C) 2010 Elsevier Ltd. All rights reserved.