Urban Shape & Ecoefficiency

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Thanks to Anthropocene for this summary of a counterintuitive finding:

To save energy on heating and cooling, look at the shape of cities, not just their buildings

Already, cities account for up to three-quarters of global energy consumption and fossil fuel-related carbon dioxide emissions. With 2.5 billion more urban residents expected by 2050, these proportions are set to increase even further. But scientists don’t know much about how the way cities evolve in different parts of the world may affect energy use…

…“In short, efficiency gains matter relatively more in those regions that are already highly urban,” the researchers write. That’s because where cities are well established, their general form—compact or sprawling—is already set.

Surprisingly, though, retrofitting buildings immediately doesn’t necessarily produce the greatest savings. Current technologies widely available for energy retrofits can save 20 to 40 percent of building energy use. But cutting-edge technologies could save 70 to 90 percent. Waiting five years or so for those new technologies to go mainstream and come down in cost could save more energy in the long term.

And the picture is different in rapidly urbanizing regions like China, South Asia, Pacific Asia, the Middle East, North Africa, and Sub-Saharan Africa. There, changes in urban density will have the biggest effect on building energy use.

Moreover, the pace of urbanization means that the next several decades will be key to determining the global energy budget over the long term. “Once in place, the physical structure of urban areas cannot be easily changed, and creates long-lasting interdependencies across land use, transport, and buildings that lock in the energy demand in these sectors,” the researchers warn. So urban policy wonks around the world take note: the time to develop compact, dense cities is now.

Source: Guneralp B et al. “Global scenarios of urban density and its impacts on building energy use through 2050.” Proceedings of the National Academy of Sciences2016.

Read the whole summary here.

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