Climate change poses a significant challenge to the energy efficiency of buildings in Italy. This study examines the effects of climate change on energy performance, focusing on the influence of building shape (S/V ratio) and window total solar energy transmittance (ggl,n). Using a five-step methodology, the study explores three representative concentration pathways for the years 2030, 2050, and 2070, as shown in Fig. 1. Key findings reveal that rising temperatures will decrease heating demand, but significantly increase cooling needs, particularly in southern Italy. The study emphasizes the significance of building shape, showing that lower surface-to-volume (S/V) ratios lead to reduced energy consumption across different climates. For Lecce, buildings with an S/V ratio of 0.35 show EPtot,nd values ranging from 40.01 to 31.11 kWh/m2 depending on the regulation and year, whereas an S/V ratio of 0.75 results in values between 99.12 and 81.59 kWh/m2: compact buildings showed notable efficiency improvements compared to less efficient shapes. The effect of ggl,n on energy efficiency is evident: windows with lower ggl,n values improve cooling efficiency in warmer climates. The research focuses on updating regulations to include climate projections, promoting compact designs and optimized windows. It recommends a comprehensive approach that integrates thermal transmittance, S/V ratio, and glazing properties for climate-resilient buildings.