The art of making things fit for use again goes back to the beginnings of human construction. In modernism's focus on progress and new constructions, this tradition was at best only marginally considered. Since then, the guiding principles for construction have undergone another radical shift. Sustainability, preservation and upgrading have become key concepts of the construction sector's retrofit turn, and the built heritage of the high modern era itself now requires structural and energy efficiency upgrades. From a variety of perspectives, this volume explores the specific challenges this poses for conservation and explores the sophisticated strategies and methods now available for close-to-reality assessment and retrofitting measures appropriate for the built heritage from the high modern times.