Energy in the urban environment: the role of energy use and energy efficiency in buildings

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A century ago, the world had many cities of which the greatest were magnificent centers of culture and commerce. However, even in the most industrialized countries at the time, only a tiny fraction of the people lived in these cities. Most people lived in rural areas, in small towns, in villages, and on farms. Visits to a great city were, for most of the population, uncommon events often of great fascination. The world has changed dramatically in the intervening years. Now most of the industrial world lives in urban areas in close proximity to large cities. Industry is often located in these vast urban areas. As the urbanized zones grow in extent, they begin to approach one another, as on the East Coast of the United States. The phenomenon of urbanization has moved to developing countries as well. There has been a flood of migrants who have left impoverished rural areas to seek economic opportunities in urban areas throughout the developing world. This movement from the countryside to cities has changed the entire landscape and economies of developing nations. Importantly, the growth of cities places very great demands on infrastructure. Transportation systems are needed to assure that a concentrated population can receive food from the countryside without fail. They are needed to assure personal and work-related travel. Water supplies must be created, water must be purified and maintained pure, and this water must be made available to a large population. Medical services--and a host of other vital services--must be provided to the population. Energy is a vital underpinning of all these activities, and must be supplied to the city in large quantities. Energy is, in many ways, the enabler of all the other services on which the maintenance of urban life depends. In this paper, we will discuss the evolution of energy use in residential and commercial buildings. This topic goes beyond urban energy use, as buildings exist in both urban and non-urban areas. The topic does not address all energy use in cities--urban transportation is clearly important. However, buildings are the largest energy consumer in cities by a wide margin. (A typical Western home will consume at least five times as much energy as the typical car that services it.) As we note later, buildings consume more than one-third of total commercial energy globally. In developing countries, a large portion of energy use in buildings is in urban areas even though there are still large populations in rural areas. This is because vast quantities of non-commercial energy--residue from plants, farm products, forests and dung from animals--are used to provide the services needed in households (primarily cooking and water heating) in many rural areas. Most of industrial energy use (which accounts for slightly more than 40 percent of global energy use) is outside of urban areas. Thus, any effort to address energy use in urban areas needs necessarily to deal with the energy use in buildings.