New thinking is essential if we are to design and occupy buildings that can keep us safe with unpredictable economies, climates, energy systems and resource challenges. For too long designers have relied on mechanical solutions for heating, cooling and ventilating buildings. The 21st century dream has to be of a better architecture that enables buildings to be run for as much of a day or year as possible on local, clean, reliable, affordable natural energy. Examples are included from different climates where the fundamental building design is right, its orientation, opening sizes, mass and its natural ventilation systems and pathways. Many modern buildings are poorly designed for climate as manifested by growing incidences of overheating experienced indoor, explored here. The inability of many rating systems to record and improve the climatic design of buildings raises questions about how they deal with issues of basic building performance. This books points the way towards how we can understand such problems, and move forward from over-mechanised poorly designed buildings to a new generation of adaptable buildings designed and refurbished to run largely on natural energy and capable of evolving over time to keep their occupants safe and comfortable, even in a warming world. The chapters were originally published in Architectural Science Review.