© 2021 Elsevier B.V.Classification of climatic zones is required for building thermal regulation. In this context, a novel approach based on thermoeconomic analysis is proposed to reclassify climatic zones of Turkey. The classification is carried out by accounting different climatic-built parameters, namely thermal insulation, main wall component, fuel type, as well as heating and cooling degree-days (HDD and CDD). With this aim, 80 provinces of Turkey are reclassified into 5 zones based on fuzzy c-means clustering method regarding 27 different optimum insulation thickness attributes calculated for each city. The results showed that compared to the current national thermal zones, based only on HDD values, 16 out of 80 provinces shift to a new category, all of which correspond to a higher zone indicating the requirement of a thicker insulation layer. The results are presented with membership degrees giving more insight into the climate of analysed cities, discussed in terms of reduction in energy-cost and global greenhouse gas emissions. The obtained new classification revealed that the current national thermal zoning methodology is inadequate in division of the studied geographical area particularly for mild climates where cooling needs are significant. Finally, an updated climate zone map of Turkey for building thermal regulation is proposed.