New Study Shows Green Roofs Can Cool Cities and Save Energy


Extensive greenery coverage on rooftops of buildings has the potential to significantly reduce temperatures at the city scale and decrease energy costs, a new study has found. Led by researchers from Kyung Hee University and UNSW Sydney, the study analyzed the transformative effect of green roofs on urban-scale energy consumption and climate conditions, providing a template for modeling their potential in other cities worldwide.

Previous studies have only considered the energy impact of green roofs on individual buildings. However, this study is the first to evaluate the real climatic and energy impacts of green roofs at the city scale. The findings highlight the tremendous potential of green roofs to substantially decrease the peak temperature of a city and increase energy savings.

The study focused on Seoul, South Korea, a city heavily affected by urban overheating due to climate change and rapid urbanization. The researchers ran large-scale cooling climatic and building energy simulations using three greenery coverage scenarios to evaluate the potential of green roofs in lowering the temperature and cooling needs of the city during the hottest summer month, August. They specifically examined non-irrigated extensive green roofs, which are lightweight and have large-scale implementation potential with lower maintenance costs.

The modeling demonstrated that higher green roof coverage led to more significant decreases in temperatures and energy demand. When 90% of buildings were covered with green roofs, the city’s air temperature and surface temperature dropped by up to 0.54°C and 2.17°C, respectively. Building energy use also decreased by approximately 7.7% (0.64 kWh/m2).

Green roofs help cool temperatures by enabling evaporation through plant transpiration, which cools the surrounding air and reduces the need for mechanical cooling systems such as air conditioning. This ultimately lowers the overall energy demand. Furthermore, the layer of soil and vegetation on green roofs provides insulation, reducing heat transfer into buildings and further lowering energy costs.

Currently, green roof coverage in Seoul is modest, but it is expected to expand to between 30% and 60% based on local policies in the next few decades. However, the researchers believe that green roof coverage of 90%—the maximum potential—could be achieved with the right incentives.

Seoul is not the only city facing severe urban overheating; it is a major problem in the built environment worldwide. The study’s findings highlight the promising role of green roofs as a scalable nature-based solution to address the challenges of urban heat. By installing green roofs on new buildings and retrofitting existing ones, cities can mitigate the adverse effects of urban heat and reduce energy consumption.

This study provides valuable insights into the potential of green roofs to cool cities and save energy. Implementing green roof technologies on a large scale could make a significant contribution to creating more sustainable and comfortable urban environments. With the right policies and incentives, cities around the world can embrace the transformative power of green roofs and work towards a greener and cooler future.

1. Source: Coherent Market Insights, Public sources, Desk research
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