This open access book gathers peer-reviewed contributions presented at the Building Digital Twin International Congress (BDTIC), held in Kaunas, Lithuania on May 14-15, 2025, as part of the SmartWins project. Focusing on digital twins to ensure the transition to a smart, sustainable, resilient and carbon neutral built environment, the contributions highlight the latest findings in this fast-growing field, addressing topics such integral components of smart buildings digitised assessment, indoor environmental quality assessment with smart sensors, IoT and digital twins for assessing the performance of smart buildings, and energy assessment of smart buildings in BIM environment.