Densifying cities could cut emissions more than doing energy retrofits on buildings.

Densifying cities could cut emissions more than doing energy retrofits on buildings.

That’s according to a new study published in Proceedings of the National Academy of Sciences.

You’re probably used to hearing about how denser cities cut transportation emissions, thanks to reduced driving. This study looks at a different impact: how density affects greenhouse gas emissions from buildings.

The researchers projected emissions from buildings under different potential urban densities between now and 2050. They found that denser development patterns lead to lower emissions because people live and work in smaller units that consume less energy. Attached buildings are also more efficient for heating and cooling.

So the PNAS study finds that greater density has the potential to substantially reduce building emissions, more so than other efforts to improve energy efficiency like better weather-proofing.

Unfortunately, global trends are moving in the wrong direction. Cities around the world are growing, but at the same time, urban density is decreasing, as cars enable cities and their suburbs to sprawl outwards.

Governments can adopt policies to make their cities and towns denser, and they’ll need to — not just in the relatively sprawling cities of North America and Europe, but in the fast-growing cities of Asia and the rest of the developing world.

Jan 19, 2017
Although the scale of impending urbanization is well-acknowledged, we have a limited understanding of how urban forms will change and what their impact will be on building energy use. Using both top-down and bottom-up approaches and scenarios, we examine building energy use for heating and cooling. Globally, the energy use for heating and cooling by the middle of the century will be between 45 and 59 exajoules per year (corresponding to an increase of 7–40% since 2010). Most of this variability is due to the uncertainty in future urban densities of rapidly growing cities in Asia and particularly China. Dense urban development leads to less urban energy use overall. Waiting to retrofit the existing built environment until markets are ready in about 5 years to widely deploy the most advanced renovation technologies leads to more savings in building energy use. Potential for savings in energy use is greatest in China when coupled with efficiency gains. Advanced efficiency makes the least difference compared with the business-as-usual scenario in South Asia and Sub-Saharan Africa but significantly contributes to energy savings in North America and Europe. Systemic efforts that focus on both urban form, of which urban density is an indicator, and energy-efficient technologies, but that also account for potential co-benefits and trade-offs with human well-being can contribute to both local and global sustainability. Particularly in growing cities in the developing world, such efforts can improve the well-being of billions of urban residents and contribute to mitigating climate change by reducing energy use in urban areas.

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