This book provides a methodological framework to set properly the thermal enhancement and energy efficiency in historical buildings during a renovation process. It describes the unique thermal features of historical properties, closely examining how the building materials, structural elements, and state of conservation can impact energy efficiency, including sample calculations and results. It also describes means and aims of several fundamental steps to improve energy efficiency in historical buildings with an experimentation on a case study. This timely text also introduces leading-edge technologies for enhancing the energy performance of historical buildings, including the potential for integration of co- ad tri-generation though micro-turbines, photovoltaics and solar collectors and their compatibility with architectural preservation.