A holistic model for analyzing energy benefits of urban density by relating energy use, building height, and overall city structure

More than half of the world population live in cities, and the urban population is further expected to almost double within 2050. This opens a rare window of time for realizing energy savings through overall city planning. How the overall city structure influence energy consumption is, however, still poorly understood. A central theme in the sustainable development of urban form is the compact city, and as a key instrument of this densification, tall buildings may prove important. Yet, the overall energy-saving potential of building taller and denser remain largely unclear. Moreover, current studies are described as far from holistic, not capturing the interconnectedness and complexity of the system as a whole. They are mostly qualitative, and methods depend largely on context. There is thus a lack of a clear theoretical framework for understanding energy consumption at the urban scale. The ambition of this thesis is to address this knowledge gap. This thesis develops a holistic optimization model for investigating the extent to which urban density and urban structure influence the energy consumption of the urban system. Energy aspects in land use planning, including the influence of building height, are addressed. The model relates energy costs of building heights of three stories and greater, with transportation and infrastructure energy benefits of building denser. Multiple scenarios of differing climate, population, and other variables have been simulated. Only factors considered to be correlated with urban density are taken into account. Of these, solar irradiation and the urban heat island effect have been left out due to their complex nature. A denser and taller city structure than what is normal in cities today is found to be optimal for low urban energy use. The most influential urban density indicators are embodied energy (most heavily influenced by building lifetime) and floor area per capita. The findings of the research indicate that building heights approximately in the range 7-27 stories are optimal for a given population and building lifetime. For buildings taller than this the increased embodied energy outweighs further reduction potentials of other elements. Energy use per capita in a city with optimal density is increasing slightly with population. Transportation energy is found to be much less important than building energy, especially in dense small area scenarios, but becomes increasingly important for low-density scenarios with large