Urban renewal applicable to an increase in density: Conceptualization of compact-KDT in Vietnam with Hanoi as a case study

Urban renewal projects are becoming more and more active, especially in public-owned gold land plots in Vietnam's cities center. The re-development of these land resources known as the residentialization: transformation of different land-use functions into new residential areas (also new neighborhoods) - the KDTM ({Khu Do Thi Moi} abbreviated in Vietnamese) - is increasing the urban density in these areas. Vietnam uses three factors to control urban density: building density; number of floors and/or height of the building; floor area ratio. The current tasks of land-use policies are the determination of an urban density that can adapt to the development of urban space; take full advantage of the land value increment, boost investments without causing any consequences because of the overcrowded population. The residential units will be called compact units when their (occupancy) density exceeds the threshold of 300 persons/ha. For the Compact-KDT concept (compacted KDTM), it is recommended to have: (1) the average level of compactness corresponding to the density of 300 to 600 persons/ha; (2a) the high level of compactness to be controlled - 600 to 1200 persons/ha; (2b) the high level of compactness to be strictly controlled and applied in some exceptional cases - 1200 to 2000 persons/ha; (3) the extremely high level of compactness to be avoided - more than 2000 persons/ha. A Compact-KDT always guarantees the functions of a "normal" KDTM, there are some functionalities that should be added: organization of land-use and spatial functions; public spaces; internal traffic; and reducing energy consumption and the use of non-recyclable natural resources. Rather than being passive to fluctuations in urban density, this increase can be accommodated with a calm and fair attitude by analyzing adverse consequences and the benefits of this process, not just negative effects for the development of urban space, the concentration of population and the economic growth of cities. Keywords: urban renewal; urban density; new urban areas/new residential areas (KDTM - Khu Do Thi Moi); residentialization; (new) compact urban areas (Compacted KDTM/Compact-KDT).