This book discusses nocturnal cooling technologies for building applications. Exploiting the natural environment as a renewable and sustainable resource has become a significant strategy for passive energy saving in buildings, and has led to growing interest in the use of passive radiative cooling based on nighttime (nocturnal) and daytime (diurnal) operating periods. Of these, nocturnal cooling is more promising since diurnal cooling is hard to achieve due to the solar radiation effect. As such, this book provides a comprehensive overview of nocturnal cooling for building applications, including a definition, concepts and principles; materials and devices; and cooling systems and configurations.