In some cities, solving the problem of urban sprawl could cut carbon emissions in buildings more than retrofitting those buildings with the latest energy-efficient technology.
Around the world, according to a new study, cities are on track to become less dense and more sprawling over the next few decades. This is a problem: apart from contributing to air pollution by privileging car culture and encroaching on wildlife habitats, sprawl, according to the study, results in buildings that use way more energy than more tightly-packed urban structures. But if cities can start planning for denser future layouts now, they could significantly curb how much energy their buildings use.
The study looked at different scenarios for both density and energy-saving technology, and how both can help save energy used in heating and cooling. With a combination of compact urban growth and the most advanced efficiency technology, energy used for heating and cooling might increase 7% by 2050. With more sprawl and without new technology, it could increase as much as 40%.
In developing countries, where cities are growing fastest, curbing sprawl actually makes more of a difference than efficiency upgrades. "Cities in developing countries are still in the making . . . most of their building stock in 2050 will have been built since 2010," says Burak Güneralp, an assistant professor of geography at Texas A&M University and lead author of the study, in an interview with Co.Exist. "For building energy use in these rapidly growing cities, how dense these new developments will be matters far more than improvements in energy efficient technologies."
Density helps buildings save energy in a few different ways, but the study looked at one simple reason: In a denser area, people are more likely to live in smaller apartments than bigger houses, and a small floor plan automatically takes less energy to heat and cool. (Solving sprawl also comes with multiple other benefits, including making citizens less fat and reducing traffic).
In North America and Europe, density also plays a role in energy use, but because cities in developed countries have older buildings, there's more opportunity to make a difference with energy retrofits.
In China, where hundreds of cities have been built over the last few decades—often filled with low-quality, inefficient buildings—energy retrofits are also important. As China continues to grow, and annual heating and cooling energy use increases as much as 50% by 2050, planning for density is also key.
But cities would have to start implementing density strategies now to really make an impact. "The energy performance of buildings can be improved through retrofitting, but it is much harder to change the layout of a neighborhood, let alone of an entire city, once it is in place," says Güneralp. "This locks in cities in terms of energy use, and hence carbon emissions."