Hot summer day in a city. Looking for breeze of fresh air, relief for body and soul in greenery. Sounds familiar? Very recently, just few days ago the Olympic games 2024 in Paris ended. You might have already heard about serious issues facing future summer Olympics - by 2050, majority of cities will be too hot to host this unique sporting event. The same goes for other sporting events which are held in summertime. International Olympic Committee is already planning implementation of special heat protocols, from building the fountains and facilities for heat illnesses treatments, to planting the trees and shading buildings.
Picture 1: Sport events in summer are endangered due to heat waves (https://www.theguardian.com/sport/article/2024/jun/18/paris-olympics-2024-weather-summer-temperatures-extreme-heat ).
Clearly, the heat waves do not endanger only sporting events, but affect daily life and health of all of us. Some cities, like Austin in Texas, already apply heat protocols, by informing citizens about health risks and prevention measures during heat waves, together with the map of community cooling centres, where users can view locations and find directions to the nearest cooling centre.
This response to the climate extremes is commendable adaptation and worth to implement elsewhere too. But we should not forget to take all possible measures before the adaptation strategies, that is for prevention and moderation of heat waves.
Smart spatial planning as a frontrunner for moderation of heat waves
More than half of global population lives in cities. Urban settlements are of great importance in the context of global development since they house 55% of the world’s population, being projected by 2050 an increase to 68% (United Nations, 2019).
Exposure to high temperatures is amplified by the urban heat island effect, where buildings, concrete and other infrastructure trap heat. Density, air pollution, poverty and geography further increase the vulnerability of many people in cities. As urban areas continue to expand, the way we design and manage our cities can significantly impact our ability to mitigate and adapt to climate challenges. City spatial planning is therefore a crucial tool in the fight against climate change.
Picture 2: on the right – a parking lot. On the left – dinfferences in temperatures in this parking lot due to asphalt and cars (photo courtesy: UCAL study: Improving micro-climates in Los Angeles´ Heat Vulnerable Communities, 2016-2017).
Effective spatial planning can mitigate the extreme weather risks (floods, heatwaves, storms) by incorporating green infrastructure, such as parks, green roofs, green walls and urban forests, which help absorb rainwater, reduce urban heat islands, and improve air quality. For example, cities like Rotterdam and Antwerp have integrated climate adaptation strategies into their urban planning policies, creating more resilient urban environments (van der Berg, 2022).
Spatial planning plays a pivotal role in the implementation of green roofs. By strategically integrating green roofs into urban design, cities can unlock numerous environmental, economic, and social benefits. Spatial planning can mandate green roofs through zoning laws and building codes. Cities like Toronto and Copenhagen have successfully implemented policies requiring new buildings to include green roofs, thereby ensuring widespread adoption (Calheiros and Stefanakis, 2021). Public awareness campaigns and educational programs are also crucial. By highlighting the benefits of green roofs—such as improved air quality, reduced urban heat islands, and enhanced stormwater management—cities can encourage community support and participation.
Spatial planning is instrumental in promoting the implementation of green roofs. By leveraging policies, incentives, and public engagement, cities can harness the full potential of green roofs to build resilient, sustainable, and vibrant urban landscapes.
Photo 3: Extensive green roof with ecological, economical and aesthetic benefits (photo courtesy: Bentarchitecture https://www.bentarchitecture.com.au/articles/2019/whats-the-difference-between-an-intensive-green-roof-and-an-extensive-green-roof )
Green roofs for resilient communities
The importance of green roofs for future city resilience cannot be overstated. They act as natural insulators, reducing energy consumption for heating and cooling buildings. This not only lowers greenhouse gas emissions but also cuts energy costs for residents and businesses. Additionally, green roofs absorb rainwater, mitigating the risk of flooding during heavy rainfall events. This is particularly vital as climate change increases the frequency and intensity of such events. Sang et al. (2022) reports that green roofs play an important role when retrofitted in the dense urban environment (where space is limited) and spatially allocated to areas hosting groups vulnerable to heat exposures.
Some interesting research findings about green roofs and their impact on climate change from recent academic studies are listed below:
- Energy Savings: A study published in 2024 (Alilkhanova et al., 2024) found that green roofs can reduce urban building energy use intensity by up to 7.7% per month. This reduction is due to the cooling effect of green roofs, which helps lower the energy demand for air conditioning.
- Urban Heat Island Mitigation: Above mentioned research conducted in Seoul demonstrated that extensive green roof coverage could cool the city by approximately 1°C during summer and slash the energy demand associated with cooling by almost 8 per cent under maximum coverage. This cooling effect together with energy savings significantly reduces the urban heat island phenomenon, which is a major concern for cities worldwide.
- Stormwater Management: Green roofs play a crucial role in managing stormwater. They can absorb and retain rainwater, reducing runoff through evapotranspiration and delaying the runoff, and mitigating the risk of urban flooding. Further, green roofs can contribute to neutralization of acid rain. All of this is becoming particularly important as climate change increases the frequency and intensity of heavy rainfall events (Raimondi and Becciu, 2021).
- Biodiversity Enhancement: Green roofs provide habitats for various plant and animal species, contributing to urban biodiversity. They create green spaces in densely populated areas, offering a refuge for wildlife and enhancing the ecological health of cities (Urbanscape, 2021).
- Air Quality Improvement: By incorporating vegetation, green roofs help improve air quality in urban areas. Plants on green roofs can absorb pollutants and produce oxygen, contributing to a healthier urban environment (Xie et al. 2024).
Urbanscape extensive green roofs are usually covered with Sedum plants. Interesting fact is, that research study from 2019 (Schindler et al.) shows that extensive green roofs, covered only with Sedum plants, have greater cooling effect in Mediterranean climate zone then those green roofs which are covered with mix of Sedum and annual plants: “We found that temperatures below green roofs were around 7 °C cooler than below non-green roofs, and that temperatures below Sedum roofs were, in general, 1.5 °C cooler than below annuals + Sedum roofs. Overall, Sedum roofs appear to be more effective in providing cooling benefits in this climate, due to higher substrate moisture and vegetation cover in the summer. Thus, to achieve the cooling benefits of an extensive green roof in a Mediterranean climate, it may be prudent to use succulent species alone, without annuals that would compete with Sedum in winter, while not providing a cooling effect in summer.“
Photo 4: Blooming Sedum on Urbanscape green roof (photo: https://www.urbanscapegreenroofs.com/)
These findings highlight the multifaceted benefits of green roofs, making them a valuable strategy for cities aiming to enhance resilience and sustainability in the face of climate change. If you want to know exactly how much your Urbanscape green roof reduces energy bills by cooling effect in summer and thermal insulation effect in cooler period of the year, helps fighting heat island effect and manages the rainwater and stormwater on your roof, contact us for the report with our Performance Evaulation Tool: https://www.urbanscape-architecture.com/tools-documents/
Literature:
Alhilkanova, I., et al., 2024. Green roofs save energy in cities and fight regional climate change. Nature Cities 1, 238-249.
Calheiros, C.S.C., Stefanakis, A.I., 2021. Green Roofs Towards Circular and Resilient Cities. Circ.Econ.Sust. 1, 395–411.
Raimondi, A., Becciu G., 2021. Performance of Green Roofs for Rainwater Control. Water Resources Management Vol. 35, 00-111.
Sang, A. O., Thorpert, P., Fransson A., 2022. Planning, Designing and Managing Green Roofs and Green Walls for Public Health – An Ecosystem Services Approach. Front. Ecol. Evol., april 2022. Sec. Urban Ecology, Vol. 10.
Schindler, B.Y., et al., 2019. Cooling effect of Sedum Sediforme and annual plants on green roofs in Mediterranean climate. Urban Forestry and Urban Greening. Vol 38, 392-396.
Twohig, Cian T., Casali, Y., Aydin, N. Y. Can Green Roofs Help with Stormwater Floods? A Geospatial Planning Approach. Available at SSRN.
United Nations (2019) World urbanization prospects: the 2018 revision (ST/ESA/SER.A/420). Department of Economic and Social Affairs, Population Division. New York: United Nations.
van der Berg, A., Climate Adaptation Planning for Resilient and Sustainable Cities: Perspectives from the City of Rotterdam (Netherlands) and the City of Antwerp (Belgium). European Journal of Risk Regulation. 2023; 14(3): 564-582.
Urbanscape, 2021. How Urbanscape green roofs bring biodiversity back to cities.
https://www.knaufinsulation.com/news/how-urbanscaper-green-roofs-bring-biodiversity-back-to-cities
Xie, C., et al., 2024. Vicissitudes and prospects of green roof research: a two-decade systematic bibliometric review. Front. Ecol. Evol., January 2024. Sec. Urban Ecology. Vol. 11.
