Buildings are responsible for nearly half of all the carbon emissions in the developed world and play a key role in climate mitigation. Yet we know that despite all good intentions, new buildings use four times the amount of energy they are predicted to use. Why is this? For decades there has been a desperate lack of evidence about how well our buildings perform because so little evaluation has been undertaken of buildings in use. Today, the field of occupancy evaluation and feedback is rapidly expanding to address this need which is now a legal requirement. This book sets out a theoretical approach to the field based on the authors combined experience of carrying out occupancy feedback on a variety of buildings for the last ten years. It goes beyond the usual case study approach to examine the key concepts which underlie occupancy feedback, drawing on a range of disciplines including building science, ethnography, design, management and human behaviour. It situates the theory of occupancy feedback firmly within the critical agenda of climate change mitigation and provides insight into a number of new techniques which the authors have developed to address this field. For the first time, occupancy feedback in housing is presented as a rapidly developing area within the field including the latest research by the authors providing new ways of thinking about users and housing performance. The need for training and education in relation to occupancy feedback is also tackled for the first time. The authors' long experience of teaching occupancy feedback to others is encapsulated in a concise, easy to read primer which sets out their approach and provides a ready reference for clients, policy-makers, practitioners, academics and students alike to use.