This book contains the proceedings of the 18th KES International Conference on Sustainability and Energy in Buildings 2026 (SEB 2026) held in Chania, Greece, during July 8–10, 2026, organized by KES International. The conference attracted submissions from around the world. Submissions for the full-paper track were subjected to a blind peer-reviewed process. Only the best of these were selected for presentation at the conference and publication in these proceedings. It is intended that this book provides a useful and informative snapshot of recent research developments in the important and vibrant area of sustainability in energy and buildings.