At the same time, their proposal does not forgo energy efficiency and sustainability. On the one hand, the design of the Use-Neutral Towers generally relies on cylindrical shapes. According to lead designer Matthias Olt of B+H Architects, “a ring or tube is the most efficient form of construction in terms of materials and structure”. In addition, the circular shapes favour modularity, as they can be easily reproduced, rotated and positioned in different configurations. Also, modularity allows for prefabrication. In addition, towers can be built with timber, if 18 storeys or less, and with a combination of timber, concrete and steel for towers above 18 storeys. Modularity, prefabrication and timber, as we have seen in some of the articles published in these pages, contribute positively to energy efficiency and to faster, cheaper and less polluting construction.