Many new buildings are designed to be as energy efficient as possible and to use innovative technical systems for heating, cooling and lighting. But often these buildings do not meet their energy targets because the users of the building do not know how to use the systems, and behave in ways that actually increase energy use above that expected. This guide focuses on eight case studies of schools, offices and other new buildings in which the occupants' behaviour and its potential impact on energy efficiency were assessed. Numerous examples of design faults - for example, poorly labelled light switches, badly located temperature sensors, over-sensitive infra-red controls on sanitary fittings - were identified. Key recommendations are made for designers, facilities managers and building users, supported by detailed checklists on designing, managing and operating lighting, ventilation, temperature and water systems in order to ensure that buildings operate as efficiently as possible.