With the built environment contributing 40% to total global greenhouse gas emissions and with 87% of the buildings we will have in 2050 being built already, we urgently need to adapt existing stock sustainably - if predicted climate changes are correct. The notion of retrofitting existing cities has gained increasing prominence within research and policy agendas in recent years. Local government authorities are encouraging building adaptation in order to lower their building related energy consumption and associated greenhouse gas emissions. In most developed countries we now spend more on building adaptation than we do on new construction. Reuse is an inherently sustainable option, which reduces the amount of waste going to landfill. Inevitably, urban settlements and areas undergo change, whereby land uses become obsolete and buildings become vacant. At this stage in the lifecycle, the options are either to demolish or to convert the building to another use. In some city centres, such as London and Amsterdam, there is a long history of office-to-residential conversion, whereas in other cities these types of conversions are few in number. However things are starting to change and a world-wide trend is emerging in conversion. This research book investigates the nature and extent of the phenomena in a number of global cities, as well as the political, economic, social, technological, environmental and legal drivers and barriers to successful conversion. Through international comparisons with cases in the UK, US, Australia and the Netherlands, the book identifies the key lessons. There is substantial potential to change the nature of cities with residential conversion of office space and to build resilience for climate change. This book explores this potential. The opening and concluding chapters set out a framework for a more holistic approach to assessing the multiple benefits and issues surrounding the sustainable conversion adaptation decision. Each chapter covers a specific benefit and aspect of sustainable conversion adaptation through the whole lifecycle from inception and planning, design, procurement to construction, and management and operational issues. Chapters illustrate, and where possible, quantifies; through empirical research, the changes that have been achieved or delivered in sustainable conversion adaptation. The book is intended for researchers and academics for teaching purposes and to inform policy in urban design and in planning. It gives an overview of all aspects of performance characteristics and the conversion adaptation of existing buildings. It enables better informed decisions about whether conversion adaptation is a good choice and if so; which type of sustainability measures are best suited for projects - with empirical evidence to support that decision.