【Policy Address Series】If I were the Chief Executive, I would Enhance the Urban Greening
| Dave Wong, Communication Officer of Friends of the Earths (HK)
Hong Kong has been facilitating various urban
greening projects over the years, for example, greening the rooftops of government
buildings and streets, but the results were not satisfactory. According to the
"LCQ22: Green roof projects” on 3 June 2015,the government only focused on greening government buildings and primary and
secondary school premises, providing no financial assistance to property owners
of private buildings. Strengthening urban greening policies gives Hong Kong one
more tool, in addition to energy and carbon reduction, to improve air pollution
and other issues.
Greening Less Than Ideal?
Green roofs are one of the most common and
popular urban greening project. International cities all over the world have
included the concept of green roofs in urban or architectural planning. As
mentioned earlier in the article, Hong Kong's green roof planning lags behind
the world and needs to be improved. Take Japan for example. In 2001, Tokyo stipulated
that all new buildings require green roofs. For private buildings with a
construction area of more than 1,000 square meters and public facilities of 250
square meters, including new construction, renovation or all expansions require
more than 20% of the roof to be greened. In 2005, this extended to all of
Japan.In the West, such as Toronto, San Francisco and Germany, these places have
already included green roofs as part of urban planning practices.
In contrast, Hong Kong, as an international
metropolis, has not fully implemented the concept of green roofs. Although the
government has started to green roofs, the momentum was not enough to encourage
other facilities and buildings to adopt the concept. According to the 2020
report from the Hong Kong Green Building Council,about 1,600 private and public projects in Hong Kong have been registered with BEAM Plus certification—which requires buildings with more than 1,000 square meters to have
at least 20% green coverage. For those 1,600 private and public projects,
this represents 40% of the new buildings built since 2010, but it only accounts
for about 3.2% of the 50,000 existing buildings in Hong Kong.
to Cool Hong Kong?
Hong Kong is placed fourth in population
density.With a small area and a large population, the city is over concentrated with urban
development, making buildings excessively dense. The formation of dense
buildings and walled buildings makes it difficult for heat to be released back
to space. Also, the development of urban areas generates man-made pollutants
and heat, which easily lead to urban heat island. In fact, it is easy to find
out that the average temperature in Hong Kong has increased every year, from
21.5°C in 1885 to 24.5°C in 2020. The annual mean temperature rose by an
average of 0.13°C per decade from 1885 to 2020, but increased to 0.24°C per
decade during 1991-2020 in the latter half of the 20th century.In
addition, Hong Kong's roads are among the most heavily used in the world.Heavy vehicle emissions have also intensified heat island effect.
As such, it is necessary for Hong Kong to
fully integrate green roofs. According to the U.S. Environmental Protection
Agency, green roof temperatures can be 4°C cooler than typical roofs.Plants can regulate building temperature through evapotranspiration. The most
important point is that green roofs can reduce air conditioning demand and
greenhouse gas emissions (GHG). Therefore, green roofs can definitely cool and solve
Hong Kong’s heat island problem.
About Vertical Greening?
As mentioned above, green roofs are one of
the options for urban greening, which brings many benefits to the society. In
addition to greening the roof, vertical greening is also a good option. The
environmental benefits brought by vertical greening are very significant,
especially for heat dissipation. According
to the "Study of Vertical Greening Application” done by Drainage Services
Department, the temperature
of exterior walls can decrease by 7°C in the summer with vegetation cover. The green
wall also bring significant aesthetic and ecological benefits to the
surroundings and nearby residents.In another example, CUHK trialled green walls
in Yau Lai Estate and found that on hotter days, the difference between the
green wall and the original concrete wall can be as high as 16°C, and the indoor temperature difference is as high as 3.5°C. Utilizing the exterior
walls of buildings can make more use of the area of the building and not be
limited by the roof of the building.
Hong Kong for a Green Future
The concept of a green city is not well implemented
in Hong Kong, lacking in long-term planning. To tackle climate change and
achieve carbon neutrality, Hong Kong needs to catch up with international
standards on urban greening practices. Taking Singapore’s PARKROYAL COLLECTION Pickering
as an example, the design of the hotel takes references to terraces, planting more
than 20 plant species that can provide shading and adopting a large number of
environmental protection concepts such as green walls, artificial water
features, rainwater irrigation, and more. All of these equipment are also
powered with solar energy. Being
able to mix green elements into the design while taking into account of the
impact on the urban environment, Singapore's approach is worthy of Hong Kong's
reference. I believe that the city is capable of implementing green city
policies to turn itself into the leading green and low-carbon metropolis, meeting
carbon targets and even becoming an urban greening leader for other places.