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Globally 38% of energy-related CO2 emissions come from the construction sector. In China, it’s estimated to make up around a fifth of the country’s annual emissions, the second largest source. The sector shows more potential for reduction than the industry and transportation sectors.
With buildings, the carbon comes from two sources. There is embodied carbon which are the emissions related to construction, maintenance, and demolition. And then there is the carbon released from the usage of the building, typically through HVAC.
According to Eric Dempsey, architect and owner of Shanghai firm Dempsey Design Inc:
“The use of concrete is a huge emitter of CO2 as is the embodied carbon in glass and steel. Furthermore the lack of insulation in building construction is a major issue. Huge concrete towers soak up radiant solar energy and release it overnight. With minimal design improvements a significant amount of energy and resources can easily be saved.”
Refurbishment and Modernization
Under China’s 30-60 pledge, the country aims to peak CO2 emissions by 2030 and become a carbon-neutral economy by 2060.
Earlier this year, the Ministry of Housing and Urban-Rural Development published its fourteenth five-year plan (2021-2025) for the construction industry which insisted on greening the sector and highlighted the use of prefabrication and robots. The refurbishment of existing buildings rather than their demolition and replacement was also emphasized.
Dr. Jianli Hao, senior associate professor at the Department of Civil Engineering at Xi’an Jiaotong-Liverpool University says:
“One of the ways of achieving the objectives is by encouraging the refurbishment of existing buildings rather than demolishing old buildings and constructing new ones in their place. Under the Building Energy Efficiency and Green Building Development plan, it is proposed that by 2025, the area of energy-saving renovation of existing buildings will be over 350 million m2.”
Both energy efficiency and breaking the cycle of construction and demolition are crucial if China is to make a meaningful reduction in the sector. Since 2013 energy efficient buildings have been promoted. Studies put energy loss through walls from buildings in China at between 23% and 43%. Meanwhile, property consultancy Cushman & Wakefield puts the average lifespan of a building in China at just 35 years versus 74 years in the US and 132 years in the UK.
Hao explains what the changes are likely to mean in practice:
“With the Chinese government now emphasizing refurbishment instead of demolition and rebuilding, the average lifespan of a building in China is likely to reach its designed lifespan of 50 years.”
Plans call for the refurbishment and modernization of 219,000 old urban communities built before the year 2000.
Prefabricated Buildings
China’s green building market was valued at $178 billion in 2021 and had been growing at a compounded annual growth rate of 12.7% since 2017. The central government targets 70% of all new buildings to be green certified according to its standard by 2022.
On an internationally recognized standard, there are also concrete signs of improvement with China topping LEED certification (Leadership in Energy and Environmental Design) for a number of projects outside the US for six consecutive years. Shanghai saw 48% of Grade-A office buildings achieve LEED certification in 2020.
The five-year plan targets for around a third of new buildings to be prefabricated. One immediate benefit of this is less on-site waste with a target of 300 tons or less per hectare.
Prefabricated concrete components are suitable for different building types, and increase the integrated application of high-performance concrete, high-strength steel bars, energy dissipation and shock absorption, and pre-stressing technologies.
Hao explains mentioning that steel structure buildings are by their nature prefabricated.
Iot, Data and Robotics
China also intends to help green the industry using big data and the Internet of things. Robotics will also play a key role. Here Hao believes the industry is likely to see the most use of robots made in sensing, intelligent control and optimization, multi-machine collaboration, and human-machine collaboration.
China is actually no stranger to green construction techniques and until the modern era used them extensively. Allegedly millions of people still live in ‘caves’ in China. The homes, dug out from the loess plateau, offer natural insulation from the elements. Courtyard homes (siheyuan) such as the ones found in Beijing’s hutongs were also designed with the elements in mind. Here an inner courtyard is surrounded on all four sides by inward-facing buildings, the walls protecting the area from the harsh winter and sandstorms while absorbing winter sunshine.
In a more modern move to greening both new and existing buildings vertical green walls and green roofs are playing an increasing role.
According to Arcplus design institute landscape architect Alwin Li:
“Nature-based solutions are quite popular in China especially for landscape architects to green more urban areas and buildings to meet carbon sequestration goals.”
Such techniques help alleviate the urban heat island effect. With China’s new targets the country is seen as one of the five leading countries when it comes to green projects.
王若谷