Sustainable urban cooling in the face of extreme heat

3 levels of urban cooling

According to the National Center for Hydro-Meteorological Forecasting, in the past month alone (from May 11 to June 10), there have been 5 widespread heat waves across the country. Notably, although the number of hot days did not last as long as in previous years, the daily temperatures were quite high with about 20 measuring points recording record temperatures, mainly in the North.

In urban areas, the inner city temperature is often higher than in the suburbs and neighboring rural areas, so people feel the effects of heat on their health more clearly, especially the elderly, children and low-income workers. According to the United Nations Environment Program (UNEP), cooling living and working spaces has become one of the essential needs of urban residents, leading to the demand for energy for this purpose being predicted to triple by 2050 compared to 2016. The heat island effect occurs due to high urbanization rates, high concentration of high-rise buildings, rapid increase of personal vehicles while green areas of trees and lakes are still scarce.

Heat-resistant solutions need to be integrated right from the infrastructure planning and urban design stages.

In the Guidebook for Sustainable Cooling Cities, UNEP identifies three levels of cooling that can be combined to create a system-wide approach: Reducing heat at the urban scale, reducing cooling demand in buildings, and serving cooling demand in buildings effectively. Explaining more specifically, Master Ngo Hoang Ngoc Dung - urban heat researcher (UNEP) said that on the urban scale, heat-resistant solutions will be integrated right from the infrastructure planning and urban design stages, focusing on reducing heat at the regional level, and nature-based solutions.

A typical example is the capital of South Korea, Seoul. The city government restored the Cheonggyecheon stream that flows through the area, replacing 5.8 km of elevated highway that covered the stream with a natural riverside corridor. Compared to a parallel road a few blocks away, this corridor reduced the temperature of this area by 3.3°C to 5.9°C. In Medellín, Colombia, from 2016 to 2019, the city created 36 green corridors on both roads and waterways, reducing the space in these areas by up to 4°C.

On the building scale, the design will focus on energy saving and efficient heat dissipation, raising the level to standards and regulations related to building energy and green buildings. Buildings owned by the city become models of sustainable cooling. A specific example is the Green Building of the Public Service Management Board of Dong Hoi City, Quang Binh Province. The entire building has a total area of walls and roofs covered with green up to more than 900m2, helping to effectively insulate in hot and sunny conditions without shade, reduce electricity consumption, filter dust and humidify the air, reduce the phenomenon of urban heat islands. At the same time, creating a highlight landscape for the ecological urban area of Dong Hoi City.

In Vietnam, the Climate Change and Sea Level Rise Scenario 2020 (Ministry of Natural Resources and Environment) indicates that the average annual temperature nationwide according to the highest emission scenario by the end of the century could increase from 3.2°C - 4.2°C.

Finally, UNEP recommends using efficient cooling technologies and equipment that are appropriate to the needs; adjusting living and working habits to minimize the amount of energy, emissions and waste heat generated by humans. The benefits of sustainable urban cooling are far-reaching, including improved health and labor productivity, reduced electricity requirements, reduced emissions and direct economic benefits - Mr. Dung commented.

Mainstreaming the implementation of climate change policies

Due to the requirements of construction standards, energy, greenhouse gas emission reduction, and climate change adaptation, there are currently five major policy groups related to urban cooling, including: Climate change, green growth, energy, housing development, and science and technology development. Regional localities promoting urban solutions will also simultaneously implement national strategies and plans related to these policy groups. The 2022 updated Nationally Determined Contribution (NDC) report also mentioned the importance of urban cooling in achieving Vietnam's climate change response goals.

According to Mr. Ha Quang Anh - Director of the Low Carbon Development Center (Department of Climate Change, Ministry of Natural Resources and Environment), about 20 provinces/cities have issued action plans to implement the Project on developing Vietnamese urban areas to respond to climate change in the period of 2021 - 2030, which initially mentions the content of urban cooling. More than half of the provinces/cities have energy regulations to implement legal regulations and policies on the use of energy economically and efficiently, and renewable energy.

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UNEP studies show that by the end of the 21st century, temperatures in many cities around the world could rise by as much as 4°C if greenhouse gas emissions continue to rise at their current rate. Even if the world achieves its goal of reducing greenhouse gas emissions to keep global temperature increases below 1.5°C, some 2.3 billion people will still be at risk of severe heatwaves.

38 central-level provinces/cities and 5 provincial-level cities have local green growth action plans, including tasks indirectly related to urban cooling. 38 provinces and cities have issued or drafted regulations related to the development of housing integrated with urban cooling, including green infrastructure solutions, low-emission construction materials, application of digital technology to manage building energy, standards on minimum green tree ratio, planning of natural landscapes in urban areas, etc. In addition, 22 provinces and cities have issued policies related to the implementation of the Science, Technology and Innovation Development Strategy with contents related to urban cooling.

Although the policy system has mentioned it, according to Mr. Quang Anh, the “content” of urban cooling is still low and has only been mentioned indirectly. Many localities pay full attention to integrating urban cooling measures into local planning and strategies, while to ensure effectiveness, there needs to be specific orientation to balance the potential of urban cooling solutions with other local development goals and priorities.

One of the current challenges is that the cooling sector has not really attracted private enterprises to participate, due to the lack of synchronous policies and support mechanisms for decentralized cooling solutions. Studies show that the State has not yet had a mechanism to combine many green cooling projects, leading to high implementation costs while low efficiency. In the immediate future, finance remains one of the main barriers to urban cooling projects and investments in the coming time.

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Integrating sustainable cooling into broader policy frameworks
As demand for cooling in cities has skyrocketed, integrating sustainable cooling into broader policy frameworks will help Vietnam take comprehensive action to protect people’s health in the face of escalating heat waves. GGGI will support Vietnam in analyzing the impacts of the cooling sector on climate change mitigation in its Nationally Determined Contribution (NDC) report, pursuing green growth goals.
Financing solutions for sustainable cooling include using grants and technical assistance programs to develop comprehensive urban planning, including long-term strategic plans, spatial plans, and climate action plans. In the long term, localities should strengthen long-term PPP approaches to finance capital-intensive sustainable infrastructure; deploy green bonds/loans, sustainability-linked bonds/loans, and transitional financial instruments to finance green buildings, innovative business models for energy efficiency, and sustainable cooling.
Vietnam can also create a viable business model for the energy efficiency market by accelerating the establishment of criteria and the development of a bankable green project portfolio, and by establishing dedicated trust funds to underwrite domestic and international financing and private sector investment in sustainable cooling projects.
Mr. Jason Lee - Deputy Director of Asia, Chief Representative of the Global Green Growth Institute (GGGI) in Vietnam

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Focus on natural heat dissipation design
The temperature from the outside environment is transmitted to the inside through the building envelope. This is the main cause of increased energy consumption for cooling in most types of buildings in Vietnam, so the design and selection of shell materials need to address the limitations, as well as take advantage of favorable conditions of the natural climate surrounding the building (microclimate design). The shape and orientation of the house must be designed to reduce solar radiation and catch cool winds, avoiding hot winds in summer and cold winds in winter. Create natural cross-room ventilation by organizing air intake and exhaust doors, preferably on two opposite walls or perpendicular to each other. Optimizing window sizes and choosing types of glass with low heat absorption coefficients will reduce the amount of heat transmitted into the interior space. Natural ventilation can also be effective in high-rise buildings if there is a design solution that ensures safety in conditions of relatively high wind speeds.
To avoid the phenomenon of heat island in urban areas, on the construction site, it is necessary to apply a combination of planting trees, making trellises or installing solar energy collection equipment on the roof to provide shade, using sun-shading structures or shading thanks to existing tree canopies, roofing materials with reflectivity >70%. Plant grass or use paving materials with a solar radiation absorption coefficient not exceeding 40%.
Dr. Architect Le Thi Bich Thuan - Former Deputy Director of the National Institute of Architecture

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Towards potential cooling measures
The Department of Climate Change is currently leading the implementation of the program “Sustainable Urban Cooling in Urban Areas in Vietnam”. In the period of 2022 - 2024, experts focus on analyzing the urban heat island (UHI) model across the city, focusing on typical months in the last 3 years (2020, 2021, 2022), clarifying temperature variations and increasing cooling equipment at the city and surrounding area scale. Activities aim to identify high-risk locations for urban temperatures, and at the same time, forecast future UHI and heat waves, along with potential cooling measures, including both outdoor and indoor levels.
On this basis, the Program will integrate and support Can Tho City and Tam Ky City (Quang Nam Province) to develop an Urban Cooling Action Plan, and at the same time, conduct a rapid assessment of readiness for the next investment phase on sustainable cooling in Dong Hoi City (Quang Binh Province). The Program will support localities in the Central Coast region to implement the NDC in adapting to climate change, while promoting investor attraction to support sustainable cooling solutions and combating extreme heat in urban areas in Vietnam.
l Ms. Nguyen Dang Thu Cuc - Deputy Head of Greenhouse Gas Emission Reduction and Ozone Layer Protection Department (Department of Climate Change, Ministry of Natural Resources and Environment)