Density, form and performance

A redefinition of building economics towards sustainability will include the spatial approach of green field investments and most of all necessary intensification of brown field development. For large parts of Western Europe and the US the latter will be, according to economic principles of concentration and revaluation of city life, the main focus in development. Like the rest of the world, the growth of cities seems irreversible and a continuous fight against sprawl. Other studies reveal that sustainable economics require focus and insight on building characteristics. So density is the focal point. Urban quality can be partly quantified in parameters like Floor Space Index (FSI - intensity), Ground Space Index (GSI - compactness), Open Space Ratio (OSR - pressure on open space) and height. The density and the morphology of the urban fabric can be adequately described by these parameters, using plot charts where the different parameters are placed on the axis and the elements are plotted and analysed. The value of real estate property is determined by the building value and the land value. The building value is related to the location due to rent levels enabling building quality, urban quality and contextual (functional and economical quality). The land value should be almost equivalent to location value and, at least at the start of the process, is calculated using the looked-for Floor Space Index. It is expected that performance of real estate objects, categorised in different sets, defined by these urban parameters will show similar grouping, by which the density related behaviour can be forecasted. Used as a tool to analyse a portfolio it will give insight in the relation of this stock and density. This tool and gained insight is especially needed for emphasising externalities of density to a project scope. The central question “Why Tall?” can be answered by these regional advantages. At the same time urban planners, at least in Rotterdam, require tall buildings iconic by slenderness, an effect further stressed by regulation. This city is exemplary for a situation in which it is already hard to distinguish a need for going high. All externalities have to be taken into account. Even beyond economic viability, the fineness creates a setback on the performance by density. The original density plot charts are twodimensional. By adding colour the performance is shown and by using marker styles the impact of building volume related to the financial indicators can be clarified