Increasing the density of a city from within, as an alternative to urban sprawl, is the dictate of the hour, and not just for environmental reasons. Urban life has acquired a new value in all age groups and for all lifestyles. As a result, inner-city areas are undergoing a process of revitalization, with the development of wasteland and the restructuring of commercial property to create more dwelling space. At the same time, big efforts are being made to retain and refurbish the existing fabric. For the extensions and additional storeys that are going up, flat roofs offer great scope, of course. The aim of any measures to compact the urban fabric and increase density is not just the provision of additional space, however, but the improvement of environmental conditions.