Compact Urbanization and Delayed Retrofitting Key to Future Urban Planning

Global urban population is expected to rise over 2 billion between 2010 and 2050 with these cities creating three-fourths of the world's fossil fuel-related CO2 emissions. As detailed in a paper co-authored by CEU's Diana Urge-Vorsatz and Mukesh Gupta and published today in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), it is vital for city planners and governments to consider how they build and retrofit existing structures for maximum sustainability and mitigation of climate change.

“Our scenario-based study provides a first-of-its-kind global analysis of future urban densities and their implications for building energy use. Developing effective strategies to adapt to and mitigate climate change in urban areas requires looking beyond aggregate statistics on population, physical extent and resource use,” the authors write. “Urban density, along with other determinants of urban form, determines local environmental conditions such as air quality, walkability, and access to green space, all of which have a bearing on the well-being of urban residents.”

The group's findings show that the most rapid projected increases in floor area are expecting in South Asia, increasing by 80 percent to 150 percent from 2010 to 2050. China's floor area will increase the most. The study shows that, with the exception of the Middle East and North Africa, almost all developing regions will increase floor size more than already developed regions. Although it sounds counterintuitive, they also concluded that retrofitting energy-inefficient buildings sooner than later does not necessarily lead to less building energy use in the future. This is because markets need some transition time to be able to deploy deep retrofits, saving high percentages in heating and cooling energy, on a mass scale, and semi-efficient retrofits only lock-in high energy use for decades.

“Waiting to retrofit buildings until the most energy-saving technologies are widely available will yield the most savings in long-term building energy use,” state the authors. Using state-of-the-art retrofit options – or so-called deep retrofitting – could mean energy savings of 70 – 90 percent versus 20 to 40 percent using subpar retrofit options.

The scientists also note that compact urbanization that includes green space and commercial or non-residential buildings leads to lower energy-use as cycling, walking and public transportation are realistic options.

Urge-Vorsatz is a professor in CEU's Department of Environmental Studies and Policy and leads CEU's Center for Climate Change and Sustainable Energy Policy. Gupta is a CEU PhD student who will graduate this year. Read the full paper here: