It is widely accepted that decisions taken during the early phases of building design have a large impact on the actual performance during the lifetime of the building. The aim of this research is to explore the prospect of developing thermally robust outline design by incorporating sensitivity analysis in the design process. The work has been done by examining the sensitivity of energy performance of school building schemes which are still at an early stage of the building design process. In order to reveal the sensitivity difference towards climatic conditions, the analysis has been performed for four degree day regions of Turkey. A representative classroom block has been modelled by a dynamic simulation program and the input parameters were determined. The analysis has been carried out from the point of view of energy consumptions. The consequence of the research includes an attempt to develop a new, more thermally robust outline design concept, which is significantly more robust than the current general scheme. In order to test it, three pre-design alternatives were applied to different climatic regions to allow validation of the outcomes proposed in this study.