Indira Adilkhanova, Mat Santamouris & Geun Young Yun of Nature Cities writes:

Cities around the globe search for solutions to tackle the challenges of climate resilience and energy consumption. The potential of green roofs representing a nature-based solution in mitigating urban heat and related energy consumption at the urban scale is given limited attention. Here we apply a comprehensive framework integrating urban climate modeling, urban building energy modeling and statistical analysis with empirical data to address this research gap through a case study in Seoul. The findings highlight that the efficacy of nonirrigated extensive green roofs is significantly influenced by meteorological conditions, underscoring the importance of considering those factors in green-roof design and implementation. Moreover, the cooling effect of green-roof implementation at the urban scale causes monthly urban building energy use intensity reductions of up to 0.64 kWh m−2 (7.7%). The insights from this research have broad implications for cities around the world experiencing the challenges imposed by urban heat.

New research shows rooftop greenery coverage can help cool down a major city while reducing energy demand.

Extensive greenery coverage on building rooftops could significantly reduce temperatures at the city scale and decrease energy costs, according to a new study.

The research, led by Indira Adilkhanova and Professor Geun Young Yun from Kyung Hee University and co-authored by UNSW Sydney Scientia Professor Mattheos (Mat) Santamouris, found that green roofs could cool South Korea’s capital city by around 1°C during summer and slash the energy demand associated with cooling by almost 8 per cent under maximum coverage.

The study, published in Nature Cities, is the first to analyse the transformative effect of green roofs on urban-scale energy consumption and climate conditions and could provide a template for modelling their potential in other cities worldwide.

“Previously, we have only looked at the energy impact of green roofs for singular buildings, but now this is the first study to evaluate the real climatic and energy impacts of green roofs at the city scale,” says Prof. Santamouris, the Anita Lawrence Chair in High-Performance Architecture at UNSW Arts, Design & Architecture. “Our findings demonstrate the tremendous potential of green roofs to substantially decrease the peak temperature of a city and increase energy savings.”

Prof. Santamouris specializes in developing heat mitigation technologies and strategies to cool cities affected by urban overheating. Seoul, South Korea, is one such city where climate change and rapid urbanization impact the magnitude of overheating issues, increasing energy consumption needs and adversely affecting health.

“One of the major problems in the built environment worldwide is severe urban overheating,” says Prof. Santamouris. “And as our cities heat up, thermal discomfort and heat-related illness and death also rise.”

Green roofs are a promising strategy for mitigating urban heat and energy consumption. With the ability to be installed on new buildings and retrofitted, they’re a scalable nature-based solution to address the challenges of urban heat.

Adilkhanova, I., Santamouris, M. & Yun, G.Y. Green roofs save energy in cities and fight regional climate change. Nat Cities (2024). https://doi.org/10.1038/s44284-024-00035-7

Read more: Modeling shows green roofs can cool cities and save energy