This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book illustrates the theory of assessing multiple associations for each cost item to include the effect systems have on each other within a functioning building, thus illustrating the true impact of design choices as they would be in real life for living, breathing buildings taken as whole interactive systems rather than singular asset items. It describes the methods needed to take into account the effect on running costs of the physical interactions between all building aspects, from orientation and positioning to lighting, facade design and occupancy patterns. The book introduces whole life costs and its benefits along with a review of the different approaches used in the field. It also introduces the various “sustainable” options as incorporated in designs and provides details on how each of these affects other aspects of the building.