'Vertical forests' help cool down urban areas.

From Milan (Italy) to Singapore, architects are transforming buildings into 'vertical forests' to combat the urban heat island effect – a phenomenon that makes cities up to 15°C hotter than rural areas.

The green spaces at Namba Parks, a nine-story shopping mall and movie theater complex in Osaka, benefit from abundant sunlight. - Photo: Nikkei Asia

Hanging gardens not only enhance the landscape but also absorb carbon, provide oxygen, and restore the connection between people and nature in urban areas.

2024 was recorded as the hottest year on record, with average temperatures rising 1.55°C compared to pre-industrial levels. With an estimated nearly 70% of the world's population living in cities by 2050, the question arises: how will cities "breathe" amidst their concrete and asphalt?

The "green" towers in Japan

The urban heat island effect turns cities into giant "furnaces." Not only during the day, but even at night, according to DW (Germany), central areas of London and Paris are about 4°C hotter than rural areas, leaving residents with little chance to rest after sweltering days.

The reason stems from the fact that concrete, asphalt, and high-rise surfaces store heat during the day and release it at night, while trees, which have the ability to naturally cool the environment, are becoming increasingly scarce.

To "cool down" urban areas, according to Nikkei Asia, Japanese architects have utilized rooftops and walls, transforming them into elevated gardens. A prime example is the Namba Parks complex in Osaka, where 70,000 trees and 300 plant species create a diverse ecological space in the heart of the city.

Similarly, in Tokyo, the 4,000m² garden on the 13th floor of the Ginza Six shopping center is divided into various areas such as grass, forest, and water, recreating the Japanese garden culture of the Edo period. Furthermore, the roof of Osaka Station, once a scorching hot surface, has been transformed into a natural living space with cherry trees, pine trees, and tamaryu grass, both cooling the area and attracting birds and insects.

The cooling mechanism here comes not only from the shade of trees, but also from the evaporation of water from the vegetation. According to climate experts speaking to DW, plants act as a natural air conditioner: they absorb water from the soil and release it into the air as water vapor, contributing to lower temperatures. Therefore, green roofs not only help city dwellers avoid extreme heat but also improve air quality, creating a more pleasant and sustainable living environment.

Nikkei Asia also mentioned the core philosophy of Japanese gardening: its essence is to maintain the connection between humans and nature, ensuring that this connection is not broken.

"Vertical forests," spreading from Milan to the globe.

While Japan showcased how hanging gardens integrated into East Asian urban culture, Europe gave birth to another iconic model: the Bosco Verticale twin towers in Milan. The structure, comprising two towers of 27 and 18 stories respectively, was designed by Italian architect Stefano Boeri and features 900 large trees and 20,000 shrubs covering its facades.

According to Parametric Architecture, the Bosco Verticale "forest" absorbs 30 tons of CO2 and produces 19 tons of oxygen annually _, equivalent to a forest spanning over 20 hectares. This is not just architecture, but a successful experiment on how buildings can "live" in harmony with nature.

From Milan, the idea of ​​"vertical forests" quickly spread to many places. In China, the Nanjing Vertical Forest project, with 800 large trees and 2,500 shrubs, helps reduce 18 tons of CO2 _and produce 16.5 tons of oxygen annually.

In Singapore, the Oasia Hotel achieved a green space ratio of 1,100%, transforming the skyscraper into a habitat for birds and insects. Meanwhile, in Sydney, Block 2, designed by French architect Patrick Blanc, incorporated 50% of the greenery from the adjacent park directly onto the building's facade.

However, these projects are not without challenges. According to Parametric Architecture, the initial construction costs are higher than those of conventional houses due to the need for specialized materials, structures, and plant care systems.

Furthermore, maintenance work, from watering and pruning to replacing dead trees, requires skilled technical personnel and long-term costs. But architects believe that long-term benefits such as energy savings, reduced pollution, and improved quality of life will far outweigh the initial costs.

The art of "growing trees in the sky"

Behind the lush greenery of these rooftop gardens lies a meticulous preparation process. In Milan, the plants for the Bosco Verticale project were "trained" for three years in a nursery in Como before being placed on the tower.

In Tokyo, architect Patrick Blanc studied plants that thrive in tropical forests lacking soil and sunlight to create "vegetation carpets" that cling to walls, according to Nikkei Asia. The Ginza Six department store in Tokyo chose seasonal trees, planting cherry blossoms to the north and red maples to the south to recreate the spirit of Edo.

In Singapore, the Oasia Hotel employs a "sandwich" strategy, creating multiple levels of sky gardens within a single building. Even the granite in the Canadian Embassy garden in Tokyo is hollowed out to reduce weight, an unprecedented practice in the past.

These projects are not just architectural solutions, but also a green revolution aimed at helping the city cope with extreme heat, reduce emissions, and restore natural breathing space for urban residents.

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Source: https://tuoitre.vn/rung-thang-dung-ha-nhiet-cho-do-thi-20250822102810245.htm